Yearly Archives: 2021

What is a PID controller?

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What is a PID controller?

A PID controller is an instrument used in industrial control applications to regulate temperature, flow, pressure, speed, and other process variables. PID is the abbreviation for proportional integral derivative. PID controllers use a control loop feedback mechanism to control process variables and are the most accurate and stable controllers.

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What is a PID controller?

What is meant by PID?

In the manufacturing process, if the equipment or space needs to be kept at a constant temperature, then PID is the best choice.
What is meant by PID?

P: Proportion, the input deviation is multiplied by a coefficient;
I: Integral, perform an integral operation on the input deviation;
D: It is differentiation, which performs a differential operation on the input deviation.

Mathematical description of PID:
u(t)=kp[e(t)+1/TI∫e(t)dt+TD×de(t)/dt].
Where
E(t) is the error signal;
U(t) is the output signal of the controller;
kp is the ratio coefficient;
TI is the integral time constant;
TD is the derivative time constant.

PID control is a kind of negative feedback control. Because in the feedback control system, the automatic regulator and the controlled object form a closed loop.

There are two possible situations when connected into a closed-loop: positive feedback and negative feedback.

The effect of positive feedback aggravates the imbalance of the inflow and outflow of the controlled object, resulting in system instability;

Negative feedback is to alleviate the imbalance, so as to correctly achieve the purpose of automatic control.

The instrument used in PID control is a PID regulator (also called a PID controller). Simply put, the PID control algorithm determines the price of the PID regulator. The temperature controller is also a kind of control algorithm that is more suitable for temperature control PID regulator. Its control algorithm is different from the regulator control algorithm commonly used for process control such as flow and pressure.

PID Controller Working Principle

PID controller, Promotion Integration Differentiation, that is, proportional-integral-derivative controller. It is mainly through the setting of three parameters Kp, Ki, and Kd. It is used to control the basic linearity and dynamic characteristics that do not change with time.

PID controller is based on the PID control principle to adjust the deviation of the entire control system. So that the actual value of the controlled variable is consistent with the predetermined value required by the process. Different control laws are applicable to different production processes. The corresponding control law must be selected reasonably. Otherwise, the PID controller will not achieve the expected control effect.

PID controller is a kind of feedback loop component that is very common in industrial control applications. This controller compares the collected data with a reference value. This difference is then used to calculate the new input value. The purpose of this new input value is to allow the system data to reach or maintain the reference value.

The PID controller can adjust the input value based on historical data and the occurrence rate of differences. This can make the system more accurate and more stable. It can be proved by mathematical methods. When other control methods lead to system stability errors or process repetitions, a PID feedback loop can keep the system stable.

Video source: https://www.youtube.com/watch?v=v27xYKdZUzI

PID Temperature Controller Working Principle

Proportional integral derivative (PID) controllers can be used as a means to control temperature, pressure, flow, and other process variables. As the name suggests, PID controllers combine proportional control with additional integral and derivative adjustments. Help the equipment to automatically compensate for changes in the system.

Computer-controlled thermostat: Using PID fuzzy control technology* Use advanced digital technology to form a fuzzy control to solve the problem of inertial temperature error through the combination of Pvar, Ivar, and Dvar (proportional, integral, derivative).

Many manufacturers often encounter the problem of inertial temperature error in the process of using the thermostat. Suffering cannot be solved, relying on manual pressure adjustment to control the temperature.

PID controller Applications

The PID controller is the most widely used controller. There are many digital pid algorithms.
PID controllers are mostly used for temperature control. But there are other more advanced and lower-level programs.

The PID regulator used by the instrument ranges from tens of yuan to tens of thousands of yuan. The difference lies in IO precision, type, algorithm complexity, operation speed, and additional functions.

The PID algorithm used by PLC is also different. Usually simpler than meters.

In the field of temperature control, there are PID meters, smart fuzzy meters, fuzzy PID meters, and even industrial computers.

If the temperature control also needs to control the temperature rise curve, then a simple PID meter is not suitable. A set value generator is also needed, and most intelligent thermostats with this function are built-in.

  1. Classic PID control algorithm regulator

For example, the accuracy is 0.5%. The intelligent regulator is used for process control such as pressure, flow, and liquid level to achieve good control effects. The temperature control effect is not good when used for temperature control.

  1. Fuzzy control algorithm regulator

Such as accuracy of 0.3%. The fuzzy PID regulator is used for pressure, flow, liquid level, and other process control effects. It is best for temperature control in plastic/food/packaging machinery, heating furnaces, and other industries with a constant temperature effect of ±1℃. PID parameter self-tuning effect is excellent It is the classic PID control algorithm regulator. The price of the two is the same.

  1. Artificial intelligence control algorithm regulator

Such as an accuracy of 0.2%. This artificial intelligence regulator is suitable for all automatic control sites and can achieve very good control effects. The best constant temperature effect for temperature control is ±0.1℃. The effect of PID parameter self-tuning is better than the adjustment of classic PID control algorithms and fuzzy control algorithms The price is slightly higher. Product performance is no different from European and American products.

  1. Temperature controller

Such as an accuracy of 0.2%. The temperature controller is dedicated to the temperature control of various large lag working conditions (such as kilns, electric furnaces). The temperature is constant and does not fluctuate. The performance is not much different from that of Japanese island power products. The cost is lower.

Related measurement and control instruments

You may like:

Sino-Inst offers over 10 PID controllers for Industrial data recording and analysis.

It is widely used in hydropower, tap water, petroleum, chemical, machinery, hydraulic and other industries to measure, display and control the pressure of fluid media on site.

A wide variety of PID controllers are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of PID controllers, located in China.

What is a pressure sensor?

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What is a pressure sensor?

A pressure sensor is a device that senses a pressure signal and converts the pressure signal into a usable output electrical signal according to certain rules.

Pressure sensors have a variety of structural types. Common types are strain gauge, piezoresistive, capacitive, piezoelectric, vibration frequency pressure sensors.

Pressure sensors are mainly used in booster cylinders. Pneumatic-hydraulic booster cylinder. Gas-hydraulic booster. Air conditioning and refrigeration equipment and other fields.

Get a Quote More Pressure Sensors

Types of pressure sensors

Pressure sensors can be classified according to the pressure range they measure, their operating temperature range or the type of pressure they measure. In terms of pressure type, pressure sensors can be divided into several major categories.

Absolute pressure sensors

Absolute pressure sensors measure pressure relative to an ideal vacuum pressure (0 PS or no pressure). With reference to vacuum, the atmospheric pressure at sea level is 101.325 kPa (14.7PSI).

Gauge Pressure Sensors

Gauge pressure sensors are used in different applications because they can be calibrated to measure pressure relative to a given atmospheric pressure at a given location. A tire pressure gauge is an example of a gauge pressure indication. More about: What is Diaphragm pressure gauge?

Vacuum Pressure Sensors

Vacuum pressure sensors are used to measure pressures that are less than atmospheric pressure at a given location.

Differential Pressure Sensor

A differential pressure sensor or transmitter measures the difference between two or more pressures introduced as inputs to a sensing unit. An example is the measurement of the pressure drop across an oil filter. Differential pressure is also used to measure the flow or level in a pressurized vessel.

Sealed Pressure Sensors

Extended reading: Featured Diaphragm Seal Pressure Transmitters

A sealed pressure transducer is similar to a gauge pressure transducer, except that it has been calibrated by the manufacturer to measure pressure relative to sea level pressure.

More about Industrial Pressure Sensors

Featured Pressure Sensors

SI-503K Gas Pressure Sensor
SI-702 High Pressure Sensor
SI-702S Ultra-High Pressure Senors
SI-512H High Temperature Pressure Sensor
High Frequency Dynamic Pressure Sensor
SI-706 Combined Pressure and Temperature Sensor-Dual function
SI-338 Ceramic Pressure Sensor
Absolute Pressure Transmitter
Hydrostatic pressure transmitter
Diaphragm Seal Pressure Transmitter
Diffused silicon Gauge Pressure Transmitter
Cryogenic Pressure Transducer

Working Principles of Pressure Sensors

Pressure Sensors are devices that convert various pressures into another physical quantity (usually electricity) that can be easily processed and transmitted according to certain rules. pressure sensors generally consist of three parts: a sensitive element, a conversion element and a measurement circuit, sometimes with an additional auxiliary power supply.

Extended Reading: Digital Pressure Sensor-RS485

Let’s look at the technology used in pressure sensors in more detail.

Pressure measurement technologies

Strain gauge pressure sensors are sensors that measure pressure indirectly by measuring the strain of various elastic elements. Depending on the material used to make them, strain gages can be divided into two categories: metal and semiconductor. The operating principle of strain gauge elements is based on the “strain effect” of conductors and semiconductors. This means that the resistance of conductors and semiconductors changes when they are mechanically deformed.

When a metal wire is subjected to an external force, its length and cross-sectional area will change. The resistance value will be changed. If the wire is elongated by an external force, its length increases. When the cross-sectional area is reduced, the resistance value increases.

When the wire is compressed by an external force, the length decreases and the cross-section increases, the resistance value decreases.

The strain on the wire can be obtained by measuring the change in voltage across the resistance.

Extended Reading: Resistive Pressure Transducer

A piezoresistive pressure sensor is a sensor made by using the piezoresistive effect of single-crystal silicon material and integrated circuit technology. The resistivity of single-crystal silicon material changes when it is subjected to a force, and an electrical signal output proportional to the change in force is obtained through the measurement circuit. It is also called diffusion silicon piezoresistive pressure sensor, which is different from the paste type strain gauge that needs to feel the external force indirectly through the elastic sensitive element, but directly through the silicon diaphragm to feel the measured pressure.

Piezoresistive pressure sensors are mainly based on the piezoresistive effect. The piezoresistive effect is used to describe the change in resistance of a material when subjected to mechanical stress. Unlike the piezoelectric effect, the piezoresistive effect only produces a change in impedance and does not produce an electrical charge.

Extended reading: Silicon Pressure Sensor

Capacitive pressure sensor is a pressure sensor that uses capacitance as a sensitive element to convert the measured pressure into a change in capacitance value. This kind of pressure sensor generally uses a round metal film or metal-plated film as an electrode of the capacitor, when the film feels the pressure and deformation, the electric capacity formed between the film and the fixed electrode changes, through the measurement circuit can output a certain relationship with the voltage of the electrical signal. The capacitive pressure sensor belongs to the class of

The capacitive pressure sensor belongs to the pole pitch change type capacitive sensor, which can be divided into a single capacitance pressure sensor and a differential capacitance pressure sensor.

Extended Reading: Smart pressure transmitter working principle

The piezoelectric pressure sensor is mainly based on the piezoelectric effect (Piezoelectric effect), using electrical components and other machinery to convert the pressure to be measured into electricity. Then the relevant measurement work measurement precision instrument. For example, many pressure transmitters and pressure sensors.

Piezoelectric sensors cannot be used in static measurements. The reason for this is that the charge can be saved only when the circuit has an infinite input resistance after an external force is applied. However, this is not the case in practice.

Therefore, piezoelectric sensors can only be used for dynamic measurements. The main piezoelectric materials are amine dihydrogen phosphate, sodium potassium tartrate, and quartz. It is in quartz that the piezoelectric effect is found.

Extended Reading: Electronic Pressure Switch for Air Compressor

Electromagnetic pressure sensors are a variety of sensors that use the electromagnetic principle collectively, mainly including inductive pressure sensors, Hall pressure sensors, eddy current pressure sensors, etc.

Inductive pressure sensors work due to different magnetic materials and magnetic permeability. When pressure is applied to the diaphragm, the size of the air gap changes. The change in air gap affects the change in inductance of the coil. The processing circuit can convert this change in inductance into a corresponding signal output for the purpose of measuring pressure.

This type of pressure sensor can be divided into two types according to the magnetic circuit change: variable reluctance and variable permeability. The advantages of inductive pressure sensors are high sensitivity and large measurement range; the disadvantage is that they cannot be applied to high-frequency dynamic environments.

Extended Reading: MEMS Pressure Sensors

Hall pressure sensors are made based on the Hall effect of certain semiconductor materials.

The Hall effect is the phenomenon that when a solid conductor is placed within a magnetic field and a current is passed through it, the charge carriers within the conductor are deflected to one side by the Lorentz force, which then generates a voltage (Hall voltage). The electric field force induced by the voltage balances the Lorentz force.

The polarity of the Hall voltage confirms that the current inside the conductor is caused by the movement of negatively charged particles (free electrons).

Pressure sensors based on the eddy current effect. The eddy current effect is produced by a moving magnetic field intersecting a metallic conductor or by a moving metallic conductor meeting perpendicular to the magnetic field. In short, it is caused by the electromagnetic induction effect. This action produces a current that circulates in the conductor.

The eddy current characteristic makes eddy current detection have characteristics such as zero frequency response, so eddy current pressure sensors can be used for static force detection.

Vibro pressure sensors are frequency-sensitive sensors, and this frequency measurement has a very high degree of accuracy. Because time and frequency are the physical parameters that can be measured accurately. And the frequency signal in the transmission process can ignore the influence of cable resistance, inductance, capacitance, and other factors.

At the same time, the Vibro-sinusoidal pressure sensor also has strong anti-interference ability, small zero-point drift, good temperature characteristics, simple structure, high resolution, stable performance, easy data transmission, processing, and storage. It is easy to realize the digitalization of the instrument. Therefore, the vibrating-sine type pressure sensor can also be used as one of the directions of sensing technology development.

Extended reading: Best Price Ceramic Pressure Sensor

Extended reading: Pressure indicator transmitters

Pressure sensors, pressure transducers, and pressure transmitters

A pressure sensor is a device or device that can sense a pressure signal and convert the pressure signal into a usable output electrical signal according to a certain rule.
A pressure sensor usually consists of a pressure-sensitive element and a signal processing unit. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors. A pressure sensor is the core part of pressure transmitter.

In a pressure transducer, a thin-film or piezo-resistive pressure sensor is mounted on a process connection. The transducer converts pressure into an analog electronic output signal, typically as a millivolt per volt output. These signals are not linearized or temperature compensated.

A pressure transmitter has additional circuitry that linearizes, compensates, and amplifies the signal from a transducer. The different signal types are typically voltage signals (eg, 0 to 5 or 0 to 10 volts), milliamp (eg, 4 to 20 milliamp), or digital. The instrument can transmit the signal to a remote receiver.

Extended reading: Static pressure vs dynamic pressure vs total pressure

Pressure sensor performance parameters

Pressure sensors mainly have the following parameters.

1.Capacity.

The range refers to the rated load of the pressure sensor. The general unit is KGf, N, etc.. Such as the range of 100KGf, the sensor measurement range is 0-100KGf.

2. Rated output.

Sensitivity is the output signal coefficient of the pressure sensor, the unit is mV / V, common 1mV / V, 2mV / V, the full range of the pressure sensor output = working voltage * sensitivity, for example: working voltage 5VDC, sensitivity 2mV / V, the full range of output that is 5V * 2mV / V = 10mV, such as pressure sensors full range of 100KG, pressure full 100KG, the output that is 10mV, pressure 50KG that is 5mV.

3. Non-linearity.

Non-linearity is the percentage of the maximum deviation between the output value of the empty load and the output value of the rated load determined by the straight line and the actual measured curve of the increased load for the rated output value. In theory, the output of the sensor should be linear, but in fact it is not. Non-linearity is the percentage deviation from the ideal. Non-linear units: %FS, non-linear error = range * non-linearity, such as the range of 100KG, non-linearity of 0.05% FS, non-linear error that is: 100KG * 0.05% = 0.05KG.

4. Repeat ability.

Repeatability error refers to the repeated loading of the sensor to the rated load and unloading under the same environmental conditions. The maximum difference of the output value on the same load point during the loading process on the percentage of rated output.

5.Creep.

Creep refers to the load remains unchanged, other test conditions also remain unchanged, the pressure sensor output change over time on the percentage of rated output, generally taken 30min.

6.Hysteresis.

Hysteresis refers to the pressure sensor from no load gradually loaded to the rated load and then gradually unloaded. In the same load point on the maximum difference between the loaded and unloaded output on the rated output value of the percentage.

7. Zero balance.

Under the recommended voltage excitation, the output value of the pressure sensor at no load is a percentage of the rated output. Theoretically, the output of the pressure sensor at no load should be zero, in fact, the output of the pressure sensor at no load is not zero, which there is a deviation, zero output is the percentage of deviation.

8.Input resistance.

Input resistance is the signal output open circuit, the sensor is not pressurized, from the pressure sensor input (Cang positive pressure sensor for the red and black line) measured impedance value.

9.Output resistance.

Output resistance is a short circuit at the input of the pressure sensor, the sensor is not pressurized, the impedance measured from the signal output (Cangzhou pressure sensor for the green and white lines).

10.Insulation impedance.

Insulation impedance is the DC impedance value between the circuit of the pressure sensor and the elastomer.

11.Operation Temp range.

Operating temperature range refers to the pressure sensor in the temperature range of its performance parameters will not produce permanent harmful changes.

12. Compensated temp range.

Temperature compensation range refers to the temperature range, the rated output of the sensor and zero balance are closely compensated, so as not to exceed the specified range.

13. Temperature effect on zero.

Temperature effect on zero refers to the effect of changes in ambient temperature on the zero point of the pressure sensor. Generally used for every 10 ℃ change in temperature, the amount of change in zero balance caused by the percentage of the rated output to express, the unit: % F.S./10 ℃.

14. Temperature effect on out.

Sensitivity temperature drift is the change in the sensitivity of the pressure sensor caused by changes in ambient temperature. Generally expressed as a percentage of the rated output for each 10 ℃ change in temperature caused by the change in sensitivity, the unit is: F.S./10 ℃.

15. Safe Load Limit.

Safe overload means that the load will not cause destructive damage to the pressure sensor, but can not be overloaded for a long time.

16. Ultimate overload.

Ultimate overload is the limit value of the pressure sensor load.

17. Excitation voltage Excitation recommend.

Excitation voltage refers to the working voltage of the pressure sensor, generally 5-12VDC.

Extended Reading: Up to 800°C High Temperature Pressure Sensor

Applications of Pressure Sensors

Pressure sensor is one of the most commonly used sensors in industrial practice. It is widely used in various industrial self-control environments. It involves water conservancy and hydropower, railroad transportation, intelligent building, production automation, aerospace, military, petrochemical, oil well, electric power, ship, machine tool, pipeline and many other industries.

The following is a brief introduction to some application examples of pressure sensors.

  1. Application to hydraulic system

Pressure sensor in the hydraulic system is mainly to complete the closed-loop control of the force. When the control valve spool moves suddenly, a spike pressure of several times the working pressure of the system will be formed in a very short period of time.

  1. Pressure sensors in the application of water treatment

China’s environmental protection water treatment industry, in recent years, has been rapid development, and the future prospects are promising. Water and wastewater treatment processes rely on the use of pressure sensors to provide an important means of control and monitoring for system protection and quality assurance.

  1. Application in injection molding

Pressure sensors have an important role in injection molds. Pressure sensors can be installed in the nozzles of injection molding machines, hot runner systems, cold runner systems and mold cavities to measure the plastic pressure somewhere between the nozzle of the injection molding machine and the mold cavity during the injection, filling, holding and cooling processes.

  1. Applications in compressors, air conditioning and cooling equipment

Pressure sensors are commonly used in air compressors and air conditioning and refrigeration equipment. These sensors are compact and easy to install, and the pressure guide port is usually designed with a special valve needle.

  1. Used in monitoring mine pressure

Sensor technology as one of the key technologies for mine pressure monitoring.

On the one hand, we should properly apply the existing variety of sensors to serve the mining industry;

On the other hand, sensor manufacturers develop and develop new pressure sensors to adapt to more mining industry applications.

Note that the pressure transmitter needs to be calibrated after a period of use. In order to ensure the accuracy of the quantity.

FAQ

A proximity sensor is a device that has the ability to sense the proximity of an object… It uses the sensitivity of the displacement sensor to the approaching object to identify the proximity of the object. And output the corresponding switch signal. Therefore, the proximity sensor is often referred to as a proximity switch.

It is a general term for a sensor that replaces a contact detection method such as a switch for the purpose of detecting an object without touching it. It detects the movement and presence of the object and converts it into an electrical signal.

Proximity sensor, also known as contactless proximity sensor, is the ideal electronic sensor quantity proximity sensor.

When the metal detection body close to the sensor sensing area. The sensor can be no contact, no pressure, no spark, rapid electrical command. Accurate response to the position and travel of the motion mechanism. Even for general travel control, the positioning accuracy, operating frequency, service life, ease of installation and adjustment, and the ability to adapt to harsh environments are incomparable to those of general mechanical travel sensors. It is widely used in machine tool, metallurgy, chemical, light textile and printing industries.

Translated with www.DeepL.com/Translator (free version)

A differential pressure sensor is a sensor used to measure the difference between two pressures, usually at the front and rear ends of a piece of equipment or component.

Extended reading: Differential Pressure Transmitter Installation Guide

Oil pressure sensor is a device that converts pressure signals into electrical signals through the piezoresistive effect.

Oil pressure sensor is one of the most commonly used sensors in industry. It is widely used in various industrial automatic control environments, involving water conservancy and hydropower, engineering machinery, aerospace, transportation, petrochemical, machine tools, pipelines and many other industries.

Extended reading: High Pressure Hydraulic Flow Meter

As an important part of hydraulic equipment, the pressure sensor is used for pressure measurement and control. It can accurately measure the pressure to be measured and transmit the test results to the subsequent display or control in a timely manner.

Extended reading: Miniature Pressure Switch

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What is a pressure sensor? and other questions about pressure sensors. We hope that after reading this article, you will have a clear understanding.

Sino-Inst offers over 20 Pressure sensors. A wide variety of Pressure sensors options are available to you. Such as free samples, paid samples.

Sino-Inst is a globally recognized manufacturer of Pressure sensors, located in China. Sino-Inst sells through a mature distribution network that reaches all 30 countries worldwide. Pressure sensors products are most popular in Europe, Southeast Asia, and Mid East. You can ensure product safety by selecting from certified suppliers. With ISO9001, ISO14001 certification.

Water depth sensor- Water level sensor Solutions

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How do you measure the depth of water?

Water depth sensors are also known as water level sensors. Water depth sensors are often used to measure tank levels, well depths, river depths, etc. There are many different types of water depth sensors. All of them are used to measure the water level by submerging underwater or above the water surface. Then, they are converted into a water depth or water level signal. For example, submersible hydrostatic level meter, ultrasonic level meter, etc.

RFQ More level sensors

At present, the common measurement principle of liquid level meter in the industry involves mechanics, thermal, electrical, optical, and other aspects. The product models even reach hundreds of kinds. Of course, different types of level meters mean that they are produced, used, and calibrated in different ways. It is not possible to fit all measurement environments.

Water Depth/Level Sensors Types

The following will be from the perspective of the measurement method, for the current market more than ten kinds of liquid level meter classification. To help users in the selection of products to make the appropriate choice.

Water Depth Sensors measured by buoyancy

The buoyancy type level meter has a float (float ball or float). The float is in equilibrium on the static liquid level. When the liquid level changes, the float is displaced with the liquid level. The electronic component acquires the float displacement in a certain way. And then converted to the liquid level change.

Due to the different ways of receiving float displacement by electronic components, the buoyancy method liquid level meter is divided into magnetic flap level meter, float level meter, magnetostrictive level meter, etc.

Magnetic level meter consists of magnetic float, cylindrical container, scale and transmitter.

The float moves with the liquid level in the container, and the magnetic field of the float acts on the sensor. The sensor is a strip of rubber-sealed in a stainless steel tube of equal length to the measured liquid level. There are numerous reed switches welded to it at intervals of 1cm or less.

When the reed switch is at the same level as the float, it closes. Otherwise, the transmitter receives the current signal generated by the amount of resistance connected to the reed switch, which is converted to the liquid level.

Float movement is shown on the scale as a red and white bead flip, indicating the liquid level.

Extended reading: Water Tank Level Controller

Float level meter has a float, spring, magnetic steel chamber and indicator, designed according to Archimedes’ law and magnetic coupling principle.

The displacement of the float causes the magnetic field of the magnet chamber to change. The magnetic sensor inside the indicator precisely measures the change of the surrounding magnetic field.

Float Level Sensors – Single and Multipoint

The magnetostrictive level meter is mainly composed of float, waveguide, and transmitter.

The electronic component of the transmitter generates a low-voltage current pulse, which starts timing and generates a magnetic field that propagates down the magnetostrictive line.

The float moves along the measuring rod as the level changes, and the magnet inside the float also generates a magnetic field. When the two magnetic fields meet, the magnetostrictive lines are twisted to form a torsional stress wave pulse. The velocity of the pulse is known, and the pulse propagation time is calculated to correspond to the exact change in the liquid level.

Magnetostrictive Level Transmitters

Extended reading: Magnetostrictive Hydraulic Cylinder Position Sensor

Liquid level meter measured by pressure

The level meter of pressure method is the level meter that reflects the liquid level by measuring the liquid pressure through its pressure measuring element. It is generally composed of transmitter, sensor and pressure probe. The sensor is a special metal rod or cable with a built-in capillary hose, and the probe is constructed as a stainless steel cylinder core with a diaphragm at the bottom.

The probe intrudes into the liquid and tests the difference between the static pressure of the liquid and the actual atmospheric pressure, which varies with the liquid level. The electronic components receive the differential pressure signal to reflect the change in liquid level. According to the different materials of sensors are divided into two types of rod and cable type.

Rod type pressure level meter sensor is a metal rod. Its general technical parameters are, the measurement range is generally 0 ~ 5m, output signal: (4 ~ 20) mA, measurement accuracy is generally ± 0.5%.

SMT3151TR Submersible Level Transmitter
Hydrostatic level transmitter is also called hydrostatic level gauge. The rod-type Hydrostatic level transmitter 4-20mADC standard signal output. Flange or threaded installation. Can withstand high temperatures up to 450 ℃.

Because the sensor is a cable, can be bent, convenient handling and loading, so the range of the cable type pressure level meter can be very large, there are 100m, or even 300m, its measurement accuracy is generally ± 1.0%.

SI-151 Hydrostatic Level Sensor
Hydrostatic Level Sensor (Best Price), also called Hydrostatic level transmitter. Continuous level measurement in liquid applications with pressure sensors.

Differential pressure level meter is also through the detection of pressure differences to measure the liquid level.

The level meter has two pressure-taking ports in the gas phase and liquid phase.

The pressure at the gas phase pressure point is the pressure of the gas phase in the equipment. The pressure at the liquid phase pressure point is not only affected by the gas phase pressure, but also by the static pressure of the liquid column.

The difference between the liquid phase and gas phase pressure is the static pressure generated by the liquid column, which is converted into the liquid surface height.

Flange Mounted Differential Pressure Transmitter
Extended Diaphragm Seal DP Level Transmitter
Remote Seal Differential Pressure Transmitter
Differential pressure(DP) level transmitter

Liquid level meter measured by reflection

At present, there are two main types of reflective level meters: radar level meter and ultrasonic level meter. Their principles are basically the same, they are through the emission – reflection – reception of ultrasonic or electromagnetic wave (radar wave) way to measure the liquid level height.

Radar level measurement uses Non-contacting radar technology for Continuous level measurement. Liquids and solids are commonly measured with this measuring technique.

Radar level transmitters use radar technology to perform non-contact continuous level measurement. The radar level indicator converts the level into an electrical signal. The level signal output can then be utilised by other instrumentation to monitor or control. Liquids and solids are commonly measured with this measuring technique. Like: Fly ash silo. Radar level sensors are divided into: Pulsed radar technology and frequency modulated continuous wave (FMCW) radar level sensors.

Sino-Inst produces a 120GHz FMCW radar level sensor, 26GHz radar level meter, 6GHz level meter.

Extended reading: Radar Level Meter for Corrosive Liquids

Extended reading: Radar Water Level Sensor Applications

Ultrasonic Level Sensing sensors and transmitters are used for continuous, non-contact level measurement.

Ultrasonic Level Sensing is a low-cost liquid level measurement technology. Ultrasonic Level Sensing sensors and transmitters are used for tank or river level measurement. Ultrasonic Level Sensing does not need to contact the medium, can be continuously measured at low cost. Therefore, Ultrasonic Level Sensing is very popular among users. Ultrasonic liquid level sensors are available in general and intrinsically safe types. Output 4~20mA standard signal or output the measurement result to the secondary meter through RS-485. Meets the system’s automatic control.

Extended Reading: Wireless Water Meter

Liquid level meter through the conductive method of measurement

Level meters in the conductive mode are based on the electrical principle. The level is measured by means of measuring capacitance or resistance. This type of level meter mainly includes capacitance level meter, radio frequency conductivity level meter, resistance level meter.

The Capacitance level meter uses the change of measuring capacitance to measure the level of the liquid.

By a metal rod inserted into the liquid container, the metal rod is a pole of capacitance, the container wall is the other pole of capacitance. The medium between the two electrodes is the liquid and the gas above it.

As the dielectric constant of the liquid and the dielectric constant of the gas on the liquid surface is different, the level of the liquid is measured by the change of the capacitance between the two electrodes.

Extended reading: Capacitive water level sensor

RF conductivity level meter is an upgraded version of capacitance level meter, which can be understood as measuring conductivity with high frequency radio waves.

When the instrument works, the sensor of the instrument and the filling wall, and the measured medium form the conductivity value. When the level changes, the conductance value changes accordingly. The circuit unit converts the measured conductance value into a level signal output. To achieve the level measurement.

Extended reading: Radar Non Contact Water Level Sensor

Deep Well Water Level Sensor

Deep Well water level sensor is to apply Hydrostatic Level Sensor to deep well. The Well water level sensor submerged in deep well works together with a submersible water pump. The range within 300m ～ 1000m.

Deep Wells Water level sensor is based on the principle that the measured liquid pressure is proportional to the height of the liquid. The piezoresistive effect of the advanced foreign isolated silicon diffused sensor is used. Change to electrical signal. After temperature compensation and linear correction, convert to 4-20mA standard electrical signal. Well water level sensor submerged in deep well work together with water pump. It is extremely difficult to replace and submit an inspection. Therefore, it adopts stainless steel cable, waterproof, sealing ring, and other four-level seals. Special cables and special water sealing technology make the transmitter highly reliable and stable.

Extended Reading: 3 inch (3″) Water Flow Meter

Portable Ultrasonic Water Depth Gauge

Water Depth Gauge is a portable water depth detector based on the principle of ultrasound. Ideal water depth measuring instrument for ships, oceans, reservoirs, lakes, rivers, and shallow water level monitoring.

Water Depth Gauge is a necessary instrument to measure water depth in reservoir, lake, river, shallow sear. Place ultrasonic transducer on water surface or into a certain position into water. The device can caculate current water depth. HS-SFCC Portable Ultrasonic Water Depth Gauge It has perfect water depth measurement function. Control function, data transmission function and man-machine communication function. This machine integrates ultrasonic transceiver sensor, servo circuit, temperature compensation sensor and compensation circuit unit, display, control signal output and serial data or analog output unit (optional) as a water depth measuring instrument. It has the characteristics of low maintenance, high reliability, long life, convenient use, simple operation and accurate measurement. Therefore, it is widely used in water area monitoring.

Read more about: Common River Water Level Measurement Methods

How do you measure water level in tank with sensor?

The Water Tank Level Sensor is an important part of the water tank level control system. Using a level sensor for the water tank, solenoid valve, control box, liquid level switch and other accessories can effectively form a Water Tank Level control system. Monitor the materials stored in the water tank. Master important data such as its liquid level, reserves, and quality. A reasonable liquid level can ensure the safe, reliable, and efficient operation of the storage tank.

Read more about: Water Tank Level Sensors for Level Control

More Level Measurement Solutions

Sino-Inst offers over 20 Water depth sensors for level measurement.

About 50% of these are liquid level meters, 40% is the tank level sensor.

A wide variety of Water depth sensors options are available to you, such as free samples, paid samples.

Sino-Instrument is a globally recognized supplier and manufacturer of level measurement instrumentation, located in China.

How to Select Ultrasonic flow detectors?

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What is an ultrasonic flow detector?

An ultrasonic flow detector is often understood as an ultrasonic flow meter or ultrasonic transducer. In fact, an Ultrasonic flow detector refers to the probe part of the ultrasonic flow meter or sensor part. Ultrasonic flow detectors can be equipped with different ultrasonic flow detectors to meet different measurement needs. For example, a portable ultrasonic flowmeter can be equipped with a clamp Ultrasonic flow detector. commonly used in water, oil, and other single liquid flow rate detection.

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Ultrasonic flow detectors types

Ultrasonic flow detectors can be divided into external paste type, insertion type, and pipe section type according to the installation method.

A) Clamp-on type

External paste type ultrasonic flowmeter is produced earlier, the user is more familiar with and more widely used ultrasonic flowmeter. Installation of the transducer without pipeline disconnection. That is posted that use, it fully embodies the ultrasonic flowmeter installation is simple, easy to use characteristics.

Extended reading: Portable ultrasonic flow meter for water

B）Pipe section type

Certain pipelines due to material sparse, poor sound conduction, rust and corrosion is serious. Lining and pipeline space with gaps and other reasons. Resulting in serious ultrasonic signal attenuation. Ultrasonic flowmeter with external paste type can not be measured normally. Generated the pipe segment ultrasonic flowmeter.

Pipe segment ultrasonic flowmeter to the converter and measuring tube composition as a whole, to solve the external paste flowmeter measurement in a problem. Measurement accuracy is also higher than other ultrasonic flowmeter. But at the same time also sacrificed the advantages of the external paste type ultrasonic flowmeter non-flow installation. Requires the installation of the transducer to cut the pipe.

Extended Reading: Inline Ultrasonic Flow Meter

C) Insertion type

Insertion type ultrasonic flowmeter in between the above two. Installation can be non-stop flow, the use of special tools have water pipes on the hole, the transducer into the pipe, complete the installation. Transducer pipeline, its signal emission, receiving only the measured medium. Its measurement is not limited by the pipe quality and pipe lining materials.

TM series standard clamp-on Ultrasonic flow detectors

  • With a strong magnet, when measuring steel and cast iron pipes, the sensor only needs to be adsorbed on the outer wall of the pipe.
  • Equipped with a ground terminal, can be used in the occasion of strong electromagnetic interference.
  • Can be fixed by a steel belt, steel wire rope, tensioning belt, special clamps.
  • The upper cover of the sensor is marked with the direction of ultrasonic signal emission.
  • The protection level can reach IP68 after the junction box is filled with glue.
  • Complete specifications, divided into large, medium, and small models, measuring pipe diameter range: DN15~DN6000mm.
  • Temperature range: -40~90℃.
  • According to the different uses, the standard clamp-on sensors are divided into two categories: portable and stationary.

1 Tensioning belt fastening groove
2 Wire rope fastening groove
3 Steel belt fastening slot
4 Top cover fastening screw
5 Signal emission direction indication arrow
6 Sound wedge
7 Powerful magnets
8 Anti-slip groove

9 Upstream and downstream sign sticker
10 Cable interface
11 Installation distance measurement starting and ending points
12 Product information label
13 Positive terminal block
14 Negative terminal block
15 Ground terminal block
16 Junction box

Clamp-on Ultrasonic Flow Meter Working Principle

Clamp on Ultrasonic Flow Meter adopts the measurement principle of time difference method. It uses the ultrasonic wave emitted by the sensor to propagate in the flowing fluid. The sound wave propagation speed in the downstream direction will increase, and the backward direction will decrease. In the same propagation distance, there will be different transmission times. According to the difference between the transmission time and the measured The relationship between fluid velocity measures the fluid velocity.

The flow rate of the fluid is different in different positions in the tube. The flow rate in the center of the tube is faster than the flow rate near the wall of the tube. The flow velocity distribution of the fluid in the pipeline can be represented by the flow velocity cross-sectional distribution diagram.

By setting the flowmeter and considering the cross-sectional distribution of the flow velocity, the average flow velocity can be calculated. Then the volume flow of the fluid can be obtained according to the cross-sectional area of the pipe.

Notes:
V measure fluid velocity
M ultrasonic reflection times
D pipe diameter
θ The angle between the ultrasonic signal and the fluid
T up The time when the downstream sensor transmits the signal to the upstream
T down Time from upstream sensor to downstream
ΔT = T up – T down

Guess You’ll Like: Ultrasonic flow meters types & technical guide

HT series high temperature clamp-on ultrasonic flowmeter sensor

  • With high temperature resistant powerful magnet, when measuring steel and cast iron pipes, the sensor only needs to be adsorbed on the outer wall of the pipe.
  • Equipped with ground terminal, can be used in the occasion of strong electromagnetic interference.
  • Can be fixed by steel belt, steel wire rope, tensioning belt, special clamps.
  • The upper cover of the sensor is marked with the direction of ultrasonic signal emission.
  • The protection level can reach IP68 after the junction box is filled with glue.
  • Complete specifications, divided into large, medium and small specifications, measuring pipe diameter range: DN15~DN6000mm,
  • Temperature range: -40~160℃.
  • According to the different uses, high temperature clamp-on sensors are divided into two categories: portable and fixed.

1 Tensioning belt fastening groove
2 Wire rope fastening groove
3 Steel belt fastening slot
4 Top cover fastening screw
5 Signal emission direction indication arrow
6 Sound wedge
7 Powerful magnets
8 Anti-slip groove

9 Upstream and downstream sign sticker
10 Cable interface
11 Installation distance measurement starting and ending points
12 Product information label
13 Positive terminal block
14 Negative terminal block
15 Ground terminal block
16 Junction box

Extended reading: Flow Totalizer F3000X for Data collection and calculation

Other commonly used ultrasonic flow detectors:

What Does an Ultrasonic Doppler Flow Detector Measure?

From the ultrasonic measurement principle, the time difference method is suitable for measuring pure and less impurity liquids. Such as tap water, river seawater, sewage treatment plant effluent, etc. The Doppler method is suitable for measuring liquids and slurries with a high impurity content. Such as urban drainage, mud, pulp and so on.

Judging from the company’s years of practical experience, the two measurement methods are relatively vague for the quantitative indicators of the impurity content of the measured medium. The main reason is that there is currently no effective instrumentation for measuring the impurity content of liquids.

Doppler ultrasonic flowmeter flow rate measurement is based on the Doppler effect. The probe emits a beam of ultrasonic waves obliquely upward. Ultrasound propagates in fluids. The fluid will contain impurities such as bubbles or particles (it can be considered that the impurities in the fluid are at the same speed as the water flow).

When the ultrasonic wave contacts the impurities in the fluid, the reflected ultrasonic wave will produce a Doppler frequency shift Δf. The Doppler shift Δf is proportional to the flow velocity. The flow velocity of the fluid can be measured by measuring the Doppler frequency shift Δf.

The Dopp ultrasonic flowmeter uses the velocity area method to measure the flow. The flow velocity V is measured using an ultrasonic flow velocity sensor. Use a pressure water level gauge to measure the water level H. The channel parameters set in the controller in advance. The controller can use the water level to automatically convert the flow area S. The formula for the flow rate of the fluid is:

Q= V×S

Wherein V- – – -flow velocity S- – – -flow area Q- – -instantaneous flow

Since the velocity area method is used to measure the flow, it can be applied to any shape of the section.

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FAQ

Ultrasonic flowmeter refers to a flowmeter developed based on the principle that the propagation velocity of ultrasonic waves in the flow medium is equal to the average flow velocity of the measured medium and the vector sum of the velocity of the sound waves in the stationary medium.

According to the principle of signal detection, ultrasonic flowmeter can be divided into propagation speed difference method (direct time difference method, time difference method, phase difference method and frequency difference method), beam shift method, Doppler method, mutual correlation method, spatial filtering method and noise method, etc.

Our time difference ultrasonic flowmeter: measuring the time difference caused by the difference in propagation velocity when propagating downstream and upstream to calculate the measured fluid velocity.

The measurement accuracy of the ultrasonic flowmeter is very high. Almost no interference from various parameters of the measured medium.

Sino-Inst manufactures and supplies ultrasonic flow meters with an accuracy of 1%. This accuracy can meet the measurement needs of most customers.

In particular, it can solve the flow measurement problems of strong corrosive, non-conductive, radioactive and flammable and explosive media that other instruments cannot.

So what causes the inaccurate measurement of the ultrasonic flowmeter?

The following are the reasons for the inaccurate measurement:
The influence of pipeline parameter equipment on the accuracy of ultrasonic flowmeter measurement.
The influence of upstream and downstream straight pipes on the accuracy of ultrasonic flowmeter measurement.
The influence of couplant on measurement accuracy.
The influence of the installation position of the ultrasonic flowmeter transducer on the measurement accuracy.

Sino-Inst produces and supplies ultrasonic flow meters mainly for measuring water, seawater, industrial sewage, acid and alkaline liquids, alcohol, beer, various oils, and other single homogeneous liquids that can conduct ultrasonic waves. Of course, there are also ultrasonic flowmeters that can measure gas.

According to the measurement method can be divided into Doppler ultrasonic flowmeter, time difference ultrasonic flowmeter, hybrid ultrasonic flowmeter.

A）Doppler type ultrasonic flowmeter

B) time difference ultrasonic flowmeter

C）Mixed ultrasonic flowmeter

Related products:

Find more Ultrasonic Flow Meters for Liquids|Clamp-on|Insertion|inline

Sino-Inst, Manufacturer for Ultrasonic flow detectors. It can measure a single sound-conducting liquid medium of DN 15—150mm. It can measure even liquids such as water, seawater, oil, and slurry.

Sino-Inst’s Ultrasonic flow detectors, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.

Irrigation Flow Meters for Agriculture Water System

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What is an irrigation flow meter?

The irrigation flow meter is a flow meter designed for agricultural irrigation water counting. Agriculture, horticulture, etc. require water for irrigation. And water is becoming more and more expensive. The installation of flow measurement devices allows for effective monitoring and management of agriculture water systems.
The old mechanical water meters and today’s ultrasonic flow meters and electromagnetic flowmeters are widely used.

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Agricultural irrigation water system

It consists of irrigation canal head project, water transmission and distribution project and field irrigation project.

①Irrigation canal head project has reservoirs, pumping stations, dammed diversion projects, damless diversion projects, wells and other forms. Used to draw irrigation water at the right time and in the right amount.

② water transmission, water distribution projects include channels and canal buildings. Its task is to safely transport and reasonably distribute the water introduced at the head of the canal to all parts of the irrigation area. According to its function and scale, the general fixed channel is divided into dry, branch, bucket, agricultural four levels. Depending on the size of the irrigation area and the terrain, the number of levels of channels can be increased or decreased appropriately. Drainage buildings include diversion buildings, water measuring buildings, restraint buildings, articulation buildings, cross buildings, flood drainage buildings, drainage buildings, etc.

③ Field irrigation project refers to the temporary furrows, water transmission monopoly ditches and field irrigation ditches below the agricultural canals, border fields, and temporary water distribution and water measurement buildings. Used to irrigate the farmland. To meet the needs of normal crop growth or soil improvement.

Extended reading: Industrial VS Residential inline water flow meters

Irrigation flow meters for sale

Magnetic Water Flow Meter
Remote Magnetic Sewage Flow Meter
Insertion Magnetic Flow Meter
Handheld Ultrasonic Flow Meter
Ultrasonic Clamp on Flow Meter
Dual Channel Ultrasonic Water Meter

A magnetic Flow Meter is a flow meter that measures the flow of conductive fluids. Abbreviated as EMF, also called Electromagnetic flowmeters. It is a kind of Volumetric flow meter. A magnetic flow meter measures the velocity of conductive liquids moving through a pipe or conduit. In the wastewater treatment industry, a Magnetic Flow Meter is the best flow meter choice.

Read more about Everything You Need To Know About Electronic Flow Meters

The ultrasonic flow meter measures the liquid flow rate quickly and effectively. There are two types of ultrasonic flowmeter technology: Doppler frequency shift and transit time.

Transit time ultrasonic flow meter is most suitable for measuring the flow of cleaning liquid. Therefore, it is the most popular type of ultrasonic meter.

Doppler ultrasonic flow meter can measure the frequency difference of sound waves reflected from bubbles or particles in the airflow. It is suitable for aerated or dirty liquids.

Insertion Ultrasonic Water Flow Meter-Old Style
Insertion Ultrasonic Water Flow Meter-New Style

Card-type water meter with fixed control function, according to the local climate conditions, crops or green plants growth habits, program control can set up to five timed water supply time per day, in order to achieve water-saving irrigation, scientific irrigation.

The open channel flowmeter uses an ultrasonic sensor with a Parshall groove to measure open channel flow. Ultrasonic open channel flow meter is composed of 3 parts: level sensor, water measuring sink, and flow totalizer.

Ultrasonic open channel flowmeters are used to measure the flow of fluids in non-full tubular open channels and natural flowing water surfaces. It is called open channel flow detection. The measuring flume that is not full is called an open channel. The open channel flowmeter measures the water level in the measuring weir trough and then calculates the flow rate according to the water level flow relationship of the corresponding measuring weir trough.

Extended Reading: Chilled Water Flow Meter

Radar flow meter is a fully automatic flow meter based on microwave technology. It adopts advanced K-band plane radar technology. Through non-contact way to measure the flow rate and water level of the water body. According to the built-in software algorithm, it calculates and outputs the real-time section flow and accumulated flow.

The radar flow meter can be used for non-contact flow measurement in rivers, irrigation channels, underground drainage networks, flood control, and early warning. The product features low power consumption, compact size, high reliability, and easy maintenance. The measurement process is not affected by temperature, sediment, river pollutants, floating objects on the water surface, and other factors.

Extended Reading: Collection of Industrial Insertion Flowmeter Type

Extended reading: 2 inch Water Flow Meter

river flow measurement instruments

The methods of river flow measurement are as follows:

1.Flowmeter method
The flow of the river is measured directly using a flow meter.
There are many types of flowmeters, mainly including differential pressure, electromagnetic, trough and weir flowmeters.
It can be selected and used according to the flow range of the actual flow and the test accuracy requirements.

2.Volume method
Pour river water into a container of known capacity and measure the time it takes to fill the container. Repeat the measurement several times. A method of calculating the amount of water by finding its average value t(s).
The method is simple and easy to implement and has high measurement accuracy. Suitable for rivers with small river flow.
However, there should be an appropriate drop between the overflow port and the receiving water body, or an aqueduct can be used to form an error.

3.Buoy method
Select a straight river reach, and measure the cross-sectional area of ​​the water flow within a 2m interval of the river reach. Find the area of ​​its average cross-section.
Drop buoys in the upper reaches of the river and measure the time it takes for the buoys to flow through the identified reaches (L).
Repeat the measurement several times to obtain the average value (t) of the required time.
The flow rate (L/t) can be calculated.
The flow can then be calculated as follows:

Q=60V*S

where Q is the water flow, and the unit is m^3/min.
v is the average velocity of water flow, and its value is generally 0.7L/t, m/s.
S is the average cross-sectional area of ​​water flow, in m^2.

4.Flow meter method
By measuring the cross-sectional area of ​​the water flow, the river flow rate is measured with a current meter to calculate the river flow.
When measuring, the number of vertical measuring points and the number of horizontal measuring points need to be determined according to the depth and width of the channel.
This method is simple, but it is easily affected by water quality, and it is difficult to achieve continuous determination.

5.Acoustic Doppler flow velocity measurement
Acoustic Doppler flow velocity measurement is developed using the principle of acoustic Doppler. It can simultaneously measure the cross-sectional shape, water depth, flow velocity and flow rate of the river bed at one time, and is suitable for flow monitoring of large rivers.

The flowmeter’s host and transducer are housed in a waterproof container. All immersed in water when working. It is connected with a portable computer through a waterproof cable, and the operation and control of the flowmeter are carried out on the portable computer.
From the initial blind zone of more than 1m, it has been reduced to the so-called “zero blind zone”. The section unit is reduced to the current 0.05~0.25m. Make it possible to apply it on wide and shallow rivers.

Read more about: Common River Water Level Measurement Methods

Battery operated electromagnetic flow meter-GRPS-new irrigation water flow meter

GPRS wireless remote electromagnetic flowmeter inherits the advantages and functions of the original electromagnetic flowmeter and supports GPRS wireless communication.

Only a mobile phone card with GPRS wireless Internet access function is required, and you can easily log in to the Internet and establish a connection with a remote computer without connecting other module devices. Support Kingview.

The battery-powered converter comes standard with a regular lithium battery pack that lasts 3–6 years. If equipped with a high-capacity lithium battery pack, the continuous working time will be longer.

It can easily realize remote monitoring of the electromagnetic flowmeter’s instantaneous flow, instantaneous flow rate, flow percentage, fluid conductance ratio, forward cumulative value, reverse cumulative value, alarm status and other data. With disconnection automatic connection function, support dynamic IP address.

This Battery operated electromagnetic flow meter has become the choice of many users.

How to Select the Right Agriculture Flow Meter

Due to the modernization of agriculture and the realization of precision agriculture, flowmeters are bound to play an increasingly important role in farmland irrigation.
Therefore, on the basis of a comprehensive comparison of the measurement methods and characteristics of various flowmeters on the market. You should choose flow meter products that are more in line with the requirements of farmland water conservancy irrigation, safe, reliable, economical and durable.

The principle of choosing a flowmeter is to have a deep understanding of the structural principles and fluid characteristics of various flowmeters. At the same time, the selection should be made according to the specific situation of the site and the surrounding environmental conditions. Economic factors must also be taken into account.

In general, you should choose from the following five aspects:

① Performance requirements of the flowmeter;

  • Whether to measure flow (instantaneous flow) or total amount (cumulative flow);
  • Accuracy requirements;
  • Repeatability;
  • Linearity;
  • Flow range and range;
  • Pressure loss;
  • Output signal characteristics and flowmeter response time, etc.

② fluid characteristics;

  • Fluid temperature and pressure
  • fluid density
  • Viscosity
  • Chemical corrosion and scaling
  • compression factor

③ Installation requirements;

  • Field piping wiring
  • The flow direction of the fluid
  • The upstream and downstream straight pipe sections of the flowmeter
  • Pipe diameter and pipe vibration
  • The installation position of the valve
  • Protective accessories
  • Electrical connection and electromagnetic interference
  • Pulsating flow and unsteady flow

④ Environmental conditions;

  • Ambient temperature
  • Ambient humidity
  • Security
  • Electrical interference

⑤ The price of the flow meter.

  • Installation fee
  • Running cost
  • Testing fee
  • Maintenance costs and spare parts costs, etc.

Frequently
Asked
Questions

Help Center

In theory, there are many ways to measure irrigation flow.
However, from a practical application point of view I will tell you:

If it is a closed pipe, use a flowmeter. Electromagnetic flowmeters or ultrasonic flowmeters are both good choices.
If it is an open channel, then an open channel flow meter is used.

If you want to divide the flow meter into three categories. I think it can be divided into volumetric flowmeters, mass flowmeters, and velocity flowmeters.

If you choose a water meter. Then the diameter of the water meter is determined according to the rated flow of the water meter and the user’s water consumption and water use method.

If you choose a flow meter. It is necessary to combine the selection reference parameters mentioned above.

The general measurement is to use an electromagnetic flowmeter.

Magnetic flowmeters use the principle of Faraday’s Law of Electromagnetic Induction to measure the flow rate of liquid in a pipe. In the magnetic flowmeter pipe parts, a magnetic field is generated and channeled into the liquid flowing through the pipe.

As fluid flows through the magnetic field, conductive particles in the fluid create changes. This variation is used to measure and calculate the velocity of water flow through the pipe. When the fluid moves faster, more voltage is generated. The electronic transmitter processes the voltage signal to determine the liquid flow.

Read more about Digital Water Flow Meters

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Sino-Inst is Manufacturer of Irrigation Flow Meters. We supply more than 20 kinds of Irrigation Flow Meters. 60% magnetic flow meter, 20% ultrasonic flowmeters, and other types of flowmeters.

Irrigation Flow Meters are mainly used for flow measurement of Agriculture Water System.
It can measure even liquids such as water, seawater, oil, and slurry.

Irrigation Flow Meters enable stable water measurement and control. This greatly meets the measurement needs of many Farm and irrigation industry applications. Can be used from small to large tubes.

Sino-Inst’s Irrigation Flow Meters, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.

The entire team at Sino-Inst’s has received excellent training, so we can ensure that every client’s needs are met. For assistance with your product requirements, whether it’s a Irrigation Flow Meters, level sensor, or other device, give us a call.

Static Pressure vs Dynamic Pressure vs Total Pressure

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You may have heard of Static Pressure, Dynamic Pressure and Total Pressure. Especially in some industrial process pipe parameters. So what are Static Pressure, Dynamic Pressure and Total Pressure? What is the difference between them? How are they measured? Let’s take a look together.

RFQ Pressure Transmitters

Static pressure vs dynamic pressure vs total pressure

According to the knowledge of fluid mechanics. The vertical force acting on the unit area of the fluid is called pressure. When the air flows along the inner wall of the duct, its pressure can be divided into static pressure, dynamic pressure and full pressure. The unit is mmHg or kg/㎡ or Pa, respectively.

Static pressure (Pi).

What is static pressure?

Static pressure is the pressure generated by the air molecules hitting the duct wall due to irregular movement.
When calculating, the static pressure with absolute vacuum as the calculation zero points are called absolute static pressure.
The static pressure with atmospheric pressure as the zero point is called relative static pressure.
The static pressure of air in air conditioning refers to the relative static pressure.
The static pressure is positive when it is higher than atmospheric pressure, and negative when it is lower than atmospheric pressure.

Dynamic pressure (Pb).

What is dynamic pressure?

Dynamic pressure refers to the pressure generated by the flow of air, as long as the air flow in the duct has a certain dynamic pressure, and is positive. Dynamic pressure = 0.5 * air density * wind speed 2 .

Total pressure (Pq).

What is total pressure?

The total pressure is the algebraic sum of the static and dynamic pressures: Pq=Pi+Pb .

The total pressure represents the total energy of 1m3 of gas. If the atmospheric pressure is the starting point of the calculation, it can be positive or negative.

Extended reading: Pressure indicator transmitters

Extended reading: Pressure Sensor Applications-Featured Industry Applications

The difference between static pressure, dynamic pressure and total pressure

Different nature

  1. Total pressure: The pressure measured parallel to the wind flow, directly opposite to the direction of the wind flow.
  2. Static pressure: the pressure on the surface of an object at rest or in uniform linear motion.
  3. Dynamic pressure: When the object is moving in the fluid, the surface in the direction of the fluid movement. The fluid is completely blocked, where the fluid velocity is 0. Its kinetic energy is transformed into pressure energy, and the pressure increases.

Extended reading: wireless pressure transmitter

Features are different

1.Total pressure: air conditioning units or fresh air units are often installed at the end of the fan, the fan outlet wind speed is high, high dynamic pressure, static pressure is small. Engineering often installed at the exit of the anechoic static pressure box, reduce the dynamic pressure, increase the static pressure. At the same time, the same flow, muffling effect.

2.Static pressure: with no noise, no vibration, no impact.

3.Dynamic pressure: only the directional flow of air to show dynamic pressure. Dynamic pressure is directional, only the plane perpendicular or oblique to the direction of wind flow pressure. The plane of the vertical flow direction to bear the maximum dynamic pressure, the plane of the parallel flow direction to bear the dynamic pressure is zero. In the same flow section, because the wind speed at each point is not equal, the dynamic pressure varies. Dynamic pressure is not absolute pressure and relative pressure, always greater than zero.

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Different applications

  • Total pressure: applied to air conditioning or fan products.
  • Static pressure: applied to fluid dynamics.
  • Dynamic pressure: applied to mines, aerospace, etc.

Extended Reading: Up to 800°C High Temperature Pressure Sensor

What is an example of static and dynamic pressure?

Example of static pressure: When water is stored in a closed container, the pressure generated by the water in the container is static pressure. For example, water stored in a water tower develops pressure due to its height.

Example of dynamic pressure: When water flows in a pipe, in addition to the static pressure due to the weight of the water, there is also pressure due to the flow speed of the water. This part of the pressure is dynamic pressure. For example, the pressure created when water from a faucet hits the bottom of a wash basin.

Dynamic Pressure Calculator

Dynamic pressure is the kinetic energy of a flowing fluid – liquid or gas – per unit volume – and can be expressed as

pd = 1/2 ρ v²

Where:
pd = dynamic pressure (N/m2 (Pa), lbf/ft2 (psf))
ρ = density of fluid (kg/m3, slugs/ft3)
v = velocity (m/s, ft/s)

Online Dynamic Pressure Calculator

What is a dynamic pressure sensor?

The piezoelectric effect is the main operating principle of dynamic pressure sensors. Dynamic pressure sensors cannot be used for static measurements.

This is because the charge after an external force is only saved when the circuit has an infinite input impedance.

This is not the case in practice, so this determines that dynamic pressure sensors can only measure dynamic stresses.

Extended Reading: Electronic Pressure Switch for Air Compressor

Featured Static Pressure & Dynamic Pressure Sensors

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Extended reading: Measuring Flow With Pressure Sensors

Static pressure sensor and dynamic pressure sensor difference

  1. Diaphragm pressure sensor is according to the structure of the sensor, according to the sensing principle diaphragm pressure sensor can be divided into different types such as piezoresistive, strain gauge, inductive, capacitive, piezoelectric, etc.
  2. Among the above different principles of pressure sensors, piezoelectric pressure sensors are only suitable for measuring dynamic pressure. Therefore, dynamic calibration is required; other dynamic and static pressures can be measured. The most applications belong to the quasi-static measurement of very low frequency. Therefore, static calibration is the most used form of calibration. When the measured pressure band is wide, all kinds of pressure sensors should do frequency response calibration.

Extended reading: Silicon Pressure Sensor

Applications of dynamic pressure sensors

Dynamic pressure sensors are mainly used in the measurement of acceleration, pressure and force.

Dynamic pressure sensors are also widely used in biomedical measurements. For example, ventricular catheter microphones are made of piezoelectric sensors. Because dynamic pressure measurements are so common. This is why dynamic pressure sensors are so widely used.

Dynamic pressure transducers are used in a wide range of applications, typically to measure speed, pressure, and force. Therefore, they have a very high value in some products.

Extended reading: Best Price Ceramic Pressure Sensor

Frequently
Asked
Questions

Help Center

The static pressure sensor is based on atmospheric pressure or absolute vacuum, and compares the difference between the measured pressure and atmospheric pressure or absolute vacuum.

A static pressure sensor can be thought of as a specific form of differential pressure sensor. However, due to the measurement requirements, there will be large differences in the structure of the two.

In ventilation systems, static pressure is the pressure exerted by the air inside a building relative to the outside air pressure when the exhaust fan is turned on. Measuring and maintaining proper negative pressure allows ventilation systems to mix outside and inside air more efficiently.

Extended reading: Industrial Pressure Transmitters|Buy from the manufacturer

Dynamic pressure, when an object moves in a fluid, on the surface facing the direction of fluid motion, the fluid is completely blocked. The fluid velocity here is 0. Its kinetic energy is converted into pressure energy. The pressure increases. Its pressure is called total resistance pressure . Abbreviated as total pressure or total pressure, represented by P. The difference between it and the pressure at the undisturbed place (ie static pressure, represented by P static) is called dynamic pressure (represented by P dynamic)

Extended reading: Featured Diaphragm Seal Pressure Transmitters

The duct static pressure sensor is a detection instrument that mainly detects the difference of wind pressure on both sides of the filter. Real-time data monitoring and measurement of gas positive pressure, negative pressure and differential pressure can be realized through the wind pressure sensor. Equipped with a pitot tube pressure device, it can realize the three-in-one detection of wind pressure, wind speed and air volume.

Extended reading: how to calibrate a pressure transmitter

Diaphragm pressure sensors are based on the structure of the sensor. According to the sensing principle, diaphragm pressure sensors can be divided into different types such as piezoresistive, strain gauge, inductive, capacitive, and piezoelectric.

Among the above-mentioned pressure sensors with different principles, piezoelectric pressure sensors are only suitable for measuring dynamic pressure. Therefore, dynamic calibration is required;

Other dynamic and static pressures can be measured, and the most widely used is the quasi-static measurement with a very low frequency. Therefore, static calibration is the most widely used calibration form. When the measured pressure frequency band is wide, all kinds of pressure sensors should be calibrated for frequency response.

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The influence of Reynolds number on the accuracy of the flow meter

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What is Reynolds number?

Reynolds number is a dimensionless number that can be used to characterize the flow of a fluid. The ratio of the inertial force Fg and viscous force (internal friction) Fm during fluid flow is called Reynolds number. It is expressed by the symbol Re. Re is a factorless quantity. The Reynolds number can be used to distinguish the flow of fluid is laminar or turbulent. It can also be used to determine the resistance to the flow of an object in a fluid.

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Instrument constant of flow meters, i.e. Reynolds number

Reynolds number is an infinite parameter used as a criterion to determine the flow pattern of a fluid as it flows through a pipe. It is related to pipe diameter, flow rate, and medium viscosity.

The first used to determine the flow pattern of the fluid is turbulent flow through laminar flow. A side Re greater than 3200 or more can be judged as turbulent flow. Of course, from the laminar flow to the turbulent flow of the Reynolds number has a transition. So be specific and say that the Reynolds number must be greater than a certain value to say is to restore turbulent flow. Less than a certain value is said to be restored laminar flow.

Re = ρvd/μ, where v, ρ, μ are the fluid velocity, density and viscosity coefficient, d is a characteristic length. For example, if fluid flows through a circular pipe, d is the equivalent diameter of the pipe.

When measuring the flow rate of a fluid in a pipe, it is often necessary to understand its flow state, velocity distribution, etc. Reynolds number is to characterize the fluid flow characteristics of an important parameter.

Fluid flow inertia force Fg and viscous force (internal friction) Fm ratio called Reynolds number. Re is a factor less quantity.

The Reynolds number is small, which means that the fluid flow between the viscous force between the masses dominates, the fluid masses parallel to the inner wall of the pipe flow regularly, laminar flow state.

Reynolds number is large, which means that the inertia force dominates, the fluid is the turbulent flow state, general pipe Reynolds number Re < 2000 for laminar flow state, Re> 4000 for turbulent flow state, Re = 2000 ~ 4000 for the transition state.

In different flow states, the law of motion of the fluid. The distribution of velocity is different, so the average velocity of the fluid in the pipeline υ and the maximum velocity υmax ratio is also different. Therefore, the size of the Reynolds number determines the flow characteristics of viscous fluids.

When the external conditions are geometrically similar (geometrically similar pipes, fluid flowing through geometrically similar objects, etc.), if their Reynolds numbers are equal, the fluid flow state is also geometrically similar (hydrodynamically similar). This law of similarity is the basis for the standardization of flow measurement throttling devices.

Extended Reading: Sanitary Flow Meters-316SS,Tri clamp-Pulse- for Brewery

The influence of Reynolds number on the vortex flowmeter

The influence of Reynolds number on the vortex flowmeter in a certain range of Reynolds number. Vortex flowmeter output frequency signal with the volume of flow through the measuring tube between the relationship is not affected by the fluid properties (density, viscosity) and components. That is, the flow coefficient is only related to the vortex generator and the shape and size of the pipe.

Therefore, only in a typical medium in the calibration of its flow coefficient and applicable to a variety of media. This is a major advantage of the vortex flowmeter.

However, if the Reynolds number exceeds this range, it will have an impact.

Extended reading: Fluid flow meter types

Vortex flowmeter working principle

In the fluid flow in the pipeline set a vortex generator (resistance fluid). So in the volume downstream of the generator will alternately produce a regular vortex. This vortex is called Kaman vortex street.

The vortex generator is the main component of the detector. It is closely related to the flow characteristics (meter coefficient, linearity, range, etc.) and resistance characteristics (pressure loss) of the meter, and the requirements for it are as follows.

A vortex flowmeter can control the vortex in the direction of the axis of the vortex generator synchronous separation.
In a wide range of Reynolds numbers, there is a stable vortex separation point, maintaining a constant Strohal number.
The ability to produce a strong vortex street with a high signal-to-noise ratio of the signal.
Simple shape and structure, easy processing and standardization of geometric parameters, as well as installation and combination of various detection elements.
materials should meet the requirements of fluid properties, corrosion resistance, abrasion resistance, and resistance to temperature changes.
The inherent frequency is outside the frequency band of the vortex street signal.

Due to strict environmental requirements, some process industries, especially chemical, paper, and water treatment, are all placed under the strict monitoring of the agency. This will drive the vortex flowmeter production increase.

In addition, the privatization of municipal water treatment has become the trend, which will generate new investment to update the aging water treatment and sewer systems.

Multi-variable vortex flowmeters, which can measure temperature and pressure in addition to flow, are also in commercial use. Although its output is negligible, growth can be expected throughout the forecast period.

This enhanced measurement capability allows users to purchase fewer meters, requiring fewer process measurement points and thus fewer potential leak paths.

Read more about: How Vortex Flow Meter measure efficiently? For steam, gas, liquid 

Read more about: Coriolis Mass Flowmeter Working Principle

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Sino-Inst, Manufacturer for Vortex Flow Meters, like gas vortex flow meter, liquid vortex flow meter, sanitary vortex flow meter, insertion vortex flow meter, steam vortex flow meter, and natural gas vortex flow meter.

Sino-Inst’s vortex Flow Meters, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.

Technical Guide – Thermal mass flow meter

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What is a Thermal Mass Flow Meter ?

The thermal mass flow meter is also called Thermal mass flow sensors, or thermal gas flow meters. The thermal mass flow meter is a meter that uses the principle of heat transfer to detect flow.

That is, the measurement is performed based on the heat exchange relationship between the flowing fluid and the heat source (the object heated outside the fluid or the heating body outside the measuring tube).

The main measurement gas. Thermal gas mass flow meters are mainly divided into two categories, namely: thermally distributed and immersed (or plug-in).

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Thermal mass flow meter working principle

Thermal gas mass flow meter is designed on the basis of thermal dispersion. And adopts method of constant differential temperature to measuring gas flow. It has advantages of small size, easy installation, high reliability and high accuracy, etc.

The meter contains two platinum resistance temperature sensors. The thermal principle operates by monitoring the cooling effect of a gas stream as it passes over a heated sensor. Gas flowing through the sensing section passes over two sensors. One of which is used conventionally as a temperature sensor, whilst the other is used as a heater. The temperature sensor monitors the actual process values whilst the heater is maintained at a constant differential temperature above this by varying the power consumed by the sensor. The greater the gas velocity, the greater the cooling effect and power required to maintain the differential temperature. The measured heater power is therefore a measure of the gas mass flow rate.

The format of gas velocity and power is shown as below:

Where:

  • ρg is the specific gravity of the medium
  • V is velocity
  • K is the balance coefficient
  • Q is heater power
  • Δ T is a differential temperature
  • The medium temperature range of the meter is -40℃～220℃.

In the format (1), the specific gravity of medium is related to the density:

Where:

  • ρg is the medium density in working condition（kg/m3）
  • ρn is the medium density in standard condition, 101.325kPa, and 20℃ （kg/m3）
  • P is the pressure in working condition（kPa）
  • T is the temperature in working condition （℃）

In the formats (1) and (2), there is a certain functional relationship between the velocity and pressure in working condition, medium density, the temperature in working condition.

Due to the sensor temperature is always 30℃ higher than the medium temperature (environment temperature), and the meter adopts the method of constant differential temperature, therefore the meter do not need to do temperature and pressure compensation in principle.

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Know more about How Thermal Mass Flow Meter Technology Works?

Video source: https://www.youtube.com/watch?v=YfQSf2NBGqc

Thermal mass flow meter applications

The thermal measuring principle is widespread in the industry, and is being used successfully in many applications with gas flow, for example:

  • Oxygen, nitrogen, hydrogen, chlorine, and multi-component gas measurement.
  • Blast furnace gas and coke oven gas measurement.
  • Flue gas measurement.
  • Aeration and chlorine measurement in biogas and water treatment.
  • Compressed air measurement.
  • Gas flow measurement for natural gas, liquefied gas, flame gas, etc.
  • Primary air and secondary airflow measurement of power plant blast furnace
  • Flow measurement of underground ventilation or exhaust system

Further reading: Industrial LPG/Propane flow meter

Generally, Thermal mass flow meters produced in China are used to measure gas mass flow.

If you need to measure liquid mass flow. Please contact our sales engineer. We will provide you with detailed product recommendations.

Extended reading: Liquid Mass Flow Meter

Due to the continuous demand for energy due to the development of industrial automation. Natural gas as an energy source is used because of its green environmental protection and economic benefits. The metering of natural gas is very important.

The flow measurement of natural gas is divided into volume flow and mass flow. We mainly introduce the application of thermal gas mass flowmeter in natural measurement.

The main component of natural gas is methane, which contains relatively high molecular weight alkanes (mainly ethane. Natural gas is an explosive and flammable mixed gas. Some natural gas contains toxic sulfides, so the level of safety measurement requirements is high.

Natural gas is measured in the United States using normal cubic meters (corresponding to 101.325 kPa, zero degrees Celsius as the standard) standard cubic feet (corresponding to 14.73 psia, 60 degrees Fahrenheit as the standard.) Commercial natural gas has a combustion calorific value of approximately 10.8 kWh per normal state Cubic meters or 1000 BTU per standard cubic foot. Changes in its gas composition will cause changes in calorific value.

The requirements for the flowmeter thermal gas mass flowmeter during the measurement process:

  1. The mass flow can be measured directly without temperature and pressure compensation.
  2. Understanding the precise gas composition is the main parameter that determines the energy content.
  3. Maintain long-term measurement accuracy
  4. High-precision measurement can be restored by simply cleaning the probe
  5. Low flow rate, low flow rate, high sensitivity signal

Read more about: Natural Gas Flow Meter Selection Guide

Thermal mass flow meter advantages

  1. No need for temperature and pressure compensation for gas flow measurement. Convenient and accurate measurement;
  2. Wide range ratio, can be used for gas leak detection;
  3. Measuring flow rate range: 0.1Nm/s～100Nm/s.
  4. Good seismic performance and long service life, free from the influence of vibration on measurement accuracy;
  5. Overall digital circuit measurement, accurate measurement and convenient maintenance;
  6. Using RS-485 communication, factory automation and integration can be realized. click for inqueries
  7. No pressure loss, suitable for pipes of any shape with known cross-sectional area.
  8. Corrosion-resistant sensor, suitable for measuring corrosive gas.
  9. It is especially suitable for large-caliber measurement to ensure the accuracy of measurement and is suitable for trade settlement.
  10. The amount of construction is very small. Due to the plug-in structure, it can be installed and maintained online.
  11. The base-type instrument can display on-site and control with alarm.

Thermal mass flow meter disadvantages

  1. The thermal mass flow meter responds slowly.
  2. Places where the measured gas composition changes greatly. Due to changes in the cp value and thermal conductivity, the measured value will vary greatly and cause errors.
  3. For small flow, the meter will bring considerable heat to the gas to be measured. 　
  4. For thermally distributed thermal gas mass flow meters, if the measured gas deposits a scale layer on the pipe wall, the measured value will be affected. Must be cleaned regularly. The thin tube type instrument has the disadvantage of being easy to be blocked, and it cannot be used under normal circumstances.
  5. The use of pulsating flow will be restricted.
  6. Thermal mass flow meters for liquids are also restricted in the use of viscous liquids.

Read more about: Benefits Of Digital Gas Mass Flow Meters

Extended reading:
What is the K-factor in a flow meter?
Cryogenic Flow Meters|Liquid Nitrogen-Liquid Oxygen-LNG fluids

FAQ

Thermal mass flowmeters can be divided into contact and non-contact types according to different heat sources and temperature measurement methods.

1. Contact thermal mass flow meter

The heating element and temperature measuring element of this mass flowmeter are placed in the pipe of the fluid to be measured. In direct contact with the fluid, it is often called Thomas flowmeter. It is suitable for measuring the larger mass flow of gas. Due to heating and measuring elements Direct contact with the measured fluid, so the components are susceptible to fluid corrosion and wear. It affects the measurement sensitivity and service life of the instrument. It is not suitable for measuring high flow rate and corrosive fluid, which is the shortcoming of contact type.

2. Non-contact thermal mass flow meter

The heating and temperature measuring components of this flowmeter are all placed outside the fluid pipeline. They do not directly contact the measured fluid. Overcoming the shortcomings of contact.

Extended reading: Gas mass flow controller working principle

Mass flow rate refers to the flow rate of fluid quantity expressed by mass.
The mass flow rate can be expressed by the formula: qm=m/t=ρ×u×A.
In the formula, QM is the mass flow rate, kg/s.
m is the unit fluid mass, kg.
ρ is the fluid density, kg/m3.
t is the unit time, s.
u is the average flow velocity in the pipe, m/s.
A is the cross-sectional area of ​​the pipeline, m2.

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Read more about: Coriolis Mass Flowmeter Working Principle

Mass flow rate vs Volumetric flow rate is what we must use in flow measurement and control. In this post, we compare the concept of volume flow and mass flow and the conversion between the two.

Commonly used flow meters, such as orifice plates. Turbine flowmeter. Vortex flowmeter. Electromagnetic Flowmeter. Rotameter. The flow measurement value of ultrasonic flowmeter and oval gear flowmeter is the volume flow of fluid. Coriolis mass flow meters and thermal gas mass flow meters measure mass flow.

Read more about: New Guide: Mass Flow Rate vs Volumetric Flow Rate

The gas mass flow controller is based on the principle of thermal mass flow measurement. With control valve. The Micro Gas Flow Controller (MFC) is used to precisely measure and control the mass flow of gas.

Read more about: Gas mass flow controller working principle

Air mass flow meter VS Controller

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A wide variety of Thermal Mass Flow Meters options are available to you, such as free samples, paid samples. All of our flow meters can work with the AMS NEW TREX. About 13% of these are magnetic flow meter. 14% are Insertion Magnetic Flow Meter. 25% are Venturi flow meter. 13% are Handheld ultrasonic flow meter, and others are Liquid Turbine Flow Meters.

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You can ensure product safety by selecting from a certified supplier, with ISO9001, ISO14001 certification.

Beginner’s Guide: Variable Area flow meter

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What is a variable area flow meter?

Variable area flow meters are flow meters in which the fluid must pass through a restricted area. Because the flow cross-sectional area of ​​the flow meter varies with the height of the float. Therefore, this type of flowmeter is called variable area flowmeter or equal pressure drop flowmeter. The typical instrument of this type of flowmeter is a rotameter. This is in contrast to flow meters such as orifice plates and venturi tubes, where the area of ​​the flow element remains fixed. Variable area flowmeters can measure of gas and fluid flow.

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Variable area flow meter principle

The principle of the variable area flowmeter is to keep the pressure drop constant and use the change of the throttle area to measure the flow rate. It consists of a tapered tube gradually expanding from bottom to top and a rotor or float placed in the tapered tube.

When the fluid flows through the tapered tube, the float in the tube is pushed up to a height corresponding to the flow rate and floats.

When the flow rate increases, the impulse acting on the rotor increases. Because the weight of the rotor in the fluid is constant. The rotor rises. The corresponding annular gap between the rotor and the tapered tube is also increased. The flow rate of the fluid flowing through the annulus decreases. Impulse is also reduced. Bring the rotor to balance in the new position. According to the float position of the rotor, the instantaneous flow value can be measured.

The advantages of area flow meters are simple structure, easy testing, and suitable for measuring small flow rates.

Its disadvantage is that it is easily affected by factors such as fluid density, pressure and viscosity. When testing the flue gas flow, because the flue gas contains dust, the area flowmeter cannot be used.

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Extended reading: Gas Rotameter Tips

Variable area flow meter advantages and disadvantages

  • The advantages of the variable area flow meter are simple structure and easy testing, suitable for measuring small flow.
  • The disadvantage of variable area flow meter is that it is easily affected by factors such as fluid density, pressure, and viscosity. When testing the flue gas flow, because the flue gas contains dust, the area flowmeter cannot be used.

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Variable area flow meter types

We can classify according to different product materials. Including the following categories:

Plastic variable area flow meter

The main parts such as the liquid plastic tube rotameter cone tube are made of AS, ABS plastic. Has relatively good corrosion resistance. The product also has the characteristics of reasonable structure, small size, lightweight, and the tapered tube is not easily broken. The plastic tube rotor flowmeter can be widely used in chemical, environmental protection, food, and other industrial sectors.

Glass variable area flow meter

Glass rotor flowmeters are mainly used in various departments such as the chemical industry, petroleum, light industry, medicine, fertilizer, chemical fiber, food, dyes, environmental protection, and scientific research. Used to measure the flow of single-phase non-pulsating (liquid or gas) fluids. The anti-corrosion glass rotor flowmeter is mainly used for the detection of corrosive liquid and gas medium flow. Such as strong acid, strong acid, oxidant, strong oxidizing acid, organic solvent, and other corrosive gas or liquid medium flow detection.

Extended reading: Fluid flow meter types

Metal variable area flow meter

Metal float flowmeter is a kind of flow measuring instrument commonly used in industrial automation process control. It has the characteristics of small pressure loss, large detection range (range ratio 10:1), and convenient use. It can be used to measure the flow of liquid, gas, and steam, and is especially suitable for medium flow measurement with low flow velocity and small flow.

The metal float flowmeter has local display type and intelligent remote transmission type, with pointer display, instantaneous flow, cumulative flow, liquid crystal display, upper and lower limit alarm output, cumulative pulse output, standard two-wire 4-20mA current output, etc. form. Provide users with a very wide choice of space.

Read more about: What is a Flow Meter? Types and how does it work?

Variable area flow meter applications

Because Variable area flow meter has the advantages of simple mechanical structure, convenient processing, stable work, high reliability and low pressure loss. Especially it can measure the characteristics of low Reynolds book small flow medium. Therefore, it is widely used in gas and liquid flow measurement and automatic control systems.

  1. It is suitable for the measurement of small-caliber and low-velocity gas, liquid and steam flow.
  2. Affected by a certain viscosity, it is not suitable to measure high-viscosity media
  3. When the flow rate exceeds 100m3/h, the pressure loss is large.
    Mostly used for process control instruments, the best accuracy is 1%, generally 1.5%, and the range ratio is 10:1
  4. It is not suitable for measuring medium with large density change. It is not suitable to measure the flow of pulsating medium (such as metering pump outlet).

To put it bluntly, even under the conditions of small flow rate, small diameter, low flow rate, low viscosity medium, and no magnetic coupling influence, the variable area flow meter is the best to use.

In addition, the installation of a Variable area flow meter is also very particular. For flow accuracy requirements too high, it is not suitable to use this flow meter!

Read more General-purpose Flow Totalizer for Data collection and calculation

Extended reading: non contact flow meter

Horizontal variable area flow meter

There are two installation directions for variable area flow meter: horizontal installation and vertical installation.

Horizontal installation is divided into left in and out, right in and out.

Vertical installation is divided into top in and bottom out, bottom in and top out.

This one is installed horizontally to measure nitrogen. It is purely mechanical to display instantaneous flow rate.

Read More about: What is the difference between rotameter and flowmeter?

Metal tube variable area flow meter

The metal tube variable area flowmeter is our rotameter.

The LZ series Rotameter Flowmeter provided by Sino-Inst adopts a 304/316 stainless steel structure. It can be used to measure the flow of liquid, gas and steam. Especially suitable for low flow velocity and small flow. Flow measurement of high temperature, high pressure, strong corrosion, conductive or non-conductive media.

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Vortex Flowmeter VS Rotameter

Vortex flowmeter and rotameter are two different flowmeters. The working conditions and use environments measured by each flowmeter are different. Therefore, the two flowmeters have their own advantages and disadvantages.

Rotameter is also called metal tube rotameter, which uses variable area measurement principle. Suitable for measuring liquid, gas and other measuring media. Its body uses all-metal structure. There are indication type, remote transmission type and explosion-proof type. Rotameter has 4-20mA standard analog quantity signal output and on-site indication. Especially its body is pointer type. This big advantage can be measured even without power. Widely used in power generation, pharmaceuticals, water treatment, etc.

Extended Reading: What is difference between rotameter and flow meter

The vortex flowmeter has two measurement types: the basic type and the temperature and pressure compensation integrated type. The basic model only measures a single flow rate. The temperature and pressure compensation type is a flow type that can measure temperature and pressure at the same time. The vortex flowmeter also has many advantages. It has the advantages of small pressure loss, large measuring range, high precision, and because the vortex flowmeter has no moving parts. Therefore, maintenance and installation are very simple.

Extended reading: How does a rotameter work

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Sino-Inst offers over 5 Variable area flow meters, with the Best Price.

A wide variety of Variable area flowmeters options are available to you, such as free samples, paid samples.

Sino-Inst is Variable area flowmeter supplier, located in China.

Variable area flowmeters products are most popular in North America, Mid East, and Eastern Europe.

The United States, and India, which export 99%, 1%, and 1% of Variable area flowmeters respectively.

You can ensure product safety by selecting from a certified supplier, with ISO9001, ISO14001 certification.

Introduction to Piezoelectric Pressure Sensors

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What is a piezoelectric pressure sensor?

The piezoelectric pressure sensor is a sensor that uses the piezoelectric effect of piezoelectric materials to convert the measured pressure into an electrical signal. Use electrical components and other machinery to convert the pressure to be measured into electricity. Measuring precision instrument for related measurement work. Such as pressure transmitters and pressure sensors.

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More Pressure Sensors

Piezoelectric pressure sensor working principle

Piezoelectric pressure sensors are mainly based on the piezoelectric effect (Piezoelectric effect). Use electrical components and other machinery to convert the pressure to be measured into electricity. Then perform measurement precision instruments such as pressure transmitters and pressure sensors.

Piezoelectric sensors can not be used in static measurement. The reason is the electric charge after the action of external force. When the circuit has infinite input resistance, it can be preserved.

But this is not the case.

Therefore, piezoelectric sensors can only be used in dynamic measurements.

Extended reading: Featured Diaphragm Seal Pressure Transmitters

Its main piezoelectric materials are: dihydrogen phosphate, sodium potassium tartrate and quartz. The piezoelectric effect is found on quartz.

When the stress changes, the electric field changes very little, and some other piezoelectric crystals will replace quartz.

Potassium sodium tartrate, it has a large piezoelectric coefficient and piezoelectric sensitivity. However, it can only be used indoors where the humidity and temperature are relatively low.

Dihydrogen phosphate is a kind of artificial crystal. It can be used in high humidity and high temperature environment. Therefore, its application is very wide.

With the development of technology, the piezoelectric effect has also been applied to polycrystals. For example: piezoelectric ceramics, niobate magnesium acid piezoelectric ceramics, niobate series piezoelectric ceramics and barium titanate piezoelectric ceramics, etc. are included.

The sensors based on the piezoelectric effect are electromechanical conversion and self-generation sensors. Its sensitive components are made of piezoelectric materials.

When the piezoelectric material is subjected to an external force, an electric charge will be formed on its surface. The electric charge will be amplified by the charge amplifier, the measuring circuit and the impedance converted. It will be converted into an electrical output proportional to the external force received.

It is used to measure force and non-electrical physical quantities that can be converted into force. For example: acceleration and pressure.

It has many advantages: lighter weight, reliable work, simple structure, high signal-to-noise ratio, high sensitivity and signal bandwidth, etc.

But it also has some shortcomings: some voltage materials are protected from moisture. Therefore, a series of moisture-proof measures need to be taken. And the output current response is relatively poor. Then it is necessary to use a charge amplifier or a high input impedance circuit to make up for this shortcoming. Make the instrument work better.

Extended reading: Silicon Pressure Sensor

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Piezoelectric pressure sensor advantages and disadvantages

  1. The advantages are bandwidth, high sensitivity, high signal-to-noise ratio, simple structure, reliable work, and lightweight.
  2. The disadvantage is that some piezoelectric materials need moisture-proof measures. And the output DC response is poor. It is necessary to use a high input impedance circuit or a charge amplifier to overcome this defect.

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The working principle of 5 common pressure sensors

In addition to the Piezoelectric Pressure Sensors described in this article, there are many pressure transmitters and pressure sensors that can convert pressure into electrical signals.

So how do these pressure transmitters and pressure sensors convert pressure signals into electrical signals? What are the characteristics of different conversion methods?

Here, I have summarized the measurement principles of several common pressure sensors for everyone. hope that it can help us.

Piezoresistive pressure sensors are mainly based on the piezoresistive effect (Piezoresistive effect). The piezoresistive effect is used to describe the resistance change of a material under mechanical stress.

Unlike the piezoelectric effect described above, the piezoresistive effect only produces impedance changes, and does not generate electric charges.

Most metal materials and semiconductor materials have been found to have a piezoresistive effect. Among them, the piezoresistive effect in semiconductor materials is much greater than that in metals.

Extended reading: wireless pressure transmitter working principle

Because silicon is the mainstay of today’s integrated circuits. The application of piezoresistive elements made of silicon becomes very meaningful.

Piezoresistive pressure sensors are generally connected to Wheatstone bridges through lead wires.

Normally, the sensitive core has no applied pressure, and the bridge is in a balanced state (called zero position). When the sensor is pressed, the chip resistance changes, and the bridge will lose balance.

If a constant current or voltage power supply is added to the bridge. The bridge will output a voltage signal corresponding to the pressure. In this way, the resistance change of the sensor is converted into a pressure signal output by the electric bridge.

The bridge detects the change in resistance value, and after amplification, it undergoes voltage and current conversion. Converted into the corresponding current signal. The current signal is compensated by the nonlinear correction loop. That is, a standard output signal of 4-20mA with a linear corresponding relationship between the input voltage is produced.

In order to reduce the influence of temperature changes on the resistance of the core, and improve the measurement accuracy. The pressure sensor adopts temperature compensation measures to maintain a high level of technical indicators such as zero drift, sensitivity, linearity, and stability.

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The capacitive pressure sensor is a pressure sensor that uses capacitance as a sensitive element to convert the measured pressure into a change in capacitance value.

This kind of pressure sensor generally uses a circular metal film or a metal-plated film as an electrode of the capacitor. When the film deforms under pressure, the capacitance formed between the film and the fixed electrode changes.

The electrical signal that has a certain relationship with the voltage can be output through the measuring circuit.

The capacitive pressure sensor is a capacitive sensor with a variable pole pitch. It can be divided into a single capacitive pressure sensor and a differential capacitive pressure sensor.

Read more about Capacitive pressure transducer.

A variety of sensors that use electromagnetic principles are collectively referred to. They mainly include inductive pressure sensors, Hall pressure sensors, and eddy current pressure sensors.

Extended reading: how to calibrate a pressure transmitter

The working principle of inductive pressure sensors is due to the different magnetic materials and permeability.

When the pressure acts on the diaphragm, the size of the air gap changes, and the change of the air gap affects the change of the inductance of the coil. The processing circuit can convert the change of this inductance into the corresponding signal output. So as to achieve the purpose of measuring pressure.

This kind of pressure sensor can be divided into two types according to the change of the magnetic circuit: variable magnetic resistance and variable magnetic permeability. The advantages of inductive pressure sensors are high sensitivity and large measuring range. The disadvantage is that they cannot be used in high-frequency dynamic environments.

Hall pressure sensors are made based on the Hall effect of certain semiconductor materials.

The Hall effect refers to when a solid conductor is placed in a magnetic field and a current flows through it.

The charge carriers in the conductor are biased to one side by the Lorentz force. Then a voltage (Hall voltage) is generated. The electric field force caused by the voltage will balance the Lorentz force.

Through the polarity of the Hall voltage, it can be confirmed that the current inside the conductor is caused by the movement of negatively charged particles (free electrons).

Eddy current pressure sensor is a pressure sensor based on the eddy current effect.

The eddy current effect is caused by the intersection of a moving magnetic field and a metal conductor, or the intersection of a moving metal conductor and the magnetic field perpendicularly.

In short, it is caused by electromagnetic induction effects. This action creates a current circulating in the conductor.

Extended reading: What is a pressure sensor?

Vibrating wire pressure sensor is a frequency sensitive sensor.

This kind of frequency measurement has the desired high accuracy. Because time and frequency are physical parameters that can be accurately measured. And the frequency signal can ignore the influence of cable resistance, inductance, capacitance and other factors during the transmission process.

At the same time, the vibrating wire pressure sensor also has strong anti-interference ability, small zero drift, good temperature characteristics, simple structure, high resolution, stable performance. It is convenient for data transmission, processing and storage. It is easy to realize the digitalization of the instrument.

Therefore, vibrating wire pressure sensors can also be used as one of the development directions of sensing technology.

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Sino-Instrument is a globally recognized supplier and manufacturer of
Pressure Transducers, located in China.

The top supplying country is China (Mainland), which supply 100% of Pressure Transducers respectively.

Sino-Instrument sells through a mature distribution network that reaches all 50 states and 30 countries worldwide.

Pressure Transducers products are most popular in Domestic Market, Southeast Asia, and Mid East. 

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