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? Types, Principles & Selection Guide

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Updated: April 10, 2026

A pressure sensor converts mechanical pressure into an electrical signal. It is the sensing element inside every pressure transmitter, transducer, and switch used in industrial process control. The electrical output—typically a change in resistance, capacitance, or voltage—is proportional to the applied pressure. Pressure sensors measure gauge, absolute, differential, or vacuum pressure depending on the reference. This guide covers the main sensing technologies, how each works, key specifications, and how to select the right type for your application.

Contents

What Is a Pressure Sensor?

A pressure sensor is a device that detects pressure applied to its sensing element and outputs a corresponding electrical signal. The sensing element is usually a thin diaphragm—made of silicon, stainless steel, or ceramic—that deflects when pressure acts on it. That deflection changes a physical property (resistance, capacitance, charge, or frequency) which is measured by the sensor’s internal circuitry.

Pressure sensors are the core component in pressure transmitters and transducers. Without the sensor, there is no measurement. The transmitter adds signal conditioning, temperature compensation, and a standardized output (4-20mA, 0-10V, or digital protocol) on top of the raw sensor signal.

Typical accuracy ranges from ±0.5% to ±0.04% of full scale depending on the technology and price point. Operating temperatures range from -40°C to +125°C for standard silicon sensors, with special designs reaching 300°C or higher for high-temperature applications.

4 Types of Pressure Measurement

The “type” of pressure a sensor measures depends on what reference it uses:

TypeReferenceTypical Application
Gauge pressureLocal atmospheric pressureProcess piping, tank pressure, pump discharge
Absolute pressurePerfect vacuum (0 Pa)Barometric, altitude, vacuum systems
Differential pressureAnother pressure inputFilter monitoring, flow measurement, level in pressurized tanks
Vacuum / compoundAtmospheric (negative range)Vacuum pumps, HVAC, packaging machines

Gauge pressure is the most common in industrial applications. When an engineer says “the line pressure is 10 bar,” they almost always mean gauge pressure—10 bar above atmospheric. For more on how static and dynamic pressures interact, see our guide on static pressure vs dynamic pressure.

5 Pressure Sensing Technologies

1. Piezoresistive (Diffused Silicon)

Four resistors are diffused directly into a silicon diaphragm and connected in a Wheatstone bridge. When pressure deflects the diaphragm, the resistors change value due to the piezoresistive effect, producing a millivolt output proportional to pressure. This is the most widely used technology in industrial pressure sensors.

Advantages: low cost, high volume production (MEMS), good linearity, fast response. Limitations: temperature sensitivity requires active compensation; not suitable for highly corrosive media without isolation diaphragm. Standard accuracy: ±0.25–0.5% FS.

2. Capacitive

A metal or ceramic diaphragm forms one plate of a capacitor. A fixed plate sits behind it. Pressure deflects the diaphragm, changing the gap and therefore the capacitance. The electronics measure this capacitance change with high resolution.

Advantages: excellent long-term stability, low power consumption, high overpressure tolerance (up to 100x rated pressure), very low temperature drift. This is the technology used in premium transmitters like the Rosemount 3051 and Yokogawa EJA series. Standard accuracy: ±0.04–0.1% FS.

3. Strain Gauge (Bonded Foil)

Metal foil strain gauges are bonded to a metal diaphragm or beam. Pressure deflects the structure, straining the gauges and changing their resistance. The resistance change is measured with a Wheatstone bridge. This technology works well for high-pressure applications (up to 10,000 bar) because thick metal diaphragms can handle extreme pressures.

Advantages: wide pressure range, robust construction, works at high temperatures. Limitations: lower sensitivity than piezoresistive, requires careful bonding. Standard accuracy: ±0.1–0.25% FS. For details on how pressure transmitters use these sensors, see our guide on how pressure transmitters work.

4. Piezoelectric

Piezoelectric crystals (quartz, PZT) generate an electric charge when mechanically stressed. The charge is proportional to the applied pressure. Unlike the other technologies, piezoelectric sensors only measure dynamic (changing) pressure—they cannot hold a static reading because the charge leaks away.

Advantages: extremely fast response (microseconds), wide frequency bandwidth, no external power needed for the sensing element. Applications: engine combustion analysis, blast pressure measurement, acoustic sensors. Not used for steady-state process control.

5. Resonant (Vibrating Element)

A vibrating wire, beam, or cylinder changes its resonant frequency when stressed by pressure. The frequency shift is measured digitally with very high resolution. This technology offers the best long-term stability and accuracy of any pressure sensing method.

Advantages: frequency output is inherently digital and noise-immune, excellent stability (±0.01% per year), high accuracy (±0.01–0.04% FS). Limitations: expensive, slower response than piezoresistive. Used in fiscal metering, meteorological stations, and calibration reference instruments.

TechnologyAccuracyBest ForLimitation
Piezoresistive±0.25–0.5%General industrial, OEM, HVACTemperature drift
Capacitive±0.04–0.1%Process control, custody transferHigher cost
Strain gauge±0.1–0.25%High pressure, hydraulic systemsLower sensitivity
Piezoelectric±1%Dynamic pressure, combustionNo static measurement
Resonant±0.01–0.04%Fiscal metering, calibrationExpensive, slow response

Sensor vs. Transducer vs. Transmitter

These three terms are often used interchangeably, but they describe different levels of signal processing:

TermWhat It DoesOutput SignalTypical Use
Pressure sensorConverts pressure to a raw electrical changemV (millivolts), pC (picocoulombs)OEM integration, PCB-level
Pressure transducerSensor + basic signal conditioning0–5V, 0–10V, mV/VTest & measurement, lab instruments
Pressure transmitterSensor + full conditioning + standardized output4-20mA, HART, Profibus, ModbusIndustrial process control, DCS/PLC

In practice: a pressure sensor is the raw MEMS chip. A transducer packages it with amplification and outputs a voltage. A transmitter adds temperature compensation, linearization, and a 4-20mA or digital output that can travel hundreds of meters to a control room. When specifying equipment for industrial applications, you almost always want a transmitter. For wiring details, see our pressure transducer wiring guide.

Key Specifications to Consider

When selecting a pressure sensor, these are the specifications that matter most:

  • Pressure range: Select a range where your normal operating pressure falls at 60–75% of the sensor’s full scale. This gives headroom for pressure spikes without sacrificing resolution.
  • Accuracy: Expressed as % of full scale (FS) or % of reading. A ±0.1% FS sensor on a 0–100 bar range has ±0.1 bar error at any point. For custody transfer, look for ±0.04–0.075% FS.
  • Temperature range: Both operating temperature (media touching the sensor) and ambient temperature (electronics). Silicon sensors typically handle -40 to +85°C. High-temperature versions with oil-filled capillary or cooling fins reach 300°C+.
  • Output signal: 4-20mA is the industrial standard for analog. HART adds digital communication over the same wires. For digital-only, Profibus PA and Foundation Fieldbus are common.
  • Media compatibility: The wetted parts (diaphragm, O-ring, process connection) must be compatible with the process fluid. 316L stainless steel handles most applications. Hastelloy, Monel, or tantalum for aggressive chemicals.
  • Process connection: 1/4″ or 1/2″ NPT, G1/2, M20x1.5, or flange-mounted. Match the connection to your existing pipe fittings.
  • Overpressure rating: The maximum pressure the sensor can withstand without permanent damage. Capacitive sensors typically tolerate 100x overpressure; piezoresistive typically 2–3x.

Common Industrial Applications

Pressure sensors are used across every process industry. Here are the most common application categories:

  • Process control: Monitoring and controlling pressure in reactors, distillation columns, heat exchangers, and pipeline systems. The 4-20mA signal feeds directly into a DCS or PLC for closed-loop control.
  • Flow measurement: Differential pressure sensors across an orifice plate, venturi, or flow nozzle measure flow rate. This is still the most common industrial flow measurement method. For GPM-based flow measurement, see our guide on flow meters with GPM units.
  • Level measurement: A pressure sensor at the bottom of a tank measures hydrostatic head, which is proportional to liquid level. Works for open and pressurized tanks (using a differential pressure sensor for the latter).
  • Hydraulic and pneumatic systems: Monitoring pump discharge, accumulator charge, cylinder force, and system pressure in mobile equipment, presses, and injection molding machines.
  • HVAC and building automation: Duct static pressure, chilled water system pressure, filter differential pressure, and refrigerant pressure in chillers.
  • Safety systems: Pressure relief monitoring, burst disc detection, and SIL-rated pressure switches for emergency shutdown systems per IEC 61511.

Pressure Sensors from Sino-Inst

Sino-Inst manufactures over 20 types of pressure sensors and transmitters covering gauge, absolute, differential, and high-pressure applications. All units ship with factory calibration certificates.

Gauge Pressure Sensor

4-20mA | 0–600 bar | ±0.5% FS | 316L SS

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Differential Pressure Sensor

4-20mA/HART | 0–16 MPa | Flanged mount

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Pressure Transmitter (4-20mA)

4-20mA/HART | 0–100 MPa | ±0.1% FS

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FAQ

What is the difference between a pressure sensor and a pressure transmitter?

A pressure sensor is the raw sensing element that converts pressure into a small electrical change (millivolts). A pressure transmitter packages the sensor with signal conditioning, temperature compensation, and a standardized industrial output (4-20mA, HART, Modbus). For process control, you need a transmitter.

How long does a pressure sensor last?

In normal industrial service, a quality pressure sensor lasts 10–20 years. Silicon MEMS sensors have no moving parts and minimal wear. The main failure modes are diaphragm corrosion (wrong material selection), overpressure damage, and electronics degradation from temperature cycling. Regular calibration checks catch drift before it becomes a problem.

Which pressure sensor technology is most accurate?

Resonant (vibrating element) sensors achieve the best accuracy at ±0.01–0.04% FS, but they are expensive. Capacitive sensors offer ±0.04–0.1% FS at a more reasonable price and are the standard choice for high-accuracy process applications. For general industrial use, piezoresistive sensors at ±0.25–0.5% FS provide the best cost-performance ratio.

Can a pressure sensor measure vacuum?

Yes. Absolute pressure sensors measure from 0 Pa (vacuum) upward. Compound pressure sensors (also called vacuum/pressure sensors) measure both positive and negative gauge pressure in a single range, for example -1 to +10 bar. For deep vacuum applications below 1 mbar, specialized capacitance manometers or Pirani gauges are used.

How do I choose the right pressure range?

Select a sensor where your normal operating pressure is 60–75% of the rated full scale. This gives enough headroom for pressure spikes without sacrificing measurement resolution. For example, if your process runs at 8 bar with occasional surges to 12 bar, a 0–16 bar sensor is a good fit. Never operate a sensor continuously above 90% of its rated range.

What is the temperature effect on pressure sensor accuracy?

Temperature changes affect both the zero point and the span of a pressure sensor. This effect is specified as a temperature coefficient, typically in %FS per 10°C. A good industrial transmitter has a total temperature effect of less than ±0.15% FS over a 10–50°C range after compensation. If your process temperature varies widely, look for a sensor with active digital temperature compensation or use a remote diaphragm seal to keep the electronics at stable ambient temperature.

Looking for a pressure sensor or transmitter for your application? Sino-Inst offers gauge, absolute, differential, and high-pressure models with customizable ranges and outputs. Our engineers can help you select the right technology, material, and connection for your specific process conditions. Contact us for a technical consultation or quotation.

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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

More water flow measurement and control solutions

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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Updated Apr 9, 2026 — Reviewed by Sino-Inst Engineering Team

In fluid mechanics, pressure splits into three components: static pressure, dynamic pressure, and total pressure. These are not three separate forces — they are three ways of describing the energy state of a moving fluid. Bernoulli\’s principle ties them together in one equation. If you work with HVAC ducts, pipeline flow measurement, or aerospace systems, you deal with these three pressures every day. This guide covers definitions, formulas, how to measure each one, and which instruments to use.

Contents

What Is Static Pressure

Static pressure is the pressure exerted by a fluid when you ignore its motion. Think of it as the “stored energy” component. In a sealed tank with no flow, all pressure is static. In a moving pipe, static pressure acts perpendicular to the flow direction — it pushes equally on all sides of the pipe wall.

The formula is straightforward. For a fluid column:

Pstatic = ρ × g × h

Where ρ is fluid density (kg/m³), g is gravitational acceleration (9.81 m/s²), and h is the fluid column height (m). In a 10-meter water column, static pressure at the bottom is approximately 98.1 kPa (about 1 atm).

In HVAC systems, duct static pressure typically ranges from 0.5 to 2.0 inches of water column (125–500 Pa). Too high means restricted airflow. Too low means the fan cannot push air to remote zones. A pressure transmitter mounted on the duct wall with a perpendicular tap measures static pressure directly.

What Is Dynamic Pressure

Dynamic pressure represents the kinetic energy of a moving fluid per unit volume. It only exists when the fluid is in motion. Stop the flow, and dynamic pressure drops to zero.

The formula:

Pdynamic = ½ × ρ × v²

Where ρ is fluid density (kg/m³) and v is flow velocity (m/s). Note the squared relationship — doubling the velocity quadruples the dynamic pressure. This is why high-velocity flows create much larger forces than low-velocity ones.

Practical example: air at standard conditions (ρ = 1.225 kg/m³) moving at 20 m/s produces a dynamic pressure of about 245 Pa. At 40 m/s, it jumps to 980 Pa. This matters in wind tunnel testing and in sizing pressure sensors for industrial applications.

Dynamic pressure is always positive. It has direction — it acts along the flow axis. A pressure tap flush with the pipe wall does not sense dynamic pressure. You need a probe facing directly into the flow, like a pitot tube.

What Is Total Pressure (Bernoulli’s Equation)

Total pressure (also called stagnation pressure) is the sum of static and dynamic pressure. Bernoulli’s equation for incompressible flow along a streamline states:

Ptotal = Pstatic + ½ρv²

The total pressure remains constant along a streamline in ideal (inviscid, incompressible) flow. When fluid slows down, dynamic pressure converts to static pressure. When it speeds up, static converts to dynamic. The total stays the same.

This is the principle behind every pitot tube measurement. A pitot tube has two ports: one facing into the flow (measures total pressure) and one perpendicular to the flow (measures static pressure). The difference between them is dynamic pressure, from which you calculate velocity:

v = √(2 × (Ptotal – Pstatic) / ρ)

In real systems with friction and turbulence, total pressure decreases along the flow path. The relationship between flow rate and pressure becomes more complex, and you must account for pressure losses in pipe fittings, valves, and elbows.

Quick Comparison Table

PropertyStatic PressureDynamic PressureTotal Pressure
DefinitionPressure from random molecular motionPressure from bulk fluid velocitySum of static + dynamic
FormulaPs = ρgh (column) or measured directlyPd = ½ρv²Pt = Ps + ½ρv²
DirectionActs in all directions (isotropic)Acts along flow direction onlyMeasured facing into flow
At zero flowEquals total pressureZeroEquals static pressure
SignPositive or negative (vacuum)Always positivePositive or negative
MeasurementWall tap perpendicular to flowCalculated from total minus staticPitot tube facing into flow
UnitPa, psi, inH₂OPa, psi, inH₂OPa, psi, inH₂O

How to Measure Static, Dynamic, and Total Pressure

Static Pressure Measurement

Drill a small hole (typically 1–3 mm) perpendicular to the pipe wall. Connect a pressure transmitter or manometer. The tap must be flush with the inner wall — any burr or protrusion will cause measurement errors. In round ducts, place the tap at the 3 o’clock or 9 o’clock position to avoid effects from gravity (condensate) or buoyancy.

Total Pressure Measurement

Insert a pitot tube with its open end facing directly upstream. The stagnation point at the tube opening brings the fluid velocity to zero, converting all kinetic energy to pressure. This reading is total pressure. For accurate results, align the tube within ±5° of the flow direction.

Dynamic Pressure (Velocity Pressure)

Dynamic pressure is not measured directly. Instead, connect a differential pressure transmitter between the total pressure port and the static pressure port. The DP reading equals dynamic pressure. From this, calculate flow velocity using the formula above.

For HVAC duct traversals, averaging pitot tubes (like an Annubar) provide a more representative velocity reading across the duct cross-section. Single-point pitot readings can miss the velocity profile and understate or overstate average flow. Follow the log-linear or equal-area traverse method per ASHRAE standards for best accuracy.

Industrial Applications

HVAC systems: Static pressure monitoring at key duct locations ensures the air handling unit delivers correct airflow. Excessive static pressure indicates blocked filters or closed dampers. Building automation systems use duct static pressure sensors as feedback for variable-frequency drives on supply fans.

Pipeline flow measurement: Differential pressure flow meters (orifice plates, Venturi tubes, flow nozzles) work by creating a pressure drop. The upstream and downstream straight pipe requirements ensure a stable velocity profile for accurate DP readings. The measured DP relates to flow rate through a square-root relationship.

Aerospace: Aircraft airspeed indicators use pitot-static systems. The pitot port measures total pressure (ram air). The static port measures ambient static pressure. The difference gives dynamic pressure, which converts to indicated airspeed. At higher speeds (above Mach 0.3), compressibility effects require corrections beyond Bernoulli’s incompressible equation.

Clean rooms and labs: Differential static pressure between rooms ensures contamination control. Positive-pressure rooms prevent outside air from entering. Negative-pressure isolation rooms prevent pathogens from escaping. Monitoring requires sensitive low-range pressure transmitters with 0–250 Pa or 0–500 Pa ranges.

Sino-Inst manufactures pressure transmitters suitable for static, differential, and dynamic pressure measurement across industrial applications.

Gauge Pressure Transmitter

4-20mA / HART | 0–100 kPa to 0–60 MPa | ±0.075% FS

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Differential Pressure Transmitter

4-20mA / HART | 0–6 kPa to 0–10 MPa | ±0.075% FS

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SI-503K Gas Pressure Sensor

0–5 kPa to 0–200 kPa | 4-20mA | Air & gas applications

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Frequently Asked Questions

What is the difference between static and dynamic pressure?

Static pressure exists whether the fluid moves or not — it comes from the weight and random molecular motion of the fluid. Dynamic pressure only exists when the fluid is in motion and represents the kinetic energy of that motion. Static pressure acts in all directions; dynamic pressure acts along the flow direction only.

Can dynamic pressure be negative?

No. Dynamic pressure equals ½ρv², and both density (ρ) and velocity squared (v²) are always positive. Dynamic pressure is zero when there is no flow and positive for any nonzero velocity, regardless of flow direction.

How does a pitot tube measure total pressure?

A pitot tube has an open end facing directly into the flow. At this stagnation point, the fluid velocity drops to zero, and all kinetic energy converts to pressure energy. The pressure reading at this point equals the total pressure (static + dynamic). A second port perpendicular to flow measures static pressure. The difference is dynamic pressure.

What is stagnation pressure?

Stagnation pressure is another name for total pressure. It is the pressure at a point where the fluid velocity has been brought to zero isentropically (without heat transfer or friction losses). In practice, the tip of a pitot tube approximates a stagnation point.

What instrument measures static pressure in HVAC ducts?

A duct static pressure sensor or low-range differential pressure transmitter connected to a wall tap. The tap should be drilled perpendicular to the duct wall, with no burrs. Common sensing ranges are 0–250 Pa, 0–500 Pa, or 0–1000 Pa depending on the system. The sensor’s reference port is left open to atmosphere or connected to a clean reference point.

Does Bernoulli’s equation apply to compressible flow?

The standard Bernoulli equation (Ptotal = Pstatic + ½ρv²) applies only to incompressible, inviscid, steady flow along a streamline. For compressible flow (gas at Mach > 0.3), you need the compressible form that accounts for density changes. For most industrial piping and HVAC applications, the incompressible form is accurate enough because flow velocities are well below Mach 0.3.

Need help selecting the right pressure instrument for your static, dynamic, or differential pressure measurement? Our engineering team can recommend the best sensor type, range, and output for your application.

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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

Related Products:

Extended reading: Ultrasonic Insertion Flow Meter for Lined/Large Pipes

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.

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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.

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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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Sino-Inst offer over 10 Thermal Mass Flow Meters, with Best Price.

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.

Sino-Inst is Thermal Mass Flow Meter suppliers, located in China. Mass flow meter products are most popular in North America, Mid East, and Eastern Europe.

The United States, and India, which export 99%, 1%, and 1% of Thermal Mass Flow Meter respectively.

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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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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. 

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