Professional Partner for Measure &amp; Control

Measuring oil flow is to measure the volume or mass flow of oil. According to the actual demand, and the actual parameters of the oil, the appropriate oil flow meter can be selected.

Extended reading: What Is Hydraulic Flow Meter?

Industrial oil flow meters measure the volume or mass of oil. Can realize the mutual conversion of volume and mass.

The main industrial oils are hydraulic oil. Gear Oil. Turbine oil. Compressor oil. Refrigeration oil. Transformer oil. Cylinder oil, heat treatment oil, heat transfer oil, etc. Of course, edible oil can also be produced in the industry. In addition, there are greases with lubricating oil as base oil and thickening agent.

Therefore, whether it is a company that uses, trades, or produces oil, it needs to accurately measure the oil flow.

There are many common oil flow meters, such as turbine flow meters, positive displacement flow meters, gear flow meters, mass flow meters, etc.

In the oil and gas industry, monitoring is required most of the time during transportation and processing. Including pressure, temperature, liquid level, flow, viscosity and more. And to achieve these functions are process meters.

Therefore, in the oil and gas industry, many meters are used. For example: thermometers, pressure gauges, flow meters, etc.

If the flowmeter is divided into 5 categories. Then the five commonly used flowmeters are:

Electromagnetic flowmeter
Differential pressure flowmeter
Turbine flowmeter
Ultrasonic flowmeter
Volumetric flowmeter (PD)

Different digital flow sensors include turbine, thermal mass, electromagnetic, ultrasonic, orifice plate, venturi. The different designs of the flowmeters have a variety of applications. With 4-20ma, RS485, or other output.

Then they all work differently. However, they can convert the flow signal into a digital display, or pulse, or 4-20mA signal.

Extended reading: Ultrasonic Flow Meters Types & Technical Guide

Sino-Inst is Manufacturer of Crude Oil Flow Meters. We supply more than 20 kinds of Crude Oil Flow Meters. 40% mass flowmeters,30% oval gear flow meters and other types of flowmeters.

Crude Oil Flow Meters are mainly used for flow measurement of high viscosity crude oil flow.

Crude Oil Flow Meters enable stable flow measurement without piping modifications. This greatly meets the measurement needs of many applications. Can be used from small to large tubes.

Sino-Inst’s Crude Oil 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 Crude Oil Flow Meter, level sensor, or other device, give us a call.

Request a Quote

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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.

Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.

RFQ Pressure Transmitters

Pressure Transducer Wiring Diagram Guide: 2 Wire-3 Wire-4 Wire

Posted on September 6, 2022 by KimGuo11

After the Pressure Transducer is installed, how should I wire it? Pressure sensor wiring refers to the electrical connection of the pressure sensor. A pressure transmitter is a conversion device that converts a pressure signal into an analog signal or a digital signal. Common signals include 4-20mA, 0-10V, 0-5V and other signals. The wiring methods of these signals generally include two-wire system, three-wire system, and four-wire system.

Many beginners struggle with sensor/transmitter wiring issues. Worry that the wrong connection will cause damage to the sensor/transmitter and affect the accuracy of the measurement. This article will discuss with you the wiring of pressure sensor/transmitter. Teach you how to deal with the wiring problems of two-wire, three-wire and four-wire sensors/transmitters.

Featured Pressure Transducer for Sale

**High-Temperature Pressure Transmitter**

**Combined Pressure and Temperature Sensor-Dual function**

**Explosion-proof Pressure Transmitter**

**Remote Diaphragm Seal Pressure Transmitter**

Pressure transducer is also called pressure transmitter.
A pressure transmitter is a device that converts pressure into pneumatic or electric signals for control and remote transmission.
It can convert physical pressure parameters such as gas and liquid sensed by the load cell sensor into standard electrical signals (such as 4~20mADC, etc.). It can be used to supply secondary instruments such as indicating alarms, recorders, and regulators for measurement and indication. and process regulation.

4-20mA pressure transmitter

4-20mA means that the minimum current is 4mA and the maximum current is 20mA.

The industry generally needs to measure various non-electrical physical quantities, such as temperature, pressure, speed, angle, etc. They all need to be converted into analog electrical signals before they can be transmitted to the control room or display equipment hundreds of meters away. This device that converts physical quantities into electrical signals is called a transmitter. The most widely used in the industry is to use a 4-20mA current to transmit analog quantities.

Because 4-20mA signals are least affected by electrical noise and resistance in the signal line, these sensors are best used when signals must be transmitted over long distances. These sensors are typically used in applications where the lead must be 1000 feet or more.

Extended Reading: strain gauge pressure transducer

When we talk about 2-wire, 3-wire and 4-wire transmitters, we are primarily referring to the way the transmitter is electrically connected and powered.
Here are their basic differences:

2-wire transmitter:

The power and signal outputs share two cables.
Usually the output is a 4-20mA current signal.
Since it requires only two cables, installation is relatively simple and low-cost.
Widely used in most process control applications.

3-wire transmitter:

There are usually two wires for power and one wire for output signals.
The output is usually voltage type, such as 0-10V.
Compared with 2-wire transmitters, 3-wire transmitters have separate power supplies and signals. Therefore, they may be more suitable in certain applications.

4-wire transmitter:

There are two wires for power and two wires for signal output.
Can output voltage or current signal, such as 4-20mA or 0-10V.
Due to their separate power and signal lines, 4-wire transmitters can often offer more functionality and performance, such as higher accuracy, remote configuration or HART communication.

Pressure sensor pinout refers to the pin layout or connection definition of the pressure sensor. You may also have heard of “4 pin pressure sensor” or “3 pin pressure sensor”.

The pin definition of the pressure sensor will tell the user the function of each pin or terminal. For example, which is the positive power supply (V+ or VCC), which is the ground (GND), which is the signal output, etc. Understanding these definitions is critical to properly connecting and using pressure sensors.

Here are some common pin definitions:

V+ or VCC: positive power supply. The sensor requires a power input.
GND or V-: Negative power supply or ground wire.
OUT or SIGNAL: signal output. This is the electrical signal output that the sensor converts into based on the measured pressure.
Other pins: Some pressure sensors may have pins with other functions, such as temperature output, I2C or SPI communication interface, etc.

“Instrument wire system” refers to the number of wires used for instrument power supply and standard signal transmission.

The name of the wire system is only after the birth of the two-wire transmitter.

This is the result of the widespread application of electronic amplifiers in instruments. The essence of amplification is an energy conversion process, which cannot be separated from power supply.

Therefore, the first appeared is the four-wire transmitter. That is, the two wires are responsible for the power supply. The outer two wires are responsible for outputting the converted and amplified signals (such as voltage, current, etc.).

Extended reading: Pressure Sensor Applications-Featured Industry Applications

2 wire pressure transducer wiring diagram

The wiring of the two-wire transmitter is shown in the figure. Power supply is 24VDC. The output signal is 4-20mA. The load resistance is typically 250Ω. The 24V supply has the lowest negative wire potential. It’s the public point.

The smart transmitter can also load the FSK keying signal of the HART protocol on the 4-20mA signal. Some digital display meters have transmission function or 24V power supply function. The function is similar to that of a two-wire transmitter.

The power supply and current signal loop of the two-wire transmitter are:
The positive terminal of the 24V power supply → the positive terminal of the transmitter → the negative terminal of the transmitter → the positive terminal of the digital display meter → the negative terminal of the digital display meter → the negative terminal of the 24V power supply, the digital display meter receives the current signal.
If a resistor R is connected in parallel with the positive and negative terminals of the digital display. The digital display meter receives the voltage signal.

Extended reading: High accuracy pressure transducers

3 wire pressure transducer wiring diagram

The positive terminal of the power supply of the three-wire transmitter uses one wire. Use a line for the positive end of the signal output. The negative terminal of the power supply and the negative terminal of the signal share a line. as the picture shows. The power supply is mostly 24VDC, and the output signal is mostly 4-20mA.

The power loop of the three-wire transmitter is:
24V power supply positive terminal→transmitter positive power supply wiring V+ terminal→transmitter negative terminal (common terminal)→24V power supply negative terminal.

The current signal loop is:
Transmitter’s current output I+ positive terminal → digital display meter positive terminal → digital display meter negative terminal → transmitter’s negative terminal (common terminal), the digital display meter receives the current signal.

If a resistor R is connected in parallel with the positive and negative terminals of the digital display meter, the digital display meter receives the voltage signal.

Read more about: What Is 0-10V Signal Output?

4 wire pressure transducer wiring diagram

The power supply and signal of the four-wire transmitter use two wires each, and the power supply and the signal work separately. As shown in the figure, most of the power supply is 220VAC, and there are also 24VDC. The output signal is mostly 4-20mA.

The current signal loop of the four-wire transmitter is:
The current output positive end of the transmitter → the positive end of the digital display meter → the negative end of the digital display meter → the negative end of the transmitter, the digital display meter receives the current signal.

If a resistor R is connected in parallel with the positive and negative terminals of the digital display meter, the digital display meter receives the voltage signal.

Extended reading: Troubleshooting For 4-20ma Pressure Transmitter

Frequently
Asked
Questions

The working principle of the pressure transducer is to convert the weak non-electrical pressure-pressure variable collected by the sensor into a transmissible standardized signal output.

At the same time, it is enlarged to supply secondary instruments such as indicating alarms, recorders, and regulators for measurement, indication and process adjustment.

The converted electrical signal has a certain continuous functional relationship (usually a linear function) with the pressure variable.

The pressure transmitter is mainly composed of three parts: the sensitive element, the sensing element and the measurement conversion circuit.

Extended Reading: Smart pressure transmitter

Two-wire transmission has specific requirements for its minimum supply voltage, output current, and transmitter power consumption.

Only when these three conditions are satisfied in the design can the two-wire transmission be realized. The four-wire system requirements are not as high as the two-wire system.

Therefore, the two-wire system and the four-wire system have different requirements for the electronic components of the whole circuit.

For the two-wire instrument, the output signal is mostly 4-20mA (there are also frequency signal output).

But the four-wire instrument has more output signals, such as current signal 4-20mA, 0-10mA, voltage (millivolt) signal, frequency signal, etc.

Our pressure transmitters can also be upgraded to Low power-battery powered Wireless Pressure Sensors.

For a 2-wire pressure transmitter, there are usually two wires. The positive wire is connected to the positive pole of the power supply and outputs the signal, and the negative wire is connected to the negative pole of the power supply or ground.
For 3-wire or 4-wire pressure transmitters, connect the power supply wire and signal output wire respectively according to the instructions in the manual.

Pressure transmitters usually have 2, 3 or 4 wires. It depends on the model and function.

A common electrical output from a pressure transmitter is a 4-20mA current output. But there are also models with 0-10V, 0-5V and other voltage outputs.

Yes, the pressure transmitter requires a power supply. A 2-wire transmitter supplies power and transmits signals simultaneously via its two wires. 3-wire and 4-wire transmitters usually have dedicated power supply lines.

The 3-wire 4-20mA transmitter usually has a dedicated power supply line, and the other two lines are the ground wire and the signal output line. This is different from a 2-wire transmitter, where power and signal share two wires.

Connect the signal output line of the pressure transmitter to the analog input of the VFD. Make sure the transmitter ground wire is connected to the VFD ground. In the parameter settings of the VFD, configure the corresponding analog input as pressure feedback, and adjust the parameters as needed.

Pressure Transducer Wiring is actually very simple. Generally, when the pressure transmitter is used and installed, there will be an installation manual, which can be installed directly according to the manual.

Pressure transmitters include capacitive pressure transmitters and resistive pressure transmitters. A pressure transmitter is a device that converts the pressure of a gas or liquid into a usable electrical signal.

The pressure transmitter can be divided into two-wire system, three-wire system and four-wire system according to the wiring method.

The pressure transmitter has two power lines and two signal lines. The power supply is connected to 24v DC. The simple detection method is to use an ammeter or voltmeter to connect both ends of the signal line.

After the pressure transmitter power supply is connected, the ammeter will have 4ma current or the voltmeter will have 0v or 1V voltage. Read more about: What Is 0-10V Signal Output?

The current transmitter generally has 4 terminals. Two are wired. The other two do not need to be wired. The DC24V power line of the transmitter is also a 4-20mA signal feedback line.

That is to say, the AI point of your secondary meter or DAS (data acquisition system) should have a DC24V feed output.

Generally, the 4-20mA pressure transmitter is a 2-wire system, powered by 24V, and outputs a 4-20mA current signal. After the pressure transmitter arrives at the scene, many people do not know how to wire it. This is a very painful and headache.

In fact, when you open the back cover of the pressure transmitter, you will see four terminals. OUT positive and negative and TEST positive and negative. Here we take OUT positive and negative.

TEST positive and negative is the factory, the manufacturer used to calibrate the pressure transmitter. It is not necessary to control the function of the two terminals when using it on site.

Direct OUT positive and negative on the line.

Extended Reading: Fluid pressure sensor

Non Contact Level Transmitters: Types & Industrial Applications

Posted on September 5, 2022 by KimGuo11

Non Contact Level Transmitters are now more and more widely used in industrial level monitoring. We most often provide customers with non-contact radar level transmitters and ultrasonic level meters. Both liquids and solids can be measured with Non Contact Level Transmitters. There is no need to dig the level probe deep into the measured medium. The sensitive elements measured by Non Contact Level Transmitters are not in contact with the liquid being measured. It can be used in special occasions that contact measuring instruments cannot meet. Such as the medium with high viscosity, strong corrosiveness, strong pollution and easy crystallization.

RFQ Level Meters

Featured Non Contact Level Transmitters for Sale

**SI-FMF11 FMCW Radar Level Transmitter 120GHz**

**SIRD-905 Horn Antenna Radar Tank Level Sensor**

**SIRD-802 Radar Level Sensor for Corrosive Liquids**

**SIRD-806 Radar High Temperature Level Sensor**

**ULT-100A Ultrasonic Level Transducer**

**ULT-200A Ultrasonic fuel tank level sensor**

**Portable Ultrasonic Liquid Level Indicator**

**HS-2000 Ultrasonic Tank Level Sensor-External Mounted**

Non Contact Level Transmitters Types

In order to choose the most suitable level sensor, we not only need to know the properties and state of the liquid being measured. It is also necessary to understand the advantages and disadvantages of different level sensors. in order to select the most suitable sensor. Next, let’s briefly introduce the common non-contact liquid level measurement methods and their characteristics.

Common non-contact measurement methods mainly include ray level meter, ultrasonic level meter, laser ranging sensor and radar level meter.

The rays emitted by nuclear radiation (such as gamma rays, etc.) have strong penetrating ability. And through the medium of different thickness has different attenuation characteristics. The nuclear radiation level meter uses this principle to measure the liquid level.

The nuclear radiation source of the nuclear radiation level gauge is installed outside the oil tank with a point or narrow structure. The elongated nuclear radiation source detection element is also installed outside the oil tank. It can realize the detection of dynamic change of liquid level.

In addition to measuring with nuclear radiation rays, neutron rays can also be used to measure liquid level.

The ray level meter is very convenient to install and has high measurement accuracy.

Because it does not have any parts in direct contact with the measured object. It is especially suitable for measurement problems that cannot be solved by traditional measuring instruments.

Extended reading: liquid nitrogen level measurement

The propagation speed of ultrasonic waves in the same medium is relatively constant. Reflection occurs when it encounters the surface of the object being measured. Based on this principle, an ultrasonic level meter was developed. It calculates the liquid level height by detecting the time difference between ultrasonic transmission and reflection. Therefore, it is easily affected by the energy loss of ultrasonic propagation.

The ultrasonic level meter has the characteristics of easy installation and high flexibility. However, when used in environments containing steam and powder layers, the detection distance will be significantly shortened. Not recommended for use in absorbing environments such as foam.

In addition, the accuracy of the ultrasonic level meter is slightly lower than that of the radar level meter, and the price is moderate.

Extended Reading: How to Measure Volume of Liquid

Its measurement principle is similar to that of an ultrasonic level meter. Just use light waves instead of ultrasound. The emission sensor emits laser light and irradiates it to the liquid surface to be measured. Reflection occurs at the liquid surface, and the receiving sensor receives the reflected light. Convert the time from transmit to receive to level.

The beam of a laser is narrow, so its spot is small and concentrated. Therefore, it is very suitable for containers with narrow openings and measurement objects with high temperature and high viscosity.

Laser ranging sensor level meters are easy to install, calibrate, and flexible. The price is relatively affordable, and it can be used for continuous or limit alarms of bulk materials or liquid levels.

If it is a transparent liquid and oil, it is necessary to add a reflective buoy on the liquid surface before it can be measured. Not suitable for use in foam or steam environment (cannot penetrate foam or easily disturbed by steam), fluctuating liquid (easy to cause malfunction), vibration environment, etc.

Radar level meters usually use the principle of frequency modulation radar. Utilize synchronous FM pulse technology. Mount the microwave transmitter and receiver on the top of the tank. A frequency-modulated microwave signal is emitted to the liquid surface.

When the echo signal is received, due to the delay of the round-trip propagation time. The transmission frequency has changed. The two signals are mixed and processed, and the difference frequency of the obtained signal is proportional to the distance between the tank top and the liquid surface.

The radar level meter has a large measurement range and is not affected by harsh weather environments. And easy to install, low maintenance and other advantages,

Especially suitable for high viscosity or high pollution products, such as asphalt. Radar level meters provide high measurement accuracy and do not require regular maintenance and recalibration. But the installation is more complicated and the price is relatively high.

Extended reading: Oil-water interface measurement-Magtech magnetic level indicator

Radar Type Level Transmitter Working Principle

Radar Level Measurement and guide wave radar level measurement Image source: https://instrumentationtools.com/radar-level-measurement/

Very short microwave pulses with very low energy are transmitted and received through the antenna system. The radar wave runs at the speed of light. The operating time can be converted into level signals by electronic components. A special time extension method can ensure stable and accurate measurement in a very short time.

Electromagnetic waves propagate in the air at the speed of light. The distance between the radar level gauge and the surface of the material can be expressed by the following formula: 　　

D = (1/2)*CT

In the formula:

D ———the distance between the radar level gauge and the surface of the material; 　　

C ———Speed of light 　　

T ———Pulse time.

Then the liquid level is: 　　L = E-D

In the formula:

L — liquid level; 　　

E ———The total height of the tank; 　　

D ———Air height.

Even in the presence of false reflections, the new micro-processing technology and the unique ECHOFOX- software can accurately analyze the level echo. By inputting the size of the container, the distance value can be converted into a signal proportional to the level. The instrument can be debugged with empty positions.

Extended reading: Amazing Solutions for Continuous Liquid Level Measurement

Ultrasonic Level Transmitter Working Principle

The working principle of the ultrasonic level sensor is:

Ultrasonic transducer (probe) emits high-frequency pulse sound waves, and the surface of the measured level (material) is reflected back. The reflected echo is received by the transducer and converted into an electrical signal. The propagation time of the sound wave is proportional to the distance from the sound wave to the surface of the object.

The relationship between the sound wave transmission distance S and the sound speed C and the sound transmission time T can be expressed by the formula: S=C×T/2.

Image Source： https://www.coulton.com/beginners_guide_to_ultrasonic_level_transmitters.html

The probe part emits ultrasonic waves, which are then reflected by the liquid surface. The probe part is received again. The distance from the probe to the liquid (object) surface is proportional to the elapsed time of the ultrasonic wave:
hb = CT2
Distance [m] = time × speed of sound/2 [m]
The temperature compensation formula of sound velocity:
Ambient sound velocity = 331.5 + 0.6 × temperature

Non Contact Level Transmitters Industrial Applications

Sino-Inst’s Non Contact Level Transmitters, whether ultrasonic level meter or radar level meter, are widely used in various industries.

Highly toxic medium
Bromine
liquid chlorine
Liquid ammonia
dimethyl ether

Oil, flammable and explosive media
gasoline and diesel
crude
heavy oil

Volatile media in pressure vessels
liquefied gas
C4
acrylic
liquified natural gas

Corrosive media
Anhydrous hydrogen fluoride
Bromine

Other media
methanol
fuel styrene
wax oil
Acetylene

Chlor-alkali
Storage and transportation
petrochemical
Coal chemical industry
oil refining
Fluorine chemical
fertilizer
pesticide
electricity
liquid storage
other industry

Extended reading: Oil-water interface measurement-Magtech magnetic level indicator

Frequently
Asked
Questions

Non contact level sensor refers to a type of level meters that the liquid level sensor does not need to contact the measured medium during measurement.
Common Non contact level sensors include ultrasonic level meters and radar level meters.

Extended Reading: Silo/Bin material level measurement system

There are 7 main types of level transmitters that Sino-Instrument offers. Each type of transmitter works in a different way, and makes it useful for different types of processes.

For more about: Types of Level Transmitters

Non contact water level sensor refers to the radar water level sensor. Radar Water Level Sensor is suitable for water level monitoring of lakes, rivers, reservoirs, open channels, and tidal water levels.

Radar Non-Contact Water Level Sensor adopts a non-contact measurement method and does not touch the water body. It is not affected by water quality, sediment and floating objects. The RS-485/RS-232/4-20mA interface can realize data long-distance wired transmission or docking with SCADA hydrological telemetry system. The measuring distance can be up to 70 meters.

Extended Reading: Dielectric constant for radar level transmitter

The non-contact liquid level meter has its unique advantages. There is no need to install the sensor on the tank wall during installation, and the instrument does not contact the liquid medium in the container. It effectively solves the technical problem of measuring liquid level under special harsh and harsh conditions such as strong corrosion, high toxicity, high pressure, flammability and explosion, high purity, and no bacterial infection.

Extended reading: Capacitance level sensor advantages and disadvantages

Read more about: River Water Level Monitoring System

Sino-Inst is Manufacturer of Non Contact Level Transmitters. We supply more than 20 kinds of Non Contact Level Transmitters. 40% ultrasonic level meters, 40% radar level transmitters and 20% other types of flowmeters.

Non Contact Level Transmitters are mainly used for level measurement of various liquids and solid particles.
It can measure even liquids such as water, seawater, oil, and slurry.

Non Contact Level Transmitters enable stable level measurement without tank modifications. This greatly meets the measurement needs of many applications. Can be used from small to large tanks.

Sino-Inst’s Non Contact Level Transmitters, made in China, Having good Quality, With better price. Our level 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 Non Contact Level Transmitters, flow sensor, or other device, give us a call.

Request a Quote

Please enable JavaScript in your browser to submit the form

High Accuracy Pressure Transducers

Posted on August 21, 2022 by KimGuo11

High Accuracy Pressure Transducers are also called high precision pressure transducers or high accuracy pressure sensors. Sino-Inst manufactures various types of High Accuracy Pressure Transducers.

From the perspective of accuracy, the accuracy of conventional pressure transmitters is 0.5%. Therefore, pressure transmitters can be divided into high-precision pressure transmitters (0.1% or 0.2% or 0.075%) and general pressure transmitters ( 0.5%).

High Accuracy Pressure Transducers support mV/V, V, mA and digital outputs. Ideal for applications requiring very high precision measurements such as oil, gas and geothermal energy exploration.

Checklist: Pressure Transmitter 4-20mA Common Faults and Error

Featured High Accuracy Pressure Transducers for Sale

**SI-703 Flush diaphragm pressure sensor**

**SI-706 Combined Pressure and Temperature Sensor-Dual function**

**SI-512H High Temperature Pressure Sensor**

**Flange Mounted Differential Pressure Transmitter**

**Differential pressure(DP) level transmitter**

When ordering a pressure transmitter, you can often be asked what accuracy pressure transmitter you need. Then our sales engineer will tell you that we have 0.5% accuracy and 0.1% accuracy. Even higher precision ones can be customized.

Also, different accuracy may affect the price of the pressure transmitter. So what is the accuracy of the pressure transmitter? Do we need to blindly pursue higher-precision pressure transmitters?

Extended Reading: 4-20ma pressure transducer wiring diagram

What is the accuracy of a pressure transmitter?

The accuracy of the pressure transmitter is the same as that of all measurement and display instruments, and it is an indicator of the reliability of the measured value of the instrument.

The instrument has a maximum allowable error (deviation), and the probability of more than 98% of the results obtained from N times of measurements on the same measured value does not exceed this range.

Maximum allowable error / measuring range * % = meter accuracy

For a pressure transmitter with an accuracy of class 0.1,

Output allowable error = output range * instrument accuracy% = 16 * 0.001 = 0.016 (mA)

That is, the maximum possible error when this meter is measured is plus or minus 0.065mA.

Extended reading: Pressure Sensor Applications-Featured Industry Applications

A pressure transmitter in the general sense is mainly composed of a load cell sensor (also called a pressure sensor), a measurement circuit and a process connection. It can convert physical pressure parameters such as gas and liquid sensed by the load cell sensor into standard electrical signals (such as 4~20mADC, etc.) to supply secondary instruments such as indicating alarms, recorders, and regulators for measurement and indication. and process regulation.

The pressure transmitter is an instrument that accepts pressure variables and converts the pressure changes into standard output signals in a certain proportion after sensing and conversion. The output signal of the transmitter is transmitted to the central control room for pressure indication, recording or control.

Usually, when considering the overall accuracy of the pressure transmitter, the factors that affect the accuracy of the pressure transmitter generally need to be considered.

According to the experience of Sino-Inst, we believe that everyone should choose the tolerance of the pressure transmitter according to the requirements of the industrial process. Instead of selecting according to the pressure transmitter indicators installed in the field.

Extended reading: Water Pressure Sensors for Measurement of Water Pressure

Factors affecting the overall accuracy of pressure transmitters

In the pressure transmitter manual or website, there is usually a separate and limited description of the accuracy. It might be called “reference precision” or something similar. But this only includes some of the factors that affect accuracy, not all. For example it only includes nonlinearity, hysteresis and repeatability.

This “best accuracy” does not take into account all factors that affect accuracy in practice (installation location, ambient temperature, etc.).

Therefore, do not think that the pressure transmitter is installed in an industrial process. This precision can be achieved in practical applications.

For a high-accuracy pressure transmitter, the “best accuracy” might be 0.04% or 0.025% of the pressure span.

The best (reference) accuracy is generally only for a few pressure ranges, not the full pressure range. And, it may vary with different pressure types. That is, the absolute range is not necessarily equal to the full range.

Accuracy specifications may be doubled or tripled for different ranges.

So make sure you know the accuracy for the pressure range/model you are using.

Extended Reading: strain gauge pressure transducer

The HART intelligent pressure transmitter can rescale its accuracy range in any ratio. Pressure transmitters can typically be scaled by 100:1 or higher adjustment specific gravity. Accuracy specifications typically give either full scale or a limited turndown ratio.

If the HART smart pressure transmitter is re-ranged to less than full scale, the accuracy specification will usually be degraded.

Therefore, if you re-range the pressure transmitter to less than the maximum range, you need to confirm how much accuracy error is incurred.

Most pressure transmitters in use are subject to changing environmental conditions. Likewise, the temperature of the pressure medium may vary considerably during use.

Like most measuring devices, pressure transmitters usually have some kind of temperature coefficient, a factor that affects accuracy depending on the ambient temperature. This temperature-dependent property seems to be commonly specified in an incomprehensible expression.

But try to understand this, and if you can’t figure this out, ask the pressure transmitter manufacturer.

It may vary from 0.01% to 0.5% of span for different pressure transmitters.

The worst-case pressure model indicated temperature effects may exceed 1% of range.

You should take this into account if the temperature varies widely during use.

The differential pressure transmitter can be used under the condition of pipeline static pressure. This means that both inputs have a certain pressure, and the differential pressure transmitter measures the difference between the two inputs. It is different from a transmitter that measures pressure under atmospheric conditions or a transmitter that measures absolute pressure under complete vacuum conditions.

An ideal differential pressure transmitter can only measure the difference between the inputs. But static line pressure actually has some effect on the output. If both inputs are at atmospheric pressure, the differential pressure is naturally zero.

Likewise, if the same pressure (say 50 bar/psi) is applied to both inputs, the differential pressure is still zero.

In fact, static pressure will have a certain effect on the output of the transmitter.

Therefore, when the static pressure changes, the differential pressure transmitter output also changes slightly.

Static pressure effects typically vary from 0.025% to 0.4% of span, depending on the differential pressure transmitter model.

Static pressure generally mainly changes the zero position of the differential pressure transmitter without significantly affecting the measurement full scale. Therefore, in the calibration process, after applying the same pressure (high pressure or low pressure) to both input terminals, observe the change value of the zero position of the differential pressure transmitter to verify this effect.

Line pressure may also have an effect on the measuring range of the differential pressure transmitter, which increases the difficulty of operation and calibration. It needs to be calibrated using a differential pressure standard.

More About: Differences! Static pressure vs dynamic pressure vs total pressure.

All measuring equipment will gradually lose accuracy over time. Some increase, some decrease. The same goes for pressure transmitters. Some pressure transmitters have a one-year stability guarantee, and some are even 5 or 10 years or more.

For example, a pressure transmitter with a reference accuracy of 0.04% of span can have an annual stability of 0.2% of span. For some other models, 0.2% span stability can be effective for 5 or even 10 years.

Depending on how often the pressure transmitter is recalibrated, you should consider long-term stability effects, as the pressure transmitter may drift significantly before the next recalibration (and possibly trim).

The installation location often affects the accuracy of the pressure transmitter. Most pressure transmitters will specify a mounting location.

Changing the installation orientation will generally cause the zero position of the pressure transmitter to change, but will not affect the accuracy of the full scale measurement. In fact, the mounting orientation of the pressure transmitter does not change during normal use. The location of the pressure transmitter should be considered when the pressure transmitter is calibrated in the workshop and installed in an industrial process, or when the pressure transmitter is removed from an industrial process for recalibration.

Of course, if the transmitter is a remote differential pressure type, the installation position of the capillary will have a great influence on the zero value. Again, this isn’t something that doesn’t change during normal use. Calibration may be affected if the remote differential pressure transmitter is removed from the installation location.

Many pressure transmitters specify vibration effects. Of course, this only needs to be considered when the pressure transmitter is installed in a vibrating location. The effect of vibration on accuracy is usually small, eg “less than 0.1% of span”.

The two-wire pressure transmitter will not work when the external power supply is not connected. The common power supply is 24VDC power supply. Pressure transmitters can usually operate over a wide supply voltage range, even down to 10 VDC. However, when the supply voltage changes during operation, it has little effect on the accuracy of the pressure transmitter.

For example, it can be specified as “every 1V of power supply voltage will produce less than 0.01% change of measurement range”. In fact, when the power supply can be used normally, there is generally no problem.

The index parameters of the overall accuracy of some pressure transmitters contain several common factors that affect the accuracy. These include the “reference accuracy” mentioned above and the effect of ambient temperature and static/line pressure. This overall accuracy is easier to grasp because it is closer to what a pressure transmitter can achieve.

For example, an “overall accuracy” specification might be 0.14% of span, while the reference value is 0.04%. Therefore, once temperature and line pressure effects are included, the reference accuracy is multiplied by 3-4.

Another example is that there is a 0.075% range reference accuracy, when the temperature effect is considered, the accuracy is reduced to 0.2% of the range, and when the static pressure effect is further considered, the accuracy is reduced to 0.3% of the range.

If the index parameters of the overall accuracy of the pressure transmitter are clear. This will help you gain an in-depth understanding of the type of accuracy that can be achieved in practice. Even these overall accuracies are often missing some of the factors listed in this paper.

When using a pressure transmitter to measure pressure, there is a risk that the membrane of the transmitter will be contaminated by the pressure medium or some dirt. Such contamination can seriously affect the accuracy of the pressure transmitter.

Of course, this is not something that is explicitly stated. But it can also be considered a big risk in normal use, especially if you decide to recalibrate with a long period of time (eg, years). Therefore, in addition to the long-term drift indicator parameters of the pressure transmitter, this needs to be considered in the risk analysis.

If the pressure transmitter gets very dirty and starts to experience significant measurement errors, you will generally find this in the measurement results.

However, if it is only a small error, it is difficult to notice it in normal use.

Read more about: What Are 0-10V Pressure Transducers?

pressure transducer 4-20mA

Many friends have some misunderstandings about this issue, and feel that 4-20mAdc is more troublesome to calculate. So why use 4-20mAdc?

The field two-wire pressure transmitter needs power supply. First, it is necessary to ensure that there is still a certain current in the case of zero position. Then in the design, we found that the minimum starting current of the transmitter is 3.5mA, which means that the transmitter can still work under 3.5mA.

Then if it is 0mA, then there is no power supply and it cannot work.

So use 4mA as the zero position, if it starts at 0mA, the meter will not work. If there is a disconnection in the field, there is no way to tell if it is a problem with the meter or the power supply. Therefore, the international general standard starts from 4mA.

The second question, why is it 20mA? Why not 30mA? Why not 100mA?

It stands to reason that the bigger the better, the higher the resolution, but it is not.

Through the observation of the gas explosion point, it is found that the spark generated when the 20mA is switched on and off will not cause the gas explosion. 20mA is a critical value, so ≤20mA is safe. If >20mA, there will be an explosion problem, so 4-20mA is a better value.

Then there are also some occasions where 0-10mA is used, which is generally not used in the process industry. It may be used in the discrete industry. There are also some occasions where 0.5v-4.5v or 0-5v are used in the discrete industry. Then for the process industry, it is mainly 4-20mA.

Sino-Inst is a pressure transmitter manufacturer, the main products include intelligent pressure transmitter, digital pressure transmitter, high temperature pressure transmitter, sanitary pressure transmitter, compact pressure transmitter, liquid level pressure transmitter transmitter, differential pressure transmitter, etc., the product series is complete, high precision, welcome to inquire!

Extended Reading: Smart pressure transmitter

Frequently
Asked
Questions

In fact, we believe that there is no best pressure sensor, only the most suitable pressure sensor.
There are thousands of pressure sensor brands and models on the market. Each type of pressure sensor has its own advantages. Therefore, only a pressure sensor that satisfies specific measurement conditions is a suitable pressure sensor, that is, the best pressure sensor.

As long as we choose a pressure sensor, remember a few words: type, range, overload, medium, temperature, accuracy, signal, process connection. A suitable pressure sensor can be selected.

The high pressure sensor mainly measures pressure, that is, converts the measured pressure value into a current or voltage signal, and the converted current or voltage signal can be processed by the circuit and output to meet the standard.

Simply put, the function of the high pressure sensor is to feel the measured value within a specified range and convert it into a signal according to a certain law.

With the development of technology, high pressure sensor has the most primitive mechanical structure into the current semiconductor material structure. So its volume and weight are greatly improved. No longer as bulky and large as before. In addition, the sensitivity and accuracy are also greatly improved, and the installation and debugging are extremely convenient.

Read more about: Features of SI-702 High Pressure Sensor

The two most commonly used types of pressure sensors are diffused silicon and capacitive.

Pressure transmitters can be categorized into four main types:

Gauge Pressure Transmitter.
Absolute Transmitters.
Differential-Pressure Transmitter.
Multivariable Pressure Transmitters.

High pressure transducer is used to measure high pressure up to 1500Mpa. Also called ultra high pressure transducer.

High pressure transducer adopts ultra high pressure design. Suitable for high pressure applications up to 15000bar. SI-702S series ultra high pressure pressure transducer can provide reliable ultra-high pressure measurement. Ultra high pressure transmitter adopts rare metal alloy material. After special process treatment, integrated design. All stainless steel welding package. Laser resistance temperature compensation. With high performance digital processing circuit. The factory has undergone high and low temperature aging and long-term fatigue tests. Good long-term stability. Ultra-long working life. Maintain safe and stable operation in the ultra-high pressure range.

The pressure sensor converts non-electrical physical quantities such as gravity, pressure, liquid level, material characteristics, etc. into electrical signals or directly sends physical quantities such as pressure, liquid level, etc. to the pressure transmitter.

The pressure transmitter is to amplify the weak electrical signal collected by the pressure sensor in order to transmit or start the control element. Or a signal source that converts the non-electrical input from the sensor into an electrical signal and amplifies it for remote measurement and control. The analog quantity can also be converted into a digital quantity as required.

The pressure sensor and the pressure transmitter together constitute an automatically controlled monitoring signal source. Different physical quantities require different pressure sensors and corresponding pressure transmitters.

Flat Pressure Sensor for High Viscosity Fluids

Posted on August 16, 2022 by KimGuo11

Flat Pressure Sensor is a type of pressure sensor that specifically refers to the measurement diaphragm without pressure holes. Also known as a flat film pressure sensor.

Flat Pressure Sensor is a special pressure sensor most commonly used in industrial automatic control. It is widely used in the pressure measurement and control of viscous media such as chemical coatings, paints, mud, asphalt, crude oil, etc. It solves the problem that conventional products are easy to block and cannot be used continuously, etc. defect.

The Flat Pressure Sensor elastomer adopts imported materials, diaphragm isolation technology, no pressure holes in the test head, and no viscous medium clogging during the measurement process.

Main parameters of Flat Pressure Sensor

Range:	0-0.6, 1, 5, 10, 20, 30, 40, 50～200MPa
Comprehensive accuracy:	0.1%FS, 0.2%FS, 0.5%FS
Output signal:	4-20mA (two-wire system), 0-5/1-5/0-10VDC (three-wire system)
Supply voltage:	24VDC (10-30VDC)
Medium temperature:	-20～85℃～450℃
Ambient temperature:	-20～85℃
Load resistance:	current output type: maximum 800Ω; voltage output type: greater than 50KΩ
Insulation resistance:	greater than 2000MΩ (100VDC
Sealing class:	IP65
Long-term stable performance:	0.1%FS/year
Vibration influence:	within the mechanical vibration frequency of 20Hz ~ 1000Hz, the output change is less than 0.1%FS
Electrical interface:	metal sealed terminal, four-core aviation connector
Mechanical connection:	M20×1.5, G1/2-14, etc. Other threads can be customized according to customer requirements

Extended Reading: Fluid pressure sensor

Principle of Flat Pressure Sensor

The flat membrane pressure sensor test head adopts the pressure-free mode to ensure that there is no blockage of viscous media during the measurement process, and to ensure that the pressure detection works normally.

It adopts super-large diaphragm design, the core adopts highly sensitive material, diaphragm isolation technology, and integrated structure design.

The medium and high temperature pressure-sensitive chip and heat pipe structure are used in the measurement of high temperature medium, which effectively solves the drawbacks that the electronic components inside the sensor cannot withstand high temperature.

Extended Reading: Resistive Pressure Transducer

Application of Flat Pressure Sensor

Pressure measurement and control of viscous media such as chemical coatings, paints, mud, asphalt, and crude oil;
Viscous liquid, fluid;
It is suitable for pressure measurement and control in harsh working environment, explosion-proof and explosion-proof occasions;

Extended reading: LCD Display Oval Gear High Viscosity Flow Meter

We also supply a variety of chemical flow meters in corrosion-resistant materials.

More Featured Pressure Transmitters

**Remote Seal Differential Pressure Transmitter**

**Extended Diaphragm Seal DP Level Transmitter**

Frequently
Asked
Questions

Flow Meter Selection Guide 101: Find the Perfect Fit for Your Application

A pressure transducer often called a pressure transmitter, is a transducer that converts pressure into an analog electrical signal.

Although there are various types of pressure transducers, one of the most common is the strain-gage base transducer.

The conversion of pressure into an electrical signal, is achieved by the physical deformation of strain gauges, which are bonded into the diaphragm of the pressure transducer, and wired into a Wheatstone bridge configuration.

Pressure applied to the pressure transducer produces a deflection of the diaphragm, which introduces strain to the gages.

The strain will produce an electrical resistance change proportional to the pressure.

Extended reading: Pressure transmitter working principle

Fluid Pressure Sensors refers to sensors that can be used to measure the pressure of liquid media. Such as measuring pressure of Oil, Fuel and other fluid systems (select a sensor with the appropriate range for your system). Fluid Pressure Sensors have important uses. For example, the direct measurement of pressure in a fluid line. For example, put Fluid Pressure Sensors into the liquid, measure the liquid pressure, and estimate the liquid level. For example, by measuring the differential pressure of Fluid, the flow rate of the pipeline can be calculated.

Extended reading: How do fluid pressure sensors work?

There are many types of pressure sensors. Such as resistance strain gauge pressure sensors, semiconductor strain gauge pressure sensors, piezoresistive pressure sensors, inductive pressure sensors, capacitive pressure sensors, resonant pressure sensors, etc.

Extended reading: wireless pressure transmitter working principle

Currently, the most widely used pressure sensors include:

Diffused silicon piezoresistive pressure sensor,
Ceramic piezoresistive pressure sensor,
Sputtering thin film pressure sensor,
Capacitive pressure sensor,
Sapphire pressure sensor with high temperature resistance.
But the most widely used is the piezoresistive pressure sensor, which has a very low price, high accuracy and good linearity.

Extended Reading: Electronic Pressure Switch for Air Compressor

Non Contact Flow Meters Measure Liquid Flow

Posted on August 14, 2022 by KimGuo11

What is non contact flow meter?

Non Contact Flow Meters refers to flow meters that can achieve flow measurement without contacting the fluid medium. No need to destroy the pipeline. Easy to install and remove. This is a good choice for many pipes with strict hygiene requirements or only temporary measurements.
Non Contact Flow Meters supplied by Sino-Inst are suitable for various pipe material requirements: stainless steel pipe, carbon steel pipe, copper pipe, plastic pipe (PVC, PVDF, PPR, PPH, HDPE, etc.). It can also meet the measurement of different clean fluids: various acids, chemical solvents, alcohol, beverage water, Coca-Cola, etc.

RFQ Flow Meters

Featured Non Contact Flow Meters

Types of Non Contact Flow Meters

Currently, the main Types of Non Contact Flow Meters on the market are ultrasonic flow meters and radar flow meters.

Non-contact ultrasonic flowmeters account for 90% of non-contact measurement applications. Mainly used for flow measurement of various pipeline fluids.

Non-contact radar flowmeter is suitable for non-contact flow measurement of rivers, channels, pipelines, etc.

Clamp-on ultrasonic flowmeters utilize ultrasonic technology for easy and quick installation. Applicable to a variety of materials and pipes of different diameters. Delivers incredible measurement results even when compared to electromagnetic flow products.

The non contact ultrasonic flow meter only needs to install a very small ultrasonic sensor on the outside of the pipe without destroying the pipe. It can provide completely reliable measurement results while saving a lot of installation costs.

The transducer and the converter are connected by a special signal transmission cable. In the case of fixed measurement, a junction box should be installed in an appropriate place. Clamp-on transducers usually also require mounting clamps and couplant.

Extended reading: Totalizing flow meter water

Non-contact radar flowmeters are used for flow measurement in drains, drains, and rivers. Suitable for surface flow velocity for easy measurement. It can be used for long-term flow monitoring of various non-full drainage pipes, open channels (rectangular, trapezoidal, etc.), weirs, grooves, etc. and surface runoff. Instantaneous liquid level, flow rate and flow can be automatically recorded.

It can work stably in complex environments such as inspection wells that are wet, full of toxic and harmful, flammable and explosive gases. Due to non-contact, it is suitable for monitoring of fast flow monitoring points. And compared to contact equipment, installation and maintenance are simpler. But it cannot work under long-term immersion and overflow conditions.

It can meet the needs of system monitoring and data transmission without AC power and network access. And has excellent sealing performance, with anti-corrosion, explosion-proof function.

It can be maintenance-free on a daily basis, run regularly for inspection, and no need for manual on-duty. Measurement information can be stored locally and sent wirelessly. With early warning and cloud management functions, it can be set remotely.

Strap on Flow Meter for Small Pipes Φ9.53~Φ90

Strap on flow meter X3 is widely used in flow measurement and monitoring in the production process.

Strap on flow meter X3 can meet the needs of different pipe materials: stainless steel pipe, carbon steel pipe, copper pipe, plastic pipe (PVC, PPR, PPH, HDPE), etc.

Strap on flow meter X3 almost meets the measurement of different clean fluids: various acids, alcohols, chemical solvents, alcohol, drinking water, Coca-Cola water… etc.

Product	Strap on Flow meter
Model	X3
Flow range	0.1m/s~5.0m/s
Accuracy	±2.0%
Repeatability	0.80%
Pipe size	φ6.35~φ90
Data storage	Daily, monthly, and Annual. Flow Totalizer
Analog output	4~20mA, Maximum load: 600Ω
Alarm output	DCT, Upper and lower limit alarm function(optional)
Communication	RS485,support Modbus communication protocol
Power supply	24VDC
Cable length	2.0m
Keypad	Four light touch buttons
Screen	OLED 128*64 displayscreen
Units	Metric and imperial units are available, Cubic Meters(m3), Liters(L), USA Gallons(GAL)/hour,/min,Default unit setting:m3/h
Totalizer	Six bit digit
Piper material	Stainless steel pipe, carbon steel pipe, copper pipe, plastic pipe
Case material	Aluminum alloy
Environment temp.	0℃~50℃（32°F~122°F)
Medium temp.	0℃~50℃（32°F~122°F)
Environment humidit	0-95% relative humidity, without condensation
IP Grade	IP54

Extended Reading: Types Of Crude Oil Flow Meters

More Featured Liquid Flow Meters

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Guide for Digital Fuel Flow Meter
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Mechanical water flow meters refer to a type of flow meter suitable for clean water processes or applications. The working…
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Frequently
Asked
Questions

If you let me answer this question. I would like to divide flow meters into two categories: mass flow meters and volumetric flow meters.

Of course, it can also be divided according to the measurement medium. There are two types of flow meters for measuring gas and measuring liquid.

Perhaps, we can also divide into closed pipeline measurement and open channel measurement according to the situation of the pipeline.

Finally, we may also be able to divide into contact and non-contact measurements according to the contact situation of the medium.

Non-invasive flow meter is also known as non-contact flow meter. When measuring the fluid flow of the pipeline, there is no need to cut and open the pipeline. easy to use.

If the flowmeter is divided into 5 categories. Then the five commonly used flowmeters are:

Electromagnetic flowmeter
Differential pressure flowmeter
Turbine flowmeter
Ultrasonic flowmeter
Volumetric flowmeter (PD)

Extended reading: How to choose a high viscosity flow meter?

Sino-Inst is Manufacturer of Non Contact Flow Meters. We supply more than 20 kinds of Non Contact Flow Meters. 90% ultrasonic flowmeters, and other types of flowmeters.

Non Contact Flow Meters are mainly used for flow measurement of various liquids.
It can measure even liquids such as water, seawater, oil, and slurry.

Non Contact Flow Meters enable stable flow measurement without piping modifications. This greatly meets the measurement needs of many applications. Can be used from small to large tubes. For efficient non-contact flow measurement of flexible and rigid plastic pipes.

Sino-Inst’s Non Contact 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 non-contact flow sensor, level sensor, or other device, give us a call.

Request a Quote

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What Is Resistive Pressure Transducer?

Posted on August 4, 2022 by KimGuo11

What Is Resistive Pressure Transducer?

Resistive pressure transducers are also called resistance pressure transducers. It is a commonly used pressure sensor. Pressure sensors are generally distinguished by principle: capacitive pressure transmitters, resistive pressure transducers, inductive pressure transmitters, semiconductor pressure transmitters, and pressure transmitters for high-frequency measurement. Among them, resistance pressure transmitters are commonly used.
Resistance strain pressure sensor is a kind of resistance pressure sensor. It measures the pressure value by the resistance change of the strain gauges bonded to the elastic element.

Featured DP transmitters.

Resistive Pressure Transducer Working Principle

The functional principle of a resistive pressure transducer is very simple. A pressure sensor converts a mechanical pressure value into a proportional electrical signal. Pressure sensors usually consist of a body and a (thin) diaphragm.

The electrical components of resistance pressure transmitters that feel pressure are generally resistance strain gauges. Resistance strain gauges are sensitive devices that convert the pressure on the measured component into an electrical signal.

The diaphragm is the most important element for pressure measurement and is equipped with strain-sensitive and piezoresistive structures, so-called strain gauges. The diaphragm deflects under pressure.

The most widely used resistance strain gauges are metal resistance strain gauges and semiconductor strain gauges. There are two types of metal resistance strain gauges: filamentary strain gauges and metal foil strain gauges.

Usually, the strain gauge is tightly bonded to the matrix that generates mechanical strain through a special adhesive. When the stress of the matrix changes, the resistance strain gauge also deforms together, which changes the resistance value of the strain gauge. The voltage across the resistor changes.

For example, if a resistor is connected to a Wheatstone measurement bridge, an electrical signal can be measured and transmitted to the indicator.

Extended reading: High accuracy pressure transducers

Types of Pressure Transducers

Let’s talk about the classification of transmitters:

According to the working principle of the sensor, it can be divided into resistance, capacitance, inductance, semiconductor, etc.;
According to the classification of sensor chips, it can be divided into metal, ceramic, diffused silicon, sapphire, etc.;
According to the measurement range, it can be divided into differential pressure, gauge pressure, absolute pressure, high static pressure and differential pressure, etc.;

Resistive pressure transducers are the most widely used transmitters and have the advantages of high cost performance and good linearity characteristics.

Extended Reading: 4 wire pressure sensor wiring diagram

Types of Resistance Pressure Transducers

Resistive pressure transducers are generally divided into metal, ceramic, and diffused silicon according to pressure-sensitive components.

The difference between the three:

The metal pressure transmitter has poor accuracy, but the temperature effect is small, and it is suitable for fields with a wide temperature range and low accuracy requirements.
The accuracy of ceramic pressure sensors is better, but it is greatly affected by temperature. Another advantage of ceramics is impact resistance and corrosion resistance.
Diffusion silicon pressure transmitter has high precision and large temperature drift, so it is generally necessary to perform temperature compensation before it can be used. And even after temperature compensation, pressures above 125°C cannot be measured. However, under normal temperature conditions, the sensitivity coefficient of diffused silicon is 5 times that of ceramics. Therefore, it is generally used in the field of high-precision measurement, but the accuracy is low in the micro-range.

Extended Reading: Smart pressure transmitter

Piezoresistive pressure sensor refers to a sensor made by using the piezoresistive effect of single crystal silicon material and integrated circuit technology.

After the single crystal silicon material is subjected to the force, the resistivity changes, and the electrical signal output proportional to the force change can be obtained through the measurement circuit.

It is also known as a diffused silicon piezoresistive pressure sensor. It is different from the adhesive strain gauge, which needs to indirectly feel the external force through the elastic sensitive element, but directly feels the measured pressure through the silicon diaphragm.

Capacitive pressure transducer (capacitive type pressure transducer) is a pressure sensor that uses capacitive sensing elements to convert the measured pressure into an electrical output that has a certain relationship with it. The characteristics are that the input energy is low, the dynamic response is high, the natural effect is small, and the environmental adaptability is good.

It generally uses a circular metal film or a metal-plated film as an electrode of the capacitor. When the film is deformed by pressure, the capacitance formed between the film and the fixed electrode changes. By measuring the circuit, the output voltage has a certain relationship with the voltage. electric signal.

Capacitive pressure sensors belong to the polar distance variable capacitive sensors, which can be divided into single capacitive pressure sensors and differential capacitive pressure sensors.

Extended Reading: MEMS Pressure Sensors

The differential pressure transmitter is a transmitter that measures the pressure difference between the two ends of the transmitter, and outputs a standard signal (such as 4~20mA, 0~5V).

Differential pressure transmitters are different from general pressure transmitters in that they have 2 pressure interfaces. Differential pressure transmitters are generally divided into positive pressure ends and negative pressure ends.

In general, the pressure at the positive pressure end of the differential pressure transmitter should be greater than the pressure at the negative pressure section to measure.

The differential pressure transmitter is used to prevent the medium in the pipeline from directly entering the transmitter, and the pressure-sensitive diaphragm and the transmitter are connected by a capillary filled with fluid.

It is used to measure the liquid level, flow and pressure of liquid, gas or steam. Then convert it into 4～20mA DC signal output.

Potentiometric pressure transducers are usually used for displacement, level and angle measurement.

The measured component is connected to the rotating shaft (or sliding arm) of the potentiometer through a certain mechanical transmission part. When the measured change changes, the sliding arm moves, and the resistance from the center of the potentiometer to the two fixed ends changes differentially.

The resistance change of the potentiometer can be converted into a voltage change output through a voltage divider circuit or a bridge circuit, and after A/D conversion, the measured physical quantity can be accurately measured. !

The hydraulic pressure transducer is mainly used in the pressure measurement of industrial equipment such as construction machinery, special equipment, compressors, injection molding machines, and servo equipment. It has good waterproof, small size and high cost performance. It is easy to install. The whole structure is made of stainless steel, which has good sealing, vibration resistance and stable and reliable performance.

Hydraulic pressure transducer is the extension and development of pressure transmitter technology. According to the principle that the pressure generated by different specific gravity liquids at different heights is linear. Realize the accurate measurement of the volume, liquid height and weight of water, oil and paste. Measure and transmit.

Extended Reading: Liquid pressure sensor

Our pressure transmitters can also be upgraded to Low power-battery powered Wireless Pressure Sensors.

Strain Gauge Pressure Transducer Working Principle

The strain gauge pressure transducer works based on the principle of resistance strain effect.

There are two types of resistance strain gauges: metal strain gauges (wire or metal foil) and semiconductor strain gauges. The measured pressure strains the strain gauge.

When the strain gauge produces compressive strain, its resistance decreases. When the strain gauge produces tensile strain, its resistance increases.

The resistance value of the strain gauge changes, and then the corresponding millivolt-level potential output is obtained through the bridge circuit. The measured pressure is displayed by a millivoltmeter or other recording instruments. Thus, a strain gauge pressure gauge is formed.

Strain gauge structure: It consists of three parts: strain sensitive element, substrate and cover layer, and lead wire. Strain-sensitive elements are generally composed of metal wires and metal foils (high resistivity materials), which convert mechanical strain into changes in resistance. The substrate and cover layer serve to fix and protect sensitive components, transmit strain and electrically insulate.

Resistance strain pressure sensor structure: diaphragm type, cylinder type, combined type. Among them, the diaphragm type is suitable for low pressure measurement; the cylinder type is suitable for high pressure measurement.

The working mode of the resistance strain pressure sensor: the change of resistance is converted into the output of current or voltage signal through the unbalanced bridge.

Featured Air pressure transducer

**SI-300 Pressure Transducer 4-20mA/Voltage**

**SI-390 Industrial Pressure Transmitter**

SI-512H High Temperature Pressure Sensor

Featured Digital pressure transducer

**Diffused silicon Gauge Pressure Transmitter**

**Capacitive Gauge Pressure Transmitter**

**Hygienic / Sanitary Pressure Transmitter**

Frequently
Asked
Questions

Classification of working principle of pressure sensor

Piezoresistive pressure sensor
Ceramic pressure sensor
Diffusion silicon pressure sensor:
Sapphire pressure sensor:
Piezoelectric pressure sensor:

Extended reading: Pressure Sensor Applications-Featured Industry Applications

Using a multimeter to test the pressure sensor can only perform simple tests, and the test results are only for reference.
There are roughly three tests that can be performed:

Bridge detection:
It mainly detects whether the circuit of the sensor is correct. Generally, it is a Wheatstone full-bridge circuit, which uses the ohm gear of the multimeter to measure the impedance between the input terminals and the impedance between the output terminals. These two impedances are the input and output of the pressure sensor. impedance. If the impedance is infinite, the bridge is disconnected. It means that there is a problem with the sensor or the definition of the pin is not correctly judged;

Detection of zero point:
Use the voltage range of the multimeter to detect the zero output of the sensor without applying pressure. This output is generally a mV level voltage. If it exceeds the technical specifications of the sensor, it means that the zero point deviation of the sensor is out of range;

Pressure detection:
The method of checking the order is: supply power to the sensor, blow the air guide hole of the pressure sensor with the mouth, and use the voltage range of the multimeter to detect the voltage change at the output end of the sensor. If the relative sensitivity of the pressure sensor is large, this amount of change will be significant. If there is no change at all, you will need to switch to an air pressure source to apply pressure.

These types of sensors are also called pressure transmitters. Because 4-20mA signals are least affected by electrical noise and resistance in the signal line, these sensors are best used when signals must be transmitted over long distances. These sensors are typically used in applications where the lead must be 1000 feet or more.

Read more about: What Is 0-10V Signal Output?

What Is a Fluid Pressure Sensor?

Posted on July 25, 2022 by KimGuo11

What Is a Fluid Pressure Sensor?

Fluid Pressure Sensors refers to sensors that can be used to measure the pressure of liquid media. Such as measuring pressure of Oil, Fuel and other fluid systems (select a sensor with the appropriate range for your system). Fluid Pressure Sensors are also called liquid pressure sensor or liquid pressure transducer. Fluid Pressure Sensors have important uses. For example, the direct measurement of pressure in a fluid line. For example, put Fluid Pressure Sensors into the liquid, measure the liquid pressure, and estimate the liquid level. For example, by measuring the differential pressure of Fluid, the flow rate of the pipeline can be calculated.

Differential pressure flow meter advantages and disadvantages

What is a pressure sensor?

Typically, a pressure sensor (sometimes called a pressure transducer or pressure transmitter) is used to measure the pressure of a fluid (gas or liquid).
Pressure is an expression of the force required to stop a fluid from expanding, and is usually expressed in force per unit area.
Pressure sensors generate electrical signals related to the applied pressure. Such signals are usually digital or analog, but optical, visual and auditory signals are also common.
Industrial pressure sensors, also known as pressure transducers, pressure transmitters, pressure indicators and pressure switches.

Extended Reading: Smart pressure transmitter working principle

How do fluid pressure sensors work?

An instrument for measuring fluid pressure. Usually the measured pressure is compared to a reference pressure (such as atmospheric pressure or other given pressure), thus measuring the relative pressure or pressure difference.

According to the working principle, it can be divided into three types: liquid column, elastic and sensor.

The principle of the pressure sensor is to convert the pressure signal into an electrical signal. Such as strain type, elastic element deformation caused by resistance change. Piezoelectric, the use of piezoelectric effect.

Various pressure sensors can be miniaturized, more accurate and fast to measure, especially to measure dynamic pressure, realize multi-point inspection, signal conversion, long-distance transmission, computer connection, timely processing, etc., so as to develop rapidly and widely used.

Extended reading : Types of pressure sensors

Applications of fluid pressure sensors

Fluid pressure sensors are mainly used in: construction machinery, hydraulic and pneumatic systems, petrochemicals, energy and water treatment, water conservancy and hydropower, compressors and other fields:

In the hydraulic system, the pressure sensor is mainly used to complete the closed-loop control of the force. Extended reading: Hydraulic oil flow measurement solutions.

When the control spool moves suddenly, a peak pressure several times the working pressure of the system will be formed in a very short period of time.

In typical mobile and industrial hydraulics, any pressure sensor can quickly be destroyed if not designed with such extreme conditions in mind.

Shock-resistant pressure sensors are required. There are two main ways for pressure sensors to achieve shock resistance, one is a strain gauge chip, and the other is an external coil. Generally, the first method is used in hydraulic systems, mainly because Easy to install.

Another reason is that the pressure sensor is subject to constant pressure pulsations from the hydraulic pump.

Extended reading: extrusion melt pressure transducer

Fluid pressure sensors are often used in safety control systems, such as the safety management system of the air compressor itself.

In the field of security control, the application is generally considered from the performance aspect, as well as the safety and convenience of the actual operation.

The fluid pressure sensor can install some components and signal conditioners and other devices on a very small chip through materials and advanced processing technology. Therefore, its small size is also its advantage. Of course, it can also improve the accuracy of system testing to a certain extent. .

In the safety control system, the pressure brought by the compressor is controlled to a certain extent by installing a pressure sensor in the piping equipment of the air outlet. This is a certain protection measure and a very effective control system.

When the compressor starts normally, if the pressure value does not reach the upper limit, then the controller will open the air inlet and adjust the equipment to reach the maximum power.

Extended Reading: Resistive Pressure Transducer

Fluid pressure sensors play an important role in injection molds.

It is installed in the nozzle of the injection molding machine, the hot runner system, the cold runner system and the cavity of the mold to measure the distance between the nozzle of the injection molding machine and the cavity during the injection molding, filling, pressure holding and cooling of the plastic. plastic pressure.

Extended reading: High Pressure Hydraulic Flow Meter

There are many kinds of pressure sensors, for the special environment of mine pressure monitoring.

Mine pressure sensors mainly include: semiconductor piezoresistive pressure sensors, metal strain gauge pressure sensors, differential transformer pressure sensors, etc.

The above sensors are widely used in the mining industry, and the specific sensor to be used needs to be selected according to the specific mining environment.

Extended reading: High Pressure Flow Meters for Liquids-Steam-Gas

Pressure sensors are commonly used in air compressors, as well as air conditioning and refrigeration equipment. These sensor products are small in size and easy to install. In addition, the pressure guide port generally adopts a special valve needle design.

Extended reading: Pressure Sensor Applications In Various Industries

Read more about: Calculation Of Pressure Drop

Pressure Sensor For Liquid Level Measurement

In physics, the pressure P of a liquid is determined by the relationship: p=pgh.

For the same kind of liquid, the liquid density p is constant. Therefore, the pressure P of the liquid is linearly proportional to the height h of the liquid surface (the height from the liquid surface).

It is not difficult to find that the pressure of the liquid at different heights of the liquid level is also different.

As shown in the figure above, when the pressure sensor is used to measure the liquid level, the pressure sensor is installed at the bottom of the tank. When the liquid level in the tank changes, the height h from the tank bottom to the liquid level also changes at the same time, and the pressure naturally changes accordingly, thus achieving the purpose of continuous measurement.

One of the advantages of using pressure sensors for liquid level measurement is non-contact. Compared with mechanical and static methods, when measuring, it does not require too many parts to contact the liquid, and the installation is relatively convenient.

In addition, in terms of measurement principle, compared with similar non-contact measurement methods such as laser and ultrasonic, the relationship of pressure sensor measurement principle is simpler and linear, and it is more intuitive in data processing, analysis and processing.

Extended reading: Differential pressure level transmitter working principle

Pressure Sensors For Flow Measurement

The pressure of the fluid is an extremely important parameter in flow measurement. Differential pressure flowmeter uses the pressure difference at both ends of the throttling element to realize flow measurement.

In addition, the working pressure of the flowmeter can be known through pressure measurement, and necessary correction calculations are performed to ensure the accuracy of flow measurement.

Extended reading: flow rate and pressure relationship

Upstream and Downstream Flow Straight Pipe Requirements-for Flowmeter Installation

fluid depth pressure sensor

If we make the pressure sensor into a submersible sensor, it can be used to measure the depth of the liquid.

The most common fluid depth pressure sensor is what we often call the submersible hydrostatic pressure sensor. Used to measure the depth or level of liquids such as water, fuel.

Hydrostatic level measurement is often used for tank level measurement. Hydrostatic level measurement is one type of continuous level measurement.

Hydrostatic pressure sensors are used to measure the level or fill height of liquids. Hydrostatic pressure measurement is suitable for liquid level measurement due to the static pressure effect of non-flowing fluids. This physical principle describes the effect of the gravity of a stationary (i.e. non-flowing) liquid on the measurement point. This gravity is often described as “hydrostatic pressure”.

Related pressure transmitter

**SI-350 Sanitary Pressure Transmitter**

**High Frequency Dynamic Pressure Sensor**

Frequently
Asked
Questions

Nonlinear error: This is a factor that has little effect on the initial error of the pressure sensor. The reason for the error is the physical nonlinearity of the silicon chip, but for sensors with amplifiers, the nonlinearity of the amplifier should also be included, the linearity error curve can be a concave or convex dynamometer.
Offset error: Since the vertical offset of the pressure sensor remains constant over the entire pressure range, the diffusion variation of the converter and laser trim correction will generate offset errors.
Sensitivity error: The magnitude of the error is proportional to the pressure, if the sensitivity of the device is higher than the typical value, the sensitivity error will be an increasing function of the pressure. If the sensitivity is lower than typical, then the sensitivity error will be a decreasing function of pressure. The cause of this error is a change in the diffusion process.
Hysteresis error: In most cases, the hysteresis error of the pressure sensor can be completely ignored. Because the silicon chip has high mechanical stiffness. Typically, only hysteresis errors need to be considered when pressure changes are large.

Four errors of pressure sensors are inevitable. We can only choose high-precision production equipment. Using high technology to reduce these errors, it is also possible to perform error calibration at the factory and try to reduce errors as much as possible. Therefore, you don’t need to pay too much attention when using it, but try to reduce these errors as much as possible.

Extended Reading: MEMS Pressure Sensors

Please note that Pressure Transmitter Calibration is required after the pressure transmitter has been used for a period of time. In order to ensure the accuracy of the quantity.

A pressure transducer often called a pressure transmitter, is a transducer that converts pressure into an analog electrical signal.

Although there are various types of pressure transducers, one of the most common is the strain-gage base transducer.

Pressure applied to the pressure transducer produces a deflection of the diaphragm, which introduces strain to the gages.

The strain will produce an electrical resistance change proportional to the pressure.

Extended reading: Pressure transmitter working principle

Of course, you can install a pressure gauge.

Pressure transmitters can be categorized into four main types:

Gauge Pressure Transmitter.
Absolute Transmitters.
Differential-Pressure Transmitter.
Multivariable Pressure Transmitters.

Extended reading: High accuracy pressure transducers

Flow is an important parameter in industrial production and life. The amount of fluid flowing through a section of a pipe per unit time is called instantaneous flow. Instantaneous flow is divided into volume flow and mass flow. A flow sensor is a sensor that measures the flow of a fluid. Flow sensor is an important instrument in measurement technology, it is widely used in industrial process control, life science and technology, commercial application, military and other fields. In recent years, with the development of science and technology and the development of human needs, flow sensors are also constantly developing.

Extended reading: Digital Flow Meters

In the hydraulic system, the closed-loop control of the force is mainly caused by the pressure sensor.
The working principle of the pressure sensor in the hydraulic system is that the pressure acts directly on the diaphragm of the sensor. Make the diaphragm produce micro-displacement proportional to the medium pressure. Causes the resistance of the sensor to change. And by using an electronic circuit to detect the change, a standard signal corresponding to the pressure is converted and output.

Sino-Inst offers over 50 pressure sensors for fluid measurement. About 50% of these are differential pressure flow meters, 40% is the liquid pressure sensor, and 20% are pressure Level Transmitter.

A wide variety of Fluid Pressure Sensors options are available to you, such as free samples, paid samples.

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

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Influence of Dielectric Constant on Liquid Level Measurement | Radar-Guided Wave Radar Level Meter

Posted on July 24, 2022 by KimGuo11

“Low dielectric constant liquid measurement, not suitable for radar level gauge”. Inadvertently, we hear this all the time. In fact, when I first entered the industry, I thought so too. After a long time and understanding more, I realized that this statement is a bit one-sided. Let’s discuss it in detail.

what is dielectric constant?

The dielectric constant is the main parameter reflecting the dielectric properties or polarization properties of the piezoelectric smart material dielectric under the action of an electrostatic field. Usually denoted by ε.
Different applications of piezoelectric elements have different requirements for the dielectric constant of piezoelectric smart materials.
When the shape and size of the piezoelectric smart material are certain. The dielectric constant ε is determined by measuring the intrinsic capacitance CP of the piezoelectric smart material.

RFQ Level Sensors

Commonly used dielectric constant table

gas	temperature(℃)	Relative dielectric constant	liquid	temperature(℃)	Relative dielectric constant
water vapor	140~150	1.00785	solid ammonia	-90	4.01
gaseous bromine	180	1.0128	solid acetic acid	2	4.1
helium	0	1	paraffin	-5	2.0~2.1
hydrogen	0	1.00026	polystyrene	20	24~2.6
oxygen	0	1.00051	wireless porcelain	16	6~6.5
nitrogen	0	1.00058	UHF porcelain		7~8.5
Argon	0	1.00056	barium dioxide		106
gaseous mercury	400	1.00074	rubber		2~3
Air	0	1	hard rubber		4.3
hydrogen sulfide	0	1.004	Paper		2.5
vacuum	20	1	dry sand		2.5
ether	0	4.335	15% water wet sand		约9
liquid carbon dioxide	20	1.585	wood		2~8
methanol	20	33.7	amber		2.8
Ethanol	16.3	25.7	ice		2.8
water vapor	14	81.5	shellac		3~4
liquid ammonia	-270.8	16.2	Celluloid		3.3
liquid helium	-253	1.058	Glass		4~11
liquid hydrogen	-182	1.22	Yellow phosphorus		4.1
liquid oxygen	-185	1.465	sulfur		4.2
liquid nitrogen	0	2.28	carbon (diamond)		5.5`16.5
liquid chlorine	20	1.9	Mica		6~8
kerosene	20	2~4	granite		7~9
turpentine		2.2	marble		8.3
benzene		2.283	salt		6.2
paint		3.5	Beryllium oxide		7.5
glycerin		45.8

Dielectric constants of common liquids

The relative permittivity of common solvents is at room temperature and the test frequency is 1KHz.

H2O (water) 78.5
HCOOH (formic acid) 58.5
HCON (CH3) 2 (N,N-dimethylformamide) 36.7
CH3OH (methanol) 32.7
C2H5OH (ethanol) 24.5
CH3COCH3 (acetone) 20.7
n-C6H13OH (n-hexanol) 13.3
CH3COOH (acetic acid or acetic acid) 6.15
C6H6 (benzene) 2.28
CCl4 (carbon tetrachloride) 2.24
n-C6H14 (n-hexane) 1.88
n-C4H10 (No. 4 solvent) 1.78

Extended reading: Non contact level measurement

Influence of Dielectric Constant on Guided Wave Radar Level Meter

From the point of view of process conditions, the dielectric constant of the medium to be measured plays a very important role in the measurement of guided wave radar as a known condition.

According to the electrical properties of the dielectric constant, it is roughly divided into three categories: non-polar substances (εr<2.8), weakly polar substances (2.8≤εr≤3.6), polar substances (εr>3.6) .

For liquefied petroleum gas, petroleum, gasoline or other hydrocarbons in petrochemical plants, and petrochemical products, 1.4≤εr≤4.0.
Alcohol, organic solvent, oil-water mixture, etc., 4.0≤εr≤10.0.
Conductive liquids, such as water-based solutions, dilute acids and bases, εr>10.0.

The Guided Wave Radar Level Meter can measure gas/liquid, gas/solid, and liquid/liquid two-phase interfaces.

Ideal for measuring liquid/liquid interfaces, such as oil-water interfaces.

Extended reading: Oil-water interface measurement-Magtech magnetic level indicator

The Guided Wave Radar Level Meter emits low-energy pulsed microwaves that are sent down the probe at the speed of light. At the interface between the probe and the medium, a considerable proportion of microwave energy is reflected back to the transmitter through the probe to receive the first echo signal.

A certain percentage of the pulses will continue down the probe, traversing the upper low dielectric constant medium until it is reflected on the lower medium surface and the transmitter receives the second echo.

To measure the boundary, the minimum thickness of the upper medium is 10-20 cm, so that the echoes of the two liquids can be distinguished. The maximum thickness of the upper dielectric depends on its dielectric constant.

The dielectric constant of the liquid in the upper layer is relatively low, and the difference between the dielectric constants of the upper layer and the lower layer liquid is required to be greater than 10, and the upper layer medium εr<3, the lower layer medium εr>20. Only in this way can the obvious reflection effect be obtained. Both level and interface can be measured simultaneously.

The smaller the dielectric constant of the medium, the greater the amplitude of the reflected signal. For the medium with low dielectric constant (1.2≤εr≤2.5), the guided wave radar level gauge can be selected for powdery or volatile medium.

Some substances hinder or absorb electromagnetic waves in the gas phase, and there are substances in the gas phase that weaken electromagnetic waves. For example, dust, powder (graphite, iron alloy, etc.) with high conductivity, or volatile media. For example, the dielectric constant of liquid ammonia is at room temperature 25 ℃. It is 14.9, which is a conductive medium and can be measured effectively.

The advanced Guided Wave Radar Level Meter is especially suitable for measuring a variety of powders. And liquids with inclined liquid levels caused by vortices.

Because the reflected wave does not depend on a “flat” surface to reflect the echo, microwave safe transmission makes the medium surface condition less affected. Disturbed liquid surface or foam formation, as well as different curved surfaces or furnace outlet will not affect the measurement. Therefore the Guided Wave Radar Level Meter also has a good measurement effect in turbulent situations.

From the perspective of measurement range, the medium with higher dielectric constant has better reflection performance and is suitable for longer measurement range. Guided Wave Radar Level Meter adopts two-wire loop power supply, 24V (DC) or 220V (AC) liquid level transmitter, low energy consumption, and meets the control level process requirements.

Extended Reading: Low Cost Float Level Sensor for Tank Liquid Volume Monitoring

Influence of Dielectric Constant on Radar Level Meter

The Radar Level Meter adopts the principle of transmit-reflection-receive. The antenna of the Radar Level Meter emits electromagnetic waves. These electromagnetic waves are reflected by the surface of the measured object and then received by the antenna. The time from emission to reception of electromagnetic waves is proportional to the distance to the liquid surface.

In the measurement of Radar Level Meter, the measured medium needs to provide sufficient radar reflection signal. In general, the higher the dielectric constant, the stronger the reflected signal. The farther away the target is, the greater the intensity of the reflection is required. In order to have sufficient signal back to the radar transmitter.

When the radar wave reaches the liquid level surface and is reflected. The radar wave will be absorbed and attenuated. When the attenuation is too much, the radar level gauge will not receive enough signal, resulting in inaccurate measurement. This is the dielectric constant of the measured medium. Effects of radar level gauge measurements.

From this point of view, the dielectric constant has an effect on the Radar Level Meter measurement. However, this problem has been well resolved.

The Radar Level Meter can also perform interface measurements, especially on oil-water interfaces.

Principle: When measuring the interface, the part of the pulse that is not reflected on the surface of the upper product will continue down to the surface of the lower product, and then be reflected back.

The requirements for the dielectric constant when the Radar Level Meter measures the interface are as follows:

(1) The dielectric constant of the upper product must be known and must not be changed;
(2) The difference between the dielectric constants of the two products must be greater than 6;
(3) Mainly used in the interface between oil-water liquid and water/water-like liquid with lower dielectric constant of the upper layer (<3) and higher dielectric constant of the lower product (>20).

Extended Reading: What is level transmitter working principle?

Frequently
Asked
Questions

Water is extremely unique in that it has a high dielectric constant (=80). A high dielectric constant suggests that the solvent (in this case, water) has the ability to screen charges. This means that water molecules will surround both anions and cations in a solution, and ultimately, diminish the attraction of the two charges.

Perhaps a Coaxial Probe Guided Wave Radar Level Transmitter can work for your low dielectric constant.

For example, if you place a cation (such as sodium) in water, the positive charge (+) of sodium is able to interact with anions and other molecules. However, because water has such a high dielectric constant, there is a decreasing effect on the interaction between sodium and its counter-ion. This is primarily because the charges interact with the electric dipole of water more than with each other, decreasing the overall interaction. In comparison to water, the interaction between anions and cations is much greater when placed in solvents with lower dielectric constants

Quote from: Wikibooks Structural Biochemistry/Unique Properties/High Dielectric Constant

The dielectric constant of polar liquid dielectrics decreases with increasing voltage frequency. This is because the carrier mobility is enhanced, making it easier to conduct electricity. such as electrolytic capacitors.

Although radar level meters are affected by the dielectric constant of the medium. Ultrasonic level meters are not affected. More about Ultrasonic Level Sensor Applications.

So far there is no sensor that can measure the volume of liquid. Because there are various shapes of liquid containers, such as cylinders, spheres, rectangles, cylinders and squares with hemispherical ends.

The height of the liquid in these containers can be detected by a variety of sensors. According to the shape of the container, the volume and weight of the liquid in the container can be calculated.

For rectangles, cylinders or squares, the volume and weight of the liquid can be calculated directly by multiplying the floor area of the container by the height of the liquid. And the corresponding relationship is linear. The hemispherical cylinder and sphere at both ends can be calculated by definite integral. The law of curvature change is the volume formula of the function. Calculate the volume and weight of the liquid according to the height of the liquid.

Read more about: Monitoring liquid volume solutions

Radar level instruments measure the distance from the transmitter (located at some high point) to the surface of a process material located farther below in much the same way as ultrasonic transmitters – by measuring the time-of-flight of a traveling wave.

A guided wave radar level transmitter is also called a wave-guided radar level sensor. They can measure both levels and the interface between two media. Through probe rod or cable, complete level contact types continuous level measurement. Such as Coaxial Probe Guided Wave Radar Level Transmitter. This is different from ultrasonic level measurement, which is a non-contact measurement. A guided wave radar level transmitter is often used for tank level measurement. Including liquid and solid. Output 4～20mA/HART, so as to measure and control the level during production.

Extended Reading: Guided-wave radar (GWR) level transmitter working principle

Related Level Sensors

**Alternative to VEGAPULS 64-80GHz FMCW Level Radar**

**SIRD-903 26 GHz Radar level Sensor -Dust solid level measurement**

**SIRD-906 Radar Sanitary Level Sensor**

**SIRD-701 Guided Wave Radar Level Sensor**

**SIRD-702 GWR Corrosive Liquid Chemical Level Sensor**

**SIRD-703 GWR Bulk Solids & Powder Solid Level Sensor**

**SIRD-704 Coaxial Probe Guided Wave Radar Level Transmitter**

**SIRD-705 GWR Level Sensor for High Temperature & High Pressure**

Liquid Volume Sensor? Monitors Liquid Volume Solutions

Posted on July 12, 2022 by KimGuo11

Ideally, we should be able to use a liquid volume sensor to directly measure the volume of the liquid in the container. Well, but in fact, there is no mature liquid volume sensor product on the market.

Because there are various shapes of liquid containers. Such as cylinders, spheres, rectangles, cylinders and squares with hemispherical ends.

RFQ

Level Sensors

So why are we talking about liquid volume sensor here? Don’t worry, we don’t have a mature liquid volume sensor. However, we have A dozen ways for liquid level measurement, with different level sensors. Combined with Sino-Inst’s volume recorder. It can collect, display and convert the liquid level of various regular and irregular tanks in the industrial field into the corresponding tank volume. It is suitable for monitoring, controlling and collecting various process parameters.

Featured Level Sensors

**SI-PCM260 Deep Well Water Level Sensor**

**SI-PCM261 Submersible Pressure Transducer**

Level Measurement Technologies

Principle: The principle of the connector. Developed according to the principle of buoyancy and magnetic coupling.

When the liquid level in the container under test rises and falls. The permanent magnet steel in the float is transmitted to the magnetic flip column indicating panel through magnetic coupling. Flip the red and white columns over 180°.

The column turns from white to red when the liquid level rises.
The column turns from red to white when the liquid level drops.

The junction of red and white on the panel is the actual height of the liquid level in the container, so as to realize the liquid level display.

The structure of the float level meter is mainly designed and produced based on the principles of buoyancy and static magnetic field.

The position of the float with a magnet (abbreviated as float) in the measured medium is affected by buoyancy: changes in the liquid level lead to changes in the position of the magnetic float.

The magnet and sensor (reed switch) in the floating ball act to change the number of components (such as fixed-value resistors) connected in series to the circuit, thereby changing the electrical quantity of the instrument circuit system.

That is, the change of the position of the magnetic float causes the change of the electrical quantity.

The liquid level in the container is reflected by detecting the change of the electrical quantity.

It is designed and manufactured using the principle of mechanical balance.

When the liquid level changes, the original mechanical balance will reach a new balance through the movement of the steel belt under the disturbance of the buoyancy of the float.

The liquid level detection device (float) drives the steel belt to move according to the liquid level. The displacement transmission system drives the transmission pin to rotate through the movement of the steel belt. It then acts on the counter to display the liquid level.

The radar level meter is a measuring instrument based on the principle of time travel. The radar wave runs at the speed of light, and the running time can be converted into a level signal by electronic components.

The probe emits high-frequency pulses and propagates along the cable probe. When the pulses meet the surface of the material, they are reflected back and received by the receiver in the instrument. The distance signal is converted into a level signal.

When the sensor of the magnetostrictive level transmitter works, the circuit part of the sensor will excite a pulse current on the waveguide wire. When the current propagates along the waveguide wire, a pulse current magnetic field will be generated around the waveguide wire.

There is a float outside the sensor rod of the magnetostrictive liquid level gauge. This float can move up and down along the rod with the change of the liquid level.

Inside the float there is a set of permanent magnetic rings.

When the magnetic field of the pulse current meets the magnetic field of the magnetic ring generated by the float, the magnetic field around the float changes so that the waveguide wire made of magnetostrictive material generates a torsional wave pulse at the position of the float. The waveguide wire is returned and detected by the detection mechanism.

By measuring the time difference between the pulse current and the torsional wave, the position of the float, that is, the position of the liquid surface, can be accurately determined.

The radio frequency admittance level meter is composed of a sensor and a control instrument. The sensor can be installed on the roof of the warehouse using rod-type, coaxial or cable-type probes.

The pulse card in the sensor can convert the material level change into a pulse signal and send it to the control instrument. After the control instrument is processed and converted into engineering quantity and displayed, it realizes the continuous measurement of the material level.

The working principle of the tuning fork level controller is to make the tuning fork vibrate at a certain resonance frequency through a pair of piezoelectric crystals installed on the tuning fork base.

When the tuning fork is in contact with the measured medium, the frequency and amplitude of the tuning fork will change. These changes are detected, processed and converted into a switching signal by an intelligent circuit.

The glass plate type liquid level meter is connected to the container through the flange to form a communication device, and the height of the liquid level in the container can be directly read through the glass plate.

The pressure level transmitter adopts the principle of static pressure measurement.

When the liquid level transmitter is put into a certain depth in the measured liquid.

At the same time as the pressure on the liquid surface of the sensor, the pressure of the liquid is introduced into the positive pressure chamber of the sensor through the air-conducting stainless steel. Then the atmospheric pressure Po on the liquid surface is connected to the negative pressure chamber of the sensor to offset the Po on the back of the sensor.

The pressure measured by the sensor is: ρ .g.H , and the liquid level depth can be obtained by measuring the pressure P .

Capacitive level meters measure the level of liquid level by measuring changes in capacitance.

It is a metal rod inserted into the liquid container. The metal rod is used as one pole of the capacitor. The wall of the container is used as the other pole of the capacitor.

The medium between the two electrodes is the liquid and the gas above it.

Because the dielectric constant ε1 of the liquid and the dielectric constant ε2 on the liquid surface are different. For example: ε1>ε2.

Then when the liquid level rises, the total dielectric constant value between the two electrodes of the capacitive liquid level gauge increases accordingly and the capacitance increases.

Conversely, when the liquid level drops, the value of ε decreases, and the capacitance also decreases.

Therefore, the capacitive liquid level meter can measure the level of the liquid level through the change of the capacitance between the two electrodes.

The intelligent electric displacer liquid level meter is a liquid level measuring instrument designed according to Archimedes’ law and the principle of magnetic coupling. The instrument can be used to measure the liquid level, boundary level and density, and is responsible for the output of upper and lower limit alarm signals.

It is designed and manufactured using the principle of mechanical balance.

When the liquid level changes, the original mechanical balance will be disturbed by the buoyancy of the float. The new balance will be achieved by the movement of the steel belt (rope).

The liquid level detection device (float) drives the steel belt (rope) to move according to the liquid level. The displacement transmission system drives the on-site indicating device through the movement of the steel belt (rope), and then displays the liquid level on the display device.

The pontoon is submerged in the liquid in the pontoon chamber and is rigidly connected to the torsion tube system. The force on the torsion tube system is the net weight of the pontoon minus the buoyancy on the pontoon. Under the action of this combined force, the torsion tube is twisted by a certain angle.

Changes in the position, density or boundary level of the liquid in the buoyancy chamber cause the buoyancy force of the buoyancy immersed in the liquid to change, so that the twisting angle of the tube also changes.

This change is transmitted to a sensor rigidly connected to the torsion tube. Change the sensor output voltage. Then it is amplified by electronic components and converted into 4-20mA current output.

Displacer level transmitters use microcontrollers and associated electronics to measure process variables. Provides current output. Drive LCD display and provide HART communication capability.

The magnetic-sensitive electronic two-color liquid level meter is made of high-quality stainless steel and imported electronic components.

The display part adopts high-brightness LED two-color light-emitting tube to form a columnar display screen.

Through the red and green changes of the LED light column, the upper and lower limit alarm and control of the liquid level can be realized.

The external liquid level meter is an instrument that measures the liquid level from the outside of the container using the principle of sonar ranging and “micro-vibration analysis” technology.

Two small external level gauge ultrasonic sensors are installed on the bottom of the tank and the other on the side wall of the tank to compensate for density changes.

The signal of the external level meter sensor is converted by the microprocessor and output to the local display or user control system. Can calculate the height of the liquid in the tank and the volume of the liquid in the tank

The hydrostatic level transmitter encapsulates the diffused silicon oil-filled core in a stainless steel shell.

The front protective cap protects the sensor diaphragm. It can also make the liquid contact the diaphragm smoothly. The water wire is sealed with the housing. The ventilation tube is connected to the outside world in the cable. The internal structure is designed to prevent condensation.

Ultrasonic level Sensor is composed of a complete ultrasonic sensor and control circuit.

The ultrasonic wave emitted by the ultrasonic sensor is reflected by the liquid surface. The time required to return is used for calculation.

The temperature influence in the ultrasonic transmission process is corrected by the temperature sensor, which is converted into the distance between the liquid surface and the ultrasonic sensor.

Output 4mA-20mADC analog signal through LCD screen. Realize remote reading of field instruments.

The differential pressure liquid level transmitter is an electrical component that measures the high and low pressure difference, and then converts it into a current signal by the conversion component and transmits it to the control room.

Differential pressure liquid level transmitter is mainly used for liquid level measurement of closed pressure vessels.

The size of the differential pressure also represents the size of the liquid level height.

Use a differential pressure gauge to measure the differential pressure between the gas and liquid phases to know the liquid level.

Liquid Volume Sensor

The height of the liquid in these containers can be detected by a variety of sensors. According to the shape of the container, the volume and weight of the liquid in the container can be calculated.

Extended Reading: Advantages and disadvantages of laser level transmitter

Monitoring liquid volume solutions

Most of our liquid level sensors can output liquid level signals, such as 4-20mA signal, 0-10V signal, RS485 and so on.

However, the liquid level transmitter alone cannot calculate the liquid volume of tanks of different sizes. It’s too complicated. A separate recorder is required to calculate it.

Therefore, the digital display volume meter can collect, display and convert the liquid level of various regular and irregular tanks in the industrial field into the corresponding tank volume. It is suitable for monitoring, controlling and collecting various process parameters.

So, How to measure volume of liquid?

After the liquid level gauge is installed in your tank, Sino-Inst’s volume display controller/recorder can collect, display and convert the liquid level of various regular and irregular tanks on the industrial site into the volume of the corresponding tank . It is suitable for monitoring, controlling and collecting various process parameters.

The volume meter is equipped with volume download software as standard. Form a liquid level volume comparison table. Import volume meter, suitable for volume conversion of various regular or irregular tanks.

The meter is equipped with RS232 communication interface as standard. Connect with the host computer. Through the volume download software, data writing for regular and irregular tanks can be realized. 1000 sets of data can be downloaded.

Volume Recorder

LCD Volume Display Regulator/ Recorder is specifically designed for industrial on-site regular and irregular canned liquid, volume and mass conversion.

It is based on a 32-bit ARM micro-processor and equipped with the secondary meter with high-speed AD and high-capacity storage unit.

The device has empowered by the surface mounting technology, featuring the design of multiple-layered protection and isolation, with a strong anti-interference capability and high reliability.

It has used the embedded operating system with USB data dump function.

The data storage time could reach up to 720 days.

By using U disk and host computer analysis software, one could call and view the historic curve of process variants and relevant historic data from time to time.

It also could match with various liquid sensors, such as ultrasonic liquid level meter. The device has sound anti-theft and anti-damage and other features.

Measurement Input
Input Signal	Current: 0~20mA, 0~10mA, 4~20mA, 0~10mA rooting, 4~20mA rooting
	Input impedance: ≤ 100Ω
	Maximum input current limit: ≤ 30mA
	Voltage: 0~5V, 1~5V, 0~10V (customized), 0~5V rooting, 1~5V rooting,
	Input impedance: ≥ 500KΩ
Output
Output Signal	Analog output: 4~20mA (load resistance ≤ 480Ω), 0~20mA (load resistance ≤ 480Ω), 0~10mA (load resistance ≤ 960Ω), 1~5V (load resistance ≥ 250KΩ), 0~5V (load resistance ≥250KΩ), 0~10 V (load resistance ≥4KΩ) (customized)
	Alarm output: relay control output – AC220V/2A, DC24V/2A (resistive load)
	Feed output: DC24V±1, load current ≤ 50mA
	Communication output: RS485/RS232 communication interface, configurable baud rate of 1200~9600bps, standard MODBUS RTU communication protocol, RS-485 communication distance of up to 1km, and RS-232 communication distance of up to 15m.
General Parameters
Measuring Accuracy		0.2%FS±1d
Setting Mode		Touch-panel-based key setting; password locking of parameter settings; permanent preservation of settings upon power failure.
Display		Backlit 3.5-inch 128*64 high-resolution dot-matrix FSTN LCD
		Support the display of Chinese characters, figures, curves and bar graphs, as well as screen page turning, historical data search and timescale changes of curves etc. through the panel keys
Recording Interval		1, 2, 4, 6, 15, 30, 60, 120, or 240 seconds, nine options available
Storage Length		3 days (with 1-sec interval) – 720 days (with 240-sec interval)
Printing Control		RS-232C printer interface, supporting SP-A40SH series serial printers
Operating Environment		Ambient temperature: 0~50℃; relative humidity: ≤ 85%RH; avoid strongly corrosive gas
Working Power Supply		AC 100~240V (switching power supply), 50/60HZ; DC 20~29V (switching power supply)
Power		≤5W
Structure		-Standard snap-in type

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