Difference in Details: Pressure Transmitter vs Pressure Gauge

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Do you know the difference between Pressure Transmitter vs Pressure Gauge? Pressure transmitters and pressure gauges are industrial process instruments used to measure the pressure of media.
Understanding the difference between Pressure Transmitter vs Pressure Gauge is something we should do before choosing a transmitter and a pressure gauge. Only in this way can we choose suitable products. Here we explain in detail the difference between Pressure Transmitter vs Pressure Gauge.

RFQ Pressure Transmitters
Pressure Transmitter vs Pressure Gauge

Pressure Transmitter

A pressure transmitter in the general sense is mainly composed of three parts: a load cell sensor (also called a pressure sensor), a measurement circuit, and a process connection. It can convert the physical pressure parameters such as gas and liquid felt by the load cell sensor into a standard electrical signal (such as 4~20mADC, etc.). Measurement, indication and process adjustment are carried out by supplying secondary instruments such as indicating and alarming instruments, recorders, and regulators.

A pressure transmitter is an instrument that accepts a pressure variable and converts the pressure change into a standard output signal in a certain proportion after being converted by sensing. The output signal of the transmitter is transmitted to the central control room for pressure indication, recording or control.

Extended Reading: Smart pressure transmitter

In fact, there are many kinds of working principles of pressure transmitters. Commonly used pressure transmitters can be divided into piezoresistive, diffused silicon, ceramic, piezoelectric and capacitive pressure transmitters according to the measurement principle of the pressure sensor.

Here, we use the piezoresistive pressure transmitter to introduce the working principle of the pressure transmitter.

The electrical components of pressure transmitters that sense pressure are generally resistance strain gauges.

The resistance strain gauge is a sensitive device that converts the pressure on the device under test into an electrical signal.

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

Usually, the strain gauges are tightly bonded to the mechanical strain-generating substrate through a special adhesive.

When the stress of the matrix changes. The resistance strain gauge also deforms together. Change the resistance value of the strain gauge. This changes the voltage across the resistor.

Pressure transmitter is the most commonly used sensor in industrial practice, and it is widely used in various industrial automatic control environments.

  1. Petroleum/Petrochemical/Chemical
    • It is matched with the throttling device to provide accurate flow measurement and control.
    • Measures pressure and liquid level in pipes and storage tanks.
  2. Electricity/city gas/other companies
    • Places that require high stability and high precision measurement.
  3. Pulp and paper
    • Used in places that require resistance to chemical liquids, corrosive liquids, etc.
  4. Iron and steel alloys / non-ferrous metals / ceramics
    • It is used in occasions requiring high stability and high precision measurement such as furnace pressure measurement.
    • For use in locations requiring stable measurements under strictly controlled (temperature, humidity, etc.) conditions.
  5. Machinery/Shipbuilding
    • It is used in places where stable measurement is required under strict control (temperature, humidity, etc.) and high-precision conditions.

According to different classification standards, pressure transmitters can be divided into different categories.
For example, depending on the type of pressure being measured. It can be divided into static pressure transmitter, absolute pressure transmitter, differential pressure transmitter and so on.

Commonly used pressure transmitters can be divided into piezoresistive, diffused silicon, ceramic, piezoelectric and capacitive pressure transmitters according to the measurement principle of the pressure sensor.

(1) piezoresistive pressure transmitter

One of the main components of piezoresistive pressure transmitters is the resistance strain gauge. It is a sensitive device that converts the strain change on the DUT into an electrical signal. When the stress of the matrix changes. The resistance strain gauge also deforms together. Change the resistance value of the strain gauge. This changes the voltage across the resistor. The transmitter has extremely low price and high accuracy and good linearity characteristics.

(2) Diffused silicon pressure transmitter

Diffused silicon pressure transmitters utilize the piezoresistive effect of elastic elements. When the pressure of the measured medium acts directly on the diaphragm of the sensor. The diaphragm produces a micro-displacement proportional to the medium pressure. Change the resistance value of the sensor.

Compared with traditional products, this transmitter has the advantages of advanced technology, reliable performance, convenient installation, high accuracy and small size.

(3) Ceramic pressure transmitter

Corrosion-resistant ceramic pressure transmitters have no liquid transfer. When the pressure acts on the ceramic diaphragm. The diaphragm deforms slightly. Make the thick film resistor printed on the back of the ceramic diaphragm pass through the Wheatstone bridge (closed bridge) connected to it. Output a voltage signal proportional to the excitation voltage. The pressure physical quantity is measured through the built-in circuit of the transmitter and converted into a unified standard signal.

The transmitter can introduce various media (corrosive and non-corrosive gases, liquids) directly to the ceramic diaphragm. The thermal stability of the ceramic and its thick-film resistance allow it to operate over a temperature range as high as -40°C to 135°C. Therefore, it has high measurement accuracy, good stability, strong output signal and low price.

(4) Piezoelectric pressure transmitter

Piezoelectric pressure transmitters work on the piezoelectric effect. The crystal is anisotropic, and when a force is applied along a certain direction, the crystal can produce an electric effect. When the mechanical force is removed, it will return to the uncharged state again.

The piezoelectric materials mainly used in sensors are quartz, sodium potassium tartrate and ammonium dihydrogen phosphate. The transmitter is mainly used in the measurement of acceleration and pressure. It has the characteristics of simple structure, small size, light weight and long service life. But it can only be used to measure dynamic stress.

(5) Capacitive pressure transmitter

The capacitive pressure transmitter is composed of a measuring diaphragm and electrodes on both sides of the insulating sheet to form a capacitor. When the pressure on both sides is inconsistent, the displacement of the measuring diaphragm is proportional to the pressure difference. Therefore, the capacitance on both sides is not equal.

Through the oscillation and demodulation link, it is converted into a signal proportional to the pressure. Then the pressure physical quantity is measured and converted into a unified standard signal through the transmission circuit. With its high precision, corrosion resistance, pollution resistance and good stability, it is recognized as an ideal instrument for detecting low vacuum pressure at home and abroad. It is mainly used in various fields of civil industry, and plays a unique role in military industries such as aerospace industry and nuclear industry.

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Pressure Gauge

A pressure gauge refers to an instrument that uses elastic elements as sensitive elements to measure gas, steam, and liquid pressure. It is widely used. It is used in almost all industrial processes and scientific research fields.

The pressure value of gas, steam and liquid measured by the pressure gauge is called gauge pressure.

Gauge pressure is based on standard atmospheric pressure.

Instruments that measure pressure values above standard atmospheric pressure are called positive pressure gauges or pressure gauges.

Instruments that measure pressure values below standard atmospheric pressure are called negative pressure gauges or vacuum pressure gauges.

Instruments that can measure both positive and negative pressures are called pressure vacuum gauges.

It can be seen everywhere in heat pipe network, oil and gas transmission, water and gas supply system and other fields.

Read more about: The Difference Between Absolute And Gauge Pressure

Bourdon tube pressure gauges are also known as Bourdon tube pressure gauges. The free end of the spring in the pressure gauge is closed, and it drives the sector gear to rotate through the pull rod.

During pressure measurement, the spring tube deforms under the measured pressure. Therefore, the free end of the spring tube produces a displacement. The displacement is proportional to the measured pressure. The pointer is deflected and the pressure value is indicated on the dial.

If there is atmosphere in the case, the pressure measured by the pressure gauge is positive or negative;
If the case is sealed and evacuated, the pressure measured by the manometer is absolute pressure.

When the spring tube pressure gauge is equipped with an isolation device, it can still measure the pressure of high temperature or corrosive, viscous, easy to crystallize and dusty media.

In elastic pressure measuring instruments with high precision (such as above grade), the elastic elements are mostly made of constant elastic alloy or even quartz glass.

Jewel bearings or rolling bearings are inlaid in the shaft holes of the transmission mechanism. The dial scale is long, and some can also be displayed digitally.

Pressure gauges have become a part of applications in various industries. They are used in many industries such as machinery, chemical industry, medical treatment, food, petroleum, shipbuilding, electric power, metallurgy, tap water, water treatment, environmental treatment, and power stations.

Simply put, a pressure gauge is based on atmospheric pressure and is used to measure instruments that are less than or greater than atmospheric pressure.

Commonly used pressure gauge uses are as follows.

1, to monitor the working condition of the medium filled inside the pressurized vessel in operation. in order to properly control the pressurized capacity and protect the safety of production equipment.

2, to understand the state of material changes in the production process. So that certain process parameters are controlled under the given conditions to ensure that the quality of the product meets the requirements.

3、By mastering the pressure parameters. To provide reliable data for the operator to monitor, control and regulate production.

According to different uses, pressure gauges can be divided into: diaphragm pressure gauges, stainless steel pressure gauges, ammonia pressure gauges, magnetic-assisted electric contact pressure gauges, shock-resistant pressure gauges, stainless steel diaphragm pressure gauges and many other types of pressure gauges.

The following is a brief introduction one by one:

(1) Stainless steel pressure gauge

Stainless steel pressure gauges are widely used in petroleum, chemical industry, chemical fiber, metallurgy, power station and other industrial sectors to measure the pressure of various fluid media in the process with high requirements for corrosion resistance and vibration resistance.

(2) Ammonia pressure gauge

The ammonia pressure gauge is mainly suitable for measuring the pressure of ammonia liquid, gas or its mixture in the process of fertilizer production or in refrigeration equipment.

It can also be used to measure the pressure of various non-corrosive, non-crystalline and solidified media such as ordinary carbon steel, austenitic stainless steel, platform metal structural steel, and tin brazing materials.

(3) Magnetic-assisted electric contact pressure gauge

Magnetic-assisted electric contact pressure gauges are widely used in petroleum, chemical industry, metallurgy, power stations and other industrial sectors or in supporting mechanical and electrical equipment to measure the pressure of various fluid media without explosion hazard.

Usually, the meter can be used in conjunction with corresponding electrical devices such as relays and contactors to achieve automatic control and send alarms for the measured and controlled pressure system.

(4) Shockproof pressure gauge

It is used to measure the pressure of gases or liquids that are non-corrosive to copper and copper alloys, non-explosive, non-crystallizing, and non-precipitating.

The biggest feature of the shock-resistant pressure gauge is that it can measure pressure normally in a machine tool or equipment that vibrates violently.

(5) Stainless steel bellows pressure gauge

The stainless steel bellows pressure gauge is a corrosion-resistant micro-pressure gauge developed with reference to the structural characteristics of the original bellows pressure gauge.

Applied to equipment such as boiler ventilation and gas pipelines, to measure the micro-pressure and negative pressure of various gas media in processes with high corrosion resistance requirements.

(6) Diaphragm pressure gauge

Diaphragm pressure gauges are suitable for measuring the pressure or negative pressure of various fluid media with certain corrosiveness, non-solidification or non-crystallization. Corrosion resistance depends on the diaphragm material.

Read more about: Calculation Of Pressure Drop

Difference list: Pressure Transmitter vs Pressure Gauge

The difference between a pressure transmitter and a pressure gauge are:

  1. The standard instrument accuracy required for pressure transmitter calibration is much higher than the standard instrument accuracy required for pressure gauges.
  2. The pressure gauge only needs to verify the relationship between a pair of input and output, while the pressure transmitter may need to verify the relationship between input and communication data.
  3. The calibration of the pressure gauge must have the corresponding measurement qualification, and the pressure transmitter is generally not required except for the production plant and new construction.
  4. The precision of the pressure gauge is poor, there is no output, and the manual operator cannot be used. Generally, 5 points are checked, and the back and forth difference is different. The intelligent pressure transmitter generally only needs to calibrate the zero point and full scale.
  5. The output of the pressure gauge is a scale indication, which is displayed by itself. The pressure transmitter is a current output and must be connected to an ammeter of the corresponding accuracy level for display.

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Sino-Inst is a manufacturer of Pressure Transmitter. We offer more than 50 types of Transmitters. Main products include compact pressure transmitters, industrial pressure transmitters, differential pressure transmitters, single crystal silicon pressure transmitters, diffused silicon pressure transmitters , Diaphragm pressure transmitter, high temperature pressure transmitter, explosion-proof pressure transmitter, pressure transmitter, custom pressure transmitter, with remote pressure transmitter, 316 diaphragm pressure transmitter.

Sino-Inst’s Pressure Transmitters are the most commonly used sensors in industrial applications. Widely used in water conservancy and hydropower, railway transportation, intelligent building, production control, aerospace, military industry, petrochemical industry, oil well, electric power, ship, machine tool, pipeline and other industries.

Sino-Inst’s entire team is well trained, so we can ensure that each customer’s needs are met. If you need any help with your product requirements, whether it is a Pressure Transmitter, level sensors, or other equipment, please give us a call.

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About KimGuo11

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.