What is Pressure Sensor? Structure and principle of operation

A pressure sensor is a specialized device used to measure the pressure and pressure information of air, steam and liquids. Although widely used in many different fields, not everyone has a good understanding of the structure and working principle of the device. So, in the article below, RX Tradex will introduce pressure sensors, their construction and principle of operation.

1. What is a pressure sensor?

A pressure sensor is a type of sensor device designed to measure pressure and pressure information in gas, steam, gas, or liquid tanks. This device is also known by many other names such as pressure probe, manometer, pressure indicator, or pressure transmitter,…

As an electronic device, the pressure sensor is capable of monitoring and monitoring the pressure at the above locations to convert it into a signal transmitted to the display screen, the controller in the form of an electrical signal from 4 to 20mA

2. Structure and working principle of pressure sensor

2.1 Structure of the pressure sensor

The pressure sensor is composed of 2 main parts: the sensor part and the processing block part.

Sensor: This is the part that will receive the signal from the pressure of the gas, steam or liquid to transmit to the process block. Depending on the type of pressure sensor, the mechanical signal of the pressure will be converted into different types of signals such as resistance, inductance, capacitance or current,…

Processing Block Section: This unit receives signals from the sensor section and converts them into standard signal forms in pressure measurement such as 4~20mA, 0~5VDC, 0~10VDC, or 1~5VDC voltage output signals.

2.2 Principle of operation

The pressure sensor converts the pressure into an electrical signal, which then transmits and displays. The two common forms of signals used are current signals with a magnitude of 4 to 20mA and voltage signals from 0 to 5V.

Most pressure sensors work on the use of the piezoelectric effect, which means that the material will generate an electric charge in response to stress. This stress is usually pressure, but can also twist, bend or vibrate. Inside the sensor there is a ceramic membrane, and when pressure is applied to the membrane surface, the sensor membrane changes. The processor then calculates the pressure value based on the deformation of the membrane and outputs a signal. Therefore, the sensor needs to be calibrated so that the voltage or current (mA) signal corresponds to which pressure level.

3. Pressure Sensor Classification

Pressure sensors can be classified based on the pressure range they measure, the operating temperature range, and most importantly, the type of pressure they measure. While it can be called by a variety of names depending on the purpose, the same technology can be used under different names.

Relative Pressure Sensor

Relative pressure sensors work on the principle of comparison with air pressure. When the pressure sensor is placed in an atmospheric environment, the measured pressure will be 0 bar. For example, if the relative pressure is 1 bar, it means that the pressure at the point of measurement is 1 bar higher than the atmospheric pressure.

Absolute Pressure Sensor

The absolute pressure sensor works based on the principle in the sensor that is compressed 1 bar into the sensor. When the sensor is placed in an atmospheric environment, the measured pressure will be 1 bar. For example, if in an air environment there is an acting force with a value of 1 bar, the absolute pressure sensor will measure a value of 2 bar.

Differential Pressure Sensor

This sensor measures the difference between two pressures, with each pressure connected to one side of the sensor. Differential pressure sensors are often used to determine characteristics such as pressure drop through an oil or air filter, fluid level (comparing pressure above and below the surface of the liquid), or flow rate (measuring the change in pressure over a cut-off point).

Technically, most pressure sensors are actually differential pressure sensors. For example, a relative pressure sensor is essentially a differential pressure sensor with one side open to the surrounding air.

4. Application number of pressure sensors

Currently, pressure probes are widely used in many fields, especially in industrial plants. Here are some specific applications:

• Sensors measure hydraulic pressure, compressed air, water, gas pressure, and other liquids…
• In boiler systems, pressure sensors are often installed directly to measure pressure. This area requires high measurement accuracy and high heat resistance.
• Air compressors need to measure pressure to limit the output pressure, preventing overpressure with the risk of damage and explosion. At water pumping stations, it is also necessary to monitor pressure sensors and bring them back to PLC or inverter to control water pumps effectively.
• The pressure sensor plays an important role in regulating the pressure behind the control valve, which directly affects the output pressure.
• On cranes, hydraulic wharves are often closely monitored because they directly affect the traction of the cranes.

5. Instructions for choosing and purchasing the right industrial pressure sensor

There are many types of pressure sensors with diverse origins, functions, and various price segments. However, choosing how to buy an industrial pressure sensor to suit practical systems is not easy. First, it is necessary to learn the following factors:

• Determine the need for pressure sensors in which systems
• Determines the range of pressure to be measured, including the minimum and maximum pressure measured by the sensor
• Determine the type of pressure to be measured, including static, dynamic, or differential pressure
• Consider the level of accuracy required to ensure that measurement requirements are met
• Choose a sensor with a suitable output signal such as 4-20mA or 0-10V, 0-5V (depending on the controller)
• It is necessary to find out the thread of the sensor, as each measurement medium will have different connection threads. As standard connection threads: G1/4 G1/2″, NPT 1/2, NPT 1/4. As for the environment such as food and medicine, it is the Clamp type.

6. Conclusion

Above is the information about pressure sensor that RX Tradex wants to share from the concept, structure to the operating principle of this device, Hopefully through the article, you will have a clearer view of the types of pressure sensors as well as how to choose the right equipment for your needs. In addition, if you are interested in modern automation solutions or want to keep up with the latest trends in the electronics manufacturing industry, participate in NEPCON Vietnam – the only exhibition in Vietnam on SMT technology, inspection technology, equipment and supporting industries for electronics manufacturing, etc  organized by RX Tradex Vietnam. Register right here.