Pressure sensors are one of the most commonly used sensors in industry, because just as blood pressure is an important data for a person's health, pressure values are as indispensable for industrial production. Its widely used in a variety of industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent construction, production self-control, aerospace, military, petrochemical, oil well, electric power, ship, machine tools, pipelines and many other industries.

Pressure sensors are usually used to measure the pressure of gases and liquids (actually called pressure sensors are more accurate, but we have all agreed on it)

Because of the pressure measured, pressure sensors are generally measured in Pascals, i.e. Newtons per square metre, as Pascals are too small and it is more common to use Bar and PSI pounds per square inch. Atm on the other hand is a standard atmospheric pressure.

1psi = 1lbf/(1in)² ≈ 4.4482N/(0.0254m)² ≈ 6894.757N/m² ≈ 6894.757Pa

Or you can convert 1 standard atmosphere (atm) to approximately 14.7 pounds of force per square inch (psi)

1atm=101325Pa=101329Pa/(6894.757293168Pa/psi)≈14.696psi

Friends may see this atm and PSI units more commonly in a tyre pressure gauge, and yes, a tyre pressure gauge is a pressure sensor.

Pressure sensor applications

In industry, pressure sensors are used in a variety of processes. The most common use is to measure steam pressure. Steam is often used for process heating, and boilers are the most important equipment for generating steam. Pressure sensors on boiler systems can be used for a variety of purposes.

The first and most obvious is to observe and monitor pressure, which is used as an important basis for releasing steam and regulating its pressure. Steam can build up pressure in vessels and become dangerous (e.g. autoclaves). We can use pressure sensors as input devices to open and close control valves to maintain pressure and steam flow regulation. This can be achieved with simple programming in a PLC.

In many industrial processes, the pressure sensor is also installed next to the filter. The specific process is that if the filter starts to clog, the flow rate will decrease. As the liquid flow decreases, the pressure can increase or decrease depending on which side of the filter is being monitored. The pressure is used to determine whether the filter is clogged and whether it needs cleaning or replacement.

A special point of use is the use of a pressure sensor as a level sensor.

In an open tank, the pressure obtained from the measurement can be used to calculate the level height by a simple calculation in which the specific gravity of the liquid is known, and then the volume of the tank is known to determine how much liquid is present.

If the tank is airtight, such as a boiler, the differential pressure has to be measured by a differential pressure sensor in order to calculate the level height. The installation would be more cumbersome, but it is still a viable option.

How to choose a pressure sensor

As there are different types of pressure (absolute, differential, gauge), it is important to understand the factors that can affect the use of the sensor. It is important to know whether the contact to the sensor is a liquid or a gas and whether it is corrosive. The application of a sensor for fluid measurement is different from that of an ordinary sensor when the fluid to be measured has the potential to damage the sensor. Other important factors are the measuring range (expressed in bar, psi, Atm, etc.). The range of pressure that can be measured by the sensor while maintaining the accuracy required by the measurement specification. And whether the measuring range is unipolar (pressure or vacuum) or bipolar. For example, to measure a pressure value below atmospheric (evaporation tower), a gauge pressure sensor would result in a negative value, which would cause problems in both calculation and control. In this case it is much easier to use an absolute pressure sensor.

In addition the "over pressure" or "proof pre-ssure" (the maximum pressure at which the sensor can be accepted without incurring damage) is important in the selection of the sensor. It is also important to know the operating temperature range. The temperature of the liquid or gaseous substance to be measured must not exceed the operating temperature range of the sensor.