How Do Pressure Sensors Work?

How Do Pressure Sensors Work?

Pressure sensors are extensively used in various applications on a daily basis. Right from medical applications like measuring blood pressure accurately to refrigeration and hydraulic systems to industrial applications to automated building applications, pressure sensors are used to measure pressure or other variables like altitude, speed of fluid or gas flow, pressure difference, calibration, among other parameters.

What are the main components that make up pressure sensors?

Pressure sensors are used to measure the pressure in gases or liquids and convert it into an electrical output signal. The main components of a pressure sensor consist of a pressure-sensitive element and an electronic component. The pressure sensors are used to detect, measure, or monitor the pressure applied while the electronic components convert the information into an electrical output signal.

How do pressure sensors mechanically work?

The pressure sensing element has four strain gauges or diaphragms that change to the same extent when pressure is applied. The electrical resistance that results from the pressure can be measured. When the pressure or strain is high, the electrical resistance will also be on the higher side. Strain gauges are electrical conductors that are placed over a polyimide film in a zigzag shape.

When pressure or any force pulls the polyimide film, the conductors stretch and the resistance increases. On the other hand, when the conductor is pushed, it gets shorter and the resistance decreases. 

What are the types of pressure sensors?

Pressure sensors can be classified based on the type of pressure measurements and pressure-sensing technology. The three common methods to measure pressure are:

Differential pressure sensor: This sensor is used to measure the difference in pressure between two pressure points is known as a differential pressure sensor. Here, only the pressure difference between two points is taken into consideration, while their magnitude relative to atmospheric pressure or to another reference pressure such as absolute vacuum is not. This method is used to measure the flow of a liquid or gas in pipes.

Absolute or vacuum pressure sensor: As the name suggests, the absolute or vacuum pressure sensor is used to measure the absolute pressure. The absolute pressure is the pressure measured in comparison to a sealed vacuum where a constant reference is essential. A few applications where absolute pressure sensors are used are liquid pressure measurement, aerospace and aviation inspection and barometric measurements for weather or in altimeters.

Gauge pressure sensor: Gauge pressure sensors work on the same principle as the differential pressure sensor, however, though the pressures are measured differentially, it is always relative to the local ambient pressure. 

Pressure sensing technologies

Let us take a look at a few pressure-sensing technologies:

 

Resistive: Resistive pressure sensors use a strain gauge bonded to a diaphragm that is exposed to the pressure medium to measure the change in electrical resistance.

Capacitive: Capacitive sensors have a diaphragm that gets deflected when there is pressure. The external pressure compresses the diaphragm, reducing the capacitance value.

Piezoelectric effect: When a piezoelectric material is subjected to mechanical stress or strain, an electrical potential is generated on its surface.

Pressure sensors are required in a variety of applications because they are empowering both businesses and consumers alike towards a smart and safe environment.

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