Capacitive, Strain Gauge, Piezoresistive: Understand The Working Principles Of Different Types Of Pressure Transmitters

Pressure transmitter principle is a sensor used to convert pressure signals into standard signal output. It is widely used in various industrial fields, such as petroleum, chemical industry, steel, electric power, light industry and environmental protection, etc., for measuring and controlling pressure. The working principle and main types of pressure transmitters are introduced as follows:

The working principle of Capacitive pressure transmitter is to convert pressure signals into electrical signals. When the two pressures of the measured medium act on the high and low pressure chambers respectively, they act on both sides of the sensitive element (such as the isolation diaphragm), and are transmitted to both sides of the measuring diaphragm through the isolation plate and the filling liquid in the element. . The Capacitive pressure transmitter consists of two capacitors composed of a measuring diaphragm and electrodes on both sides of the insulating sheets. When the pressure on both sides is inconsistent, the sensitive element will be displaced, and the displacement is proportional to the pressure difference, resulting in different capacitances of the capacitors on both sides. Through oscillation and demodulation links, this displacement is converted into a signal proportional to the pressure.

The working principle of the strain gauge pressure sensor is based on the strain effect of conductors and semiconductors, that is, when the material undergoes mechanical deformation (such as elongation or compression), its resistance value will change accordingly. Strain gauge pressure sensors measure pressure indirectly by measuring the strain of an elastic element such as a wire. The resistance strain gauge is a sensitive device that converts the pressure on the measured piece into an electrical signal. There are two types of metal resistance strain gauges: filament strain gauges and metal foil strain gauges.

The working principle of the Piezoresistive pressure sensor is made by utilizing the piezoresistive effect of single crystal silicon material and integrated circuit technology. When pressure acts on the pressure chamber, the pressure in the pressure chamber will cause slight deformation of the silicon material, thereby changing its resistance value. This change in resistance value is converted into a signal proportional to the pressure.

In addition, the main function of the pressure transmitter is to convert the pressure signal into a standard signal output, such as a 4~20mA current signal, so that the pressure can be displayed and controlled on electronic devices. There is a linear relationship between pressure and voltage or current, usually a proportional relationship.