Pressure transmitter is a kind of equipment that converts pressure into pneumatic signal or electrical signal for control and remote transmission.
It can convert the physical pressure parameters such as gas and liquid sensed by the pressure sensor into standard electrical signals (such as 4~20mADC, etc.). ), which can be provided to secondary instruments such as indicating alarm, recorder and regulator for measurement, indication and process adjustment. Pressure transmitter is the most commonly used sensor in industrial practice, which is widely used in various industrial automatic control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, automatic production control, aerospace, military industry, petrochemical industry, oil wells, electric power, ships, machine tools, pipelines and many other industries. There are two types of pressure transmitters: electric and pneumatic. The electric unified output signal is 0 ~ 10 mA, 4 ~ 20 mA or 1 ~ 5 V DC signal. Pneumatic unified output signal is gas pressure 20 ~ 100 Pa.
According to the different conversion principles, pressure transmitters can be divided into force (torque) balance type, capacitance type, inductance type, strain type and frequency type. The principle, structure, use, maintenance and calibration of several pressure (differential pressure) transmitters are briefly introduced below.
The main function of the pressure transmitter is to transmit the pressure signal to electronic equipment, and then display the pressure on the computer. Its principle is roughly as follows: the mechanical signal of water pressure is converted into the electronic signal of current (4-20mA). Pressure has a linear relationship with voltage or current, and is generally proportional. Therefore, the voltage or current output by the transmitter increases with the increase of pressure, thus obtaining the relationship between pressure and voltage or current. Two pressures of the measured medium of the pressure transmitter are introduced into the high and low pressure cavities, and the pressure in the low pressure cavity is atmospheric pressure or vacuum, which acts on the isolation diaphragms on both sides of the δ element (that is, the sensitive element) and is transmitted to both sides of the measuring diaphragm through the isolation diaphragm and the filling liquid in the element.
The pressure transmitter is a capacitor composed of measuring diaphragm and electrodes on insulating sheets on both sides. When the pressures on both sides are inconsistent, the measuring diaphragm is displaced, and the displacement is proportional to the pressure difference, so the capacitances on both sides are not equal. Through oscillation and demodulation.