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, production automatic 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 unified output signal of electric type is ~ 1ma, 4 ~ 2ma or 1 ~ 5v DC signal. The unified output signal of pneumatic type is gas pressure of 2 ~ 1 Pa.
according to different conversion principles, pressure transmitters can be divided into force (torque) balance type, capacitance type, inductance type, strain type and frequency type, etc. The following briefly introduces the principles, structures, use, maintenance and calibration of several pressure (differential pressure) transmitters. The main function of the pressure transmitter is to transmit the pressure signal to the 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 (4-2mA). The pressure has a linear relationship with the voltage or current, which is generally proportional. Therefore, the voltage or current output by the transmitter increases with the increase of pressure, thus obtaining a relationship between pressure and voltage or current. The two pressures of the measured medium of the pressure transmitter are introduced into the high and low pressure chambers, and the pressure in the low pressure chamber is atmospheric pressure or vacuum, which acts on the isolation diaphragm on both sides of the δ element (that is, the sensitive element) and is transmitted to both sides of the measurement 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 pressure on both sides is inconsistent, the measuring diaphragm is displaced, and the displacement is proportional to the pressure difference, so the capacitance on both sides is unequal. Through oscillation and demodulation.