In the modern industrial automation control system, pressure transducer used in the need for monitoring section, or as a feedback signal of the signal collection of process monitoring regulation effect, achieve the safe and orderly management and control.
Because the characteristics of medium, the different application conditions, we should combine pressure transmitter measuring principle and field application to the analysis of the failure of pressure transmitter and reasons, find a practical and effective solution, do from the selection to installation, from the application to the rationality of the maintenance, and efficient to solve the problem.
Principle of measurement of the pressure transmitter is not the focus of this article, the only on the working principle of pressure transmitter and classification are briefly introduced.
In simple terms, is the use of sensors, pressure transmitter demodulator, current detector, amplifier and so on, will pressure the change of the signals into the standardization of controller can read, 4 ~ 20 ma DC current signal is given priority to, also have 1 ~ 5 VDC voltage signals or communications, etc.
The type of pressure transmitter, pressure can be divided into: (1) simple resistance transmitter, mainly by the semiconductor pressure sensitive material in compression, due to the piezoresistive effect of pressure-sensitive resistance, resistivity changes, make the bridge produces a voltage signal is proportional to the pressure, which measured the change of pressure.
(2) the capacitive transducer, is the use of measuring diaphragm and on both sides of the insulation on the electrodes of a capacitor, two pressure measured medium by high and low pressure chamber, the effect on both sides of the sensitive element isolation diaphragm, diaphragm can produce displacement, according to different pressure on both sides of the capacitance changes, changes the capacitance value will be turned into the controller by oscillation settlement signals can be read.
(3) the inductance pressure transmitter, generally consists of a pointer type pressure gauge and electronic remote transmission parts.
When the pressure gauge spring tube deformation occurs, the iron core displacement will occur inside the inductance coil, inductance changes, the change value is converted into dc current/voltage signal.
(4) the strain type pressure transmitter, is converted to electricity by using pressure resistance to measure.
The two pieces of strain gauge with special cement respectively along the axial and radial sticky on the strain tube, when strain tube due to compression, the resistance strain will appear the shape change, which affect the size of the resistance, and the principle of measurement of the pressure resistance type difference lies in the shape of the strain type transducer can cause strain material change.
