Pressure transmitter is an instrument that converts pressure signal into a usable standardized output signal, and there is a given continuous function relationship (usually a linear function) between the output signal and the pressure variable. It is widely used in industrial sites due to its reliable operation, high accuracy, stable performance, strong anti-interference ability and long transmission distance of measurement signals. Its standardized output signals are mainly (0~10)mA, (4~20)mA and (1~5)V DC signals. According to different pressure measurement types, it can be divided into positive (negative) pressure transmitters, differential pressure transmitters, absolute pressure transmitters, etc.
Pressure transmitters are bound to have various faults during use, which are affected by many factors, such as filling liquid leakage between the diaphragm and the sensor element in the pressure transmitter, zero point and range offset, unstable output, etc., which will cause the pressure transmitter to lose accuracy or even be damaged; weather factors will also affect the transmitter, such as lightning strikes will damage the circuit of the transmitter diaphragm box, resulting in communication failure; humid environment will damage the line; unreasonable selection of transmitter range will cause irreversible deformation of the pressure sensing element. The following are several common types of faults:
(1) Line failure
When a line failure occurs, the computer displays abnormal values. Open the junction box of the pressure transmitter and check whether the line is virtual, short-circuited or disconnected. Then use methods such as measuring power supply, shaking insulation and measuring resistance to troubleshoot the fault.
(2) Frequency conversion interference
When wiring, multiple signal lines interfere with each other, especially when the power line and signal line are strung in the same pipeline. In this case, the pressure transmitter will not communicate or even cause errors. Such erroneous operations can be avoided by increasing the distance between the instrument cable and the power cable tray.
(3) Pressure lead pipe failure
There are usually three types of failures in the pressure lead pipe: blockage, leakage and accumulation of liquid in the pressure lead pipe:
1) Pressure lead blockage is generally caused by untimely discharge or dirty or sticky medium;
2) Leakage of the pressure lead pipe is caused by the fact that the pressure transmitter has too many accessories such as power connection and stop valve, which increases the leakage point;
3) Liquid accumulation in the pressure lead pipe is usually caused by unreasonable gas pressure collection method or incorrect installation of the pressure lead pipe. Liquid accumulation in the pressure lead pipe will affect the measurement accuracy.
(4) Electrical signal transmission failure
If the pressure transmitter is not used or maintained properly, it is very easy to cause electrical signal transmission failure. For example, in order to save space, the pressure transmitter is placed near the device under test, resulting in the signal transmission distance being too long, and the signal will be interfered or attenuated. At this time, the cross-sectional area of the cable should be increased as needed.