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Working principle and common fault analysis of differential pressure transmitter

Release time:2019-06-16

Working principle and common fault analysis of differential pressure transmitter

The working principle and common fault analysis of differential pressure transmitter are more widely used in the industrial automation production, and more and more problems are encountered in production. The analysis and treatment of the fault in time is very important to the production. This paper introduces the experience and fault diagnosis analysis methods in daily maintenance for reference. The working principle of differential pressure transmitter
The differential pressure from the bilateral guide tube directly acts on the diaphragm of the transmitter sensor. Through the seal in the diaphragm, the differential pressure is transferred to the continents element, and the measured differential pressure signal is transferred to the corresponding signal to the converter, and the amplification and other processing become the standard electrical signal output. Several applications of differential pressure transmitters are used in the most ways:
1., combined with throttling elements, the liquid flow is measured by the differential pressure generated by the throttling element. The figure is shown in Figure L. 2. the pressure difference produced by the gravity of the liquid is measured by the height of the liquid, as shown in Figure 2. 3. directly measure the pressure difference between different pipes and liquids.
Two, fault diagnosis method of differential pressure transmitter
In addition to reviewing the situation of fire, smoke, odor, power supply change, lightning, damp, misoperation and maintenance, as well as the external damage of the observation loop, the leakage of the guide tube, the overheating of the loop, the state of the power supply switch and so on, the fault should be diagnosed by detection.
1. open circuit check side: part of the suspected fault is separated from other parts to see if the fault is gone. If it is gone, it can be sure that the fault is here. Otherwise, the next step can be found. For example, the intelligent differential pressure transmitter can not normally communicate with Ha, and can disconnect the power from the instrument body.
The method of adding power to the field is used to communicate with the transmitter to check whether the electromagnetic signals of the Zk - HZ stack are superimposed and interfere with the communication.
2. short connection detection: in the case of security, the relevant part of the circuit is directly connected, for example, the output value of the differential pressure transmitter is small, the pressure tube can be disconnected and the differential pressure signal is directly bow l to the differential pressure transmitter from the pressure valve, and the transmitter output is observed to judge whether the pipeline has no plugging, leakage and connectivity.
3. replace detection: replace the part suspected of malfunction and determine the fault locations. For example, if there is a fault in the transmitter circuit board, one piece can be temporarily replaced to determine the cause.
The 4. part inspection side: divide the circuit of the test dish into several parts (such as power supply, signal output, signal transmission, signal detection), and check each part separately from simple to complex, from the table to the inside, to narrow the range, find out the fault locations. Three. Common troubleshooting
1. possible causes and solutions to the oversize of the output:
(L) a pressure tube. Check the leakage or blockage of the guide pipe; check whether the shutoff valve is open; check if there is any liquid in the gas guide tube or whether there is gas in the liquid guide tube; check whether there is any sediment in the pressure chamber of the transmitter.
(2) the electrical connection of the transmitter. Check the connection of the sensor components of the transmitter. Ensure the contact point of the connector is clean; check whether the 8 pin is reliable enough to connect the watch case.
(3) fault of transmitter circuit. Replace the circuit boards with alternate circuit boards, check the defective circuit boards and replace the defective circuit boards.
(4) check whether the output of the power supply is in line with the required voltage value. 2. possible reasons and solutions for output too small or no output:
(1) the guide tube. Check whether the pipe is leaking or blocking; check whether there is gas in the liquid guide tube; check whether there is any sediment in the transmitter pressure chamber; check whether the shut-off valve is open, and the balance valve is closed.
(2) the electrical connection of the transmitter. Check whether the lead line of the transducer sensor component is short or not; check whether the number 8 pin is reliably connected to the surface; ensure the contact area of the connector is clean; check whether the screws are in the control range.
(3) wiring circuit. Check whether the voltage added to the transmitter is normal; check whether the circuit is short circuit or multi point grounding. (4) fault of transmitter circuit. In addition, alternate circuit boards can be used to replace malfunctioning circuit boards or replace defective circuit boards.
3. possible causes of output instability and solutions:
(L) wiring circuit. Check whether there is intermittent short-circuit, open circuit or multi point grounding phenomenon; check whether the voltage added to the transmitter is suitable.
(2) the measured liquid fluctuates. Adjust the size of the damping action of the circuit.
(3) check whether there is a liquid break in the gas pressure pipe and whether there is gas in the liquid pressure pipe. (4) ensure that the contact area of the connector is clean and check the grounding condition of the sensor assembly.
(5) replace the defective transmitter circuit board with the standby circuit board to judge the fault and replace the defective circuit board. Due to the similarities and differences in the application of differential pressure transmitter and pressure transmitter, some of the methods in this paper also apply to the fault diagnosis of dry pressure transmitter.