VI
Common faults and handling methods of pressure transmitters
Release Time:
2023-06-12
The sensitive components of the capacitive pressure transmitter measurement section adopt a fully welded structure, while the electronic circuit section adopts wave soldering and connector installation methods. The overall structure is sturdy and durable, with few faults. Compared to the vast majority of users, if sensitive components are found to malfunction, they are generally unable to repair themselves. Therefore, the manufacturer should be contacted to replace the entire component.
1. Inspection of the measuring part of the transmitter
Analysis: Any fault caused by the measurement part of the transmitter can cause the transmitter to have no output or abnormal output. Therefore, the sensitive components of the transmitter should be checked first.
Handling method:
① Remove the flange and inspect the sensitive component isolation diaphragm for deformation, damage, and oil leakage.
② Remove the compensation board without removing sensitive components. Check the insulation resistance of the contact pin to the housing. When the voltage does not exceed 100V, the insulation resistance should not be less than 100M Ω.
③ Connect the circuit and gas circuit, and when the pressure signal is at the upper limit of the range, turn off the gas source. The output voltage and reading value should be stable. If the output voltage drops, it indicates a leak in the transmitter. Soap water can be used to check the leak location.
2. Inspection of the transmitter circuit
① Connect the power supply and check the status of the voltage signal at the output end of the transmitter after giving the input pressure signal. If there is no output voltage, first check whether the power supply voltage is normal; Whether it meets the power supply requirements; Check for any wiring errors between the power supply, transmitter, and load equipment. If there is no voltage or polarity reversal on the transmitter wiring terminal, it can cause the transmitter to output no voltage signal.
To eliminate the above reasons, further inspection of the components in the amplifier board circuit should be carried out for any damage issues; If there is any poor contact phenomenon in the circuit board connector, the method of comparing the measured voltage of the normal instrument with the corresponding measured voltage of the faulty instrument can be used to determine the fault point. If necessary, the faulty amplifier board can be replaced. When inspecting flow type transmitters, special attention should be paid to taking anti-static measures for the J-type amplifier board.
② Turn on the power supply, and after giving the input pressure signal, if the transmitter output is too high (greater than 10VDC) or too low (less than 2.0VDC), and the output does not respond when changing the input pressure signal and adjusting the zero and range screws.
For such faults, in addition to checking for any abnormalities in the sensitive components of the transmitter measurement section, it is necessary to check whether the "oscillation control circuit section" on the transmitter amplifier board is working properly. The normal peak voltage between high-frequency transformers T1-12 should be 25-35VP-P; The frequency is approximately 32kHz. Secondly, check the working condition of each operational amplifier on the amplifier board; Check if there are any damage issues with the components of each part. This type of fault requires replacing the amplifier board.
③ The requirements for circuit design and process assembly quality of the transmitter are very strict. In practical use, if any circuit faults occur, after inspection and confirmation, contact the manufacturer to replace the faulty circuit board to ensure the stability and reliability of the instrument's long-term operation.
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