The capacitive pressure transmitter measures all sensitive parts in the all-welded structure. Wave soldering and connector mounting are used in the electronic circuit. The overall structure is sturdy and durable, with few failures. For the vast majority of users, if it is found that a sensitive part is malfunctioning, it cannot generally be repaired on its own. Contact the manufacturer to replace its entire parts.
First, the pressure transmitter measurement part of the inspection
Failure of the measuring part of the pressure transmitter will cause the pressure transmitter to have no output or an abnormal output. Therefore, the pressure transmitter's measurement-sensitive components should be checked first.
1 . Remove the flange and inspect the isolation diaphragm of sensitive parts for deformation, breakage and oil leakage.
2 . Remove the compensation plate, do not take out the sensitive parts, check the insulation resistance of the plug- in case, and the insulation resistance should not be less than 100MΩ when the voltage does not exceed 100V .
3 . Turn on the circuit and gas circuit. When the pressure signal is the upper limit of the range, turn off the gas source , and the output voltage and reading value should be stable. If the output voltage drops, there is a leak in the pressure transmitter. Check for leaks with soapy water.
Second, the pressure transmitter circuit part of the inspection
1 . Turn on the power and check the status of the voltage signal at the output of the pressure 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; whether there is any wiring error between the power supply and the pressure transmitter and the load device. If there is no voltage or reversed polarity on the pressure transmitter terminal, the pressure transmitter will have no voltage signal output. Exclude the above reasons, you should further check the amplifier board circuit components for damage problems; circuit board connectors have no contact with the phenomenon of bad, can be measured against the normal instrument measurement voltage and fault meter corresponding to the measured voltage compared to the method to determine the failure Point, if necessary, replace the faulty amplifier board. When checking flow-type pressure transmitters, special attention should be paid to J -type amplifier boards to prevent static electricity.
2 . Turn on the power, if the pressure transmitter output is too high ( more than 10VDC) , or the output is too low ( less than 2.0VDC) after the input pressure signal is given, and the output is not changed when the input pressure signal is changed and the zero point is adjusted and the range screw is reaction. For such failures, in addition to checking whether there are any abnormalities in the sensitive parts of the pressure transmitter measurement part, check whether the “ oscillation control circuit part †on the pressure transmitter amplifier board is working properly or not. The normal peak voltage between high-frequency transformer T1-12 should be 25~35VP-P ; the frequency is about 32kHz . Secondly, check the operational status of each operational amplifier on the amplifier board; whether the components of each part are damaged or not. This type of fault requires the replacement of the amplifier board.
3 . The pressure transmitter has very strict requirements on circuit design and process assembly quality. In actual use, the line fault occurs. After checking and confirming, contact the manufacturer to replace the faulty circuit board to ensure the stability of the instrument's long-term operation. reliability.
Third, on-site failure to check the failure of the construction site
The vast majority are due to improper use and installation methods. There are several aspects to sum up.
1 . The primary component ( orifice plate, remote measurement connector, etc. ) is blocked or improperly installed, and the pressure point is unreasonable.
2 . Leakage or blockage of the pressure pipe, residual gas in the filling pipe or residual liquid in the aeration pipe, deposits in the process flange of the pressure transmitter, forming a measurement dead zone. 3 . The pressure transmitter wiring is not correct, the power supply voltage is too high or too low, indicating poor contact between the meter header and the meter terminal block connections.
4 . The installation was not strictly in accordance with the technical requirements, and the installation method and the on-site environment did not meet the technical requirements. The above failures will cause the pressure transmitter to output abnormally or inaccurate measurements, but after careful inspection, strictly follow the technical requirements to use and install, take effective measures in time, the problem can be ruled out, the pressure on the failure can not be handled, the pressure should be The transmitter is sent to the lab or manufacturer for further inspection.
Gas Isothermal Normalizing Furnace
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