Before installing and using the pressure transmitter, you should read the product samples and instructions for use in detail. During installation, the pressure interface should not leak, to ensure that the range and wiring are correct. The shell of the pressure sensor and the transmitter generally needs to be grounded. The signal cable should not be laid together with the power cable. Strong electromagnetic interference should be avoided around the sensor and the transmitter. Sensors and transmitters should be periodically verified in accordance with industry regulations during use. Analysis and treatment of common failures of capacitive pressure transmitters. The sensitive parts of capacitive pressure transmitters are all welded, and the electronic circuit parts are wave soldering and connector installation. The overall structure is strong and durable, and there are few failures. For the vast majority of users, if it is found that the sensitive parts are faulty, they generally cannot repair themselves, and they should contact the manufacturer to replace their entire parts.
Checking the transmitter measurement part The faults generated by the transmitter measurement part will cause the transmitter to have no output or abnormal output, so the measurement sensitive parts of the transmitter should be checked first. Remove the flange and check whether the isolation diaphragm of sensitive parts is deformed, damaged or leaked. Remove the compensation plate, do not take out the sensitive parts, check the insulation resistance of the plug. If the voltage does not exceed 100V, the insulation resistance should not be less than 100MΩ. Connect the circuit and the gas circuit. When the pressure signal is 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 means that the transmitter is leaking. Soak the water to check the leak.
Check the circuit part of the transmitter Turn on the power, and after giving the input pressure signal, check the status of the voltage signal at the output of the transmitter. 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 a wiring error between the power supply and the transmitter and the load device. If there is no voltage on the terminal of the transmitter or the polarity is reversed, it can cause the transmitter to output no voltage signal. To eliminate the above reasons, you should further check whether the components in the amplifier board circuit are damaged; if the circuit board connector has bad contact, you can take the method of comparing the measured voltage of the normal instrument with the corresponding measurement voltage of the failed instrument to determine the fault Point, if necessary, replace the faulty amplifier board. When checking the flow type transmitter, special attention should be paid to anti-static measures for the J-type amplifier board.
Turn on the power, after the input pressure signal is given, if the output of the transmitter is too high (greater than 10VDC), or the output is too low (less than 2.0VDC), and there is no response when the input pressure signal is changed and the zero and span screws are adjusted . For this type of fault, in addition to checking whether the sensitive parts of the transmitter measurement part are abnormal, check whether the "oscillation control circuit part" on the transmitter amplifier board is working properly. The normal peak voltage between the high-frequency transformer T1-12 should be 25 ~ 35VP-P; the frequency is about 32kHz. Second, check the working condition of each operational amplifier on the amplifier board; whether the components of each part are damaged or not. Such failures require replacing the amplifier board. The transmitter is very strict in circuit design and process assembly quality. In actual use, it is best to contact the manufacturer to replace the faulty circuit board after inspection and confirmation to ensure the stability of the instrument for long-term work And reliability.
On-site failure inspection Most of the failures on the construction site are caused by improper use and installation of pressure sensors. There are several aspects to sum up. 1. The primary element (orifice plate, remote measurement connector, etc.) is blocked or the installation form is incorrect, and the pressure point is unreasonable. 2. Leakage or blockage of the impulse pipe, residual gas in the filling pipe or residual liquid in the inflation pipe, and deposits in the process flange of the transmitter, forming a measurement dead zone. 3. The wiring of the transmitter is incorrect, the power supply voltage is too high or too low, indicating that the connection between the meter head and the terminal of the instrument is poor. 4. The installation is not strictly in accordance with the technical requirements, and the installation method and site environment do not meet the technical requirements.
The above faults of the pressure sensor and the transmitter will cause abnormal output or inaccurate measurement of the transmitter, but after careful inspection, strict use and installation in accordance with the technical requirements, timely and effective measures are taken, and the problem can be eliminated. Failure, the transmitter should be sent to the laboratory or manufacturer for further inspection.