Capacitor pressure transmitter faults and precautions
Capacitive pressure transmitters are simple in structure, robust and durable. They have high stability, high precision and good linearity. They have a wide measuring range and are widely used in various industrial automation environments, involving water conservancy and hydropower. Railway traffic, intelligent buildings, aerospace, military, petrochemical, oil wells, electric power, ships, machine tools, pipelines and other industries, this paper analyzes the faults and precautions encountered in the use of pressure transmitters.
Pressure transmitter troubleshooting mainly has the following 4 aspects
1. The primary component (orifice plate, remote measurement connector, etc.) is blocked or installed in the wrong form, and the pressure point is unreasonable.
2. Leakage or blockage of the pressure guiding tube, residual gas in the liquid filling tube or residual liquid in the inflation tube, deposits in the process flange of the transmitter, forming a dead zone.
3. The transmitter wiring is incorrect, the power supply voltage is too high or too low, and the contact between the meter head and the meter terminal is poor.
4. It is not installed in strict accordance with the technical requirements, and the installation method and on-site environment do not meet the technical requirements.
The above faults will cause the transmitter output to be abnormal or the measurement is inaccurate, but after careful inspection, strictly use and install according to the technical requirements, take effective measures in time, the problems can be eliminated, and the faults that cannot be handled should be transmitted. The device is sent to the laboratory or the manufacturer for further inspection.
Key point attention
Special considerations for capacitive pressure transmitters in use.
1. First check whether there is signal interference around the pressure transmitter. If there is, try to eliminate it, or connect the sensor shielding wire to the metal casing as much as possible to enhance the anti-interference ability.
2. Periodically clean the mounting holes to ensure that the mounting holes are clean. Prevent the transmitter from coming into contact with corrosive or overheated media.
3. When wiring, pass the cable through the waterproof connector (accessory) or the winding tube and tighten the sealing nut to prevent rainwater from leaking into the transmitter housing through the cable.
4. When measuring the gas pressure, the pressure tap should be opened at the top of the process pipe, and the transmitter should also be installed in the upper part of the process pipe so that the accumulated liquid can be easily injected into the process pipe.
5. When measuring the liquid pressure, the pressure tap should be opened on the side of the process pipe to avoid sedimentation.
6. The voltage above 36V cannot be used on the pressure transmitter, which is easy to cause damage.
7. When freezing occurs in winter, the transmitter installed outside must adopt anti-freezing measures to prevent the liquid in the pressure inlet from expanding due to the volume of ice, leading to damage to the sensor.
8. When measuring steam or other high-temperature medium, it is necessary to add a condenser such as a buffer tube (coil), and the operating temperature of the transmitter should not exceed the limit. Moreover, the buffer tube needs to be filled with an appropriate amount of water to prevent the superheated steam from coming into contact with the transmitter. Moreover, the buffer heat pipe cannot leak air.
9. When measuring the liquid pressure, the installation position of the transmitter should avoid the impact of liquid (water hammer phenomenon), so as to avoid damage of the sensor over pressure.
10. The pressure guiding pipe should be installed in a place with small temperature fluctuations.
11. Prevent dross from depositing in the conduit.
12. The medium measured by the capacitive pressure transmitter cannot be frozen and frozen. Once it is frozen, it will easily damage the diaphragm because the diaphragm is generally thin.