Does the pressure switch require one wire to be disconnected for verification?
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The pressure switch is connected to a relay, which in turn is connected to the PLC. The pressure switch has both normally open and normally closed contacts
The checksum has nothing to do with unplugging the wires, right? If you go back to the calibration lab, you need to unplug all the wires as well as remove the switches:L
Generally speaking, to test a pressure switch, it is best to disconnect all the wires, apply pressure to the switch, and directly check the condition of its contacts – this is the most reliable method. Because if the connection is established, it’s possible that the resistance you measure is that of the DCS/PLC or SIS side, and it’s also possible that there is a short circuit in the wires, which could result in the measurement of resistance; this can easily lead to incorrect judgments.
It’s best to disconnect one; it doesn’t need to be related to DCS or PLC. Then use the tester to apply pressure and simply check for continuity
Verification has nothing to do with the PLC, but for the safety of the PLC, it is better to disconnect the wires. When the pressure reaches that set value, you can measure it with a multimeter.
Is LZ a verification circuit or a meter? To verify the meter, it needs to be removed and taken to a test bench