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A temperature transmitter thermocouple shows fluctuating readings; the signal cable was checked, and the feedback current also fluctuates. Isolating the transmitter, the signal still fluctuates when using a signal generator; the same thing happens even when changing the gauge. Consider whether it is strong electrical interference
The temperature signal enters the DCS display: from thermocouples, transmitters, junction boxes, main cables to cabinet terminal blocks, safety barriers, cards, and controllers. Segmental exclusion (field instruments, cables, systems). 1. The signal also fluctuates when a signal generator is used; the problem persists even after replacing the instrument ； The on-site instruments should be fine ； 2. Disconnect from the site and send a signal to the safety barrier’s input; if there is no fluctuation, it indicates that the system is functioning properly ； 3. Cable inspection: short-circuit resistance, resistance to ground, induced voltage ； 4. Sometimes it may be caused by minor faults, such as loose connections in the wiring. Thoroughly examine every aspect of the entire circuit.
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