Thermocouple thermometer failure
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The thermocouple thermometer showed a reading of 13.4 on the handheld multimeter, which corresponds to around 330 degrees; the DCS displayed 360 degrees. When a signal was sent using a signal generator, the DCS showed a value 30 degrees higher than that measured on-site. After disconnecting and reconnecting the wires, normal operation was restored. The temperature had been consistently high and fluctuating – could this be due to a short circuit in the wiring or some other issue? The card holder hasn’t been moved at all
Is it a poor connection, or is it an issue with the wiring?
I also want to figure out exactly what the problem is. It seems to be related to the wiring, but wiring issues shouldn’t cause a temperature increase of 30 degrees
At first, when I used a multimeter to check, the circuit was disconnected; even after reconnecting the wires, there were still fluctuations. In the end, it only worked after pulling the wires out of the meter’s casing and reconnecting them properly
It would be better to use a temperature transmitter, which can output a 4-20mA signal
Is it because cold-end compensation was performed on the DCS side? The voltage value measured on-site has a cold junction at the ambient temperature, resulting in instability. On the DCS side of the cabinet room, the cold end of the temperature sensor has its value compensated to match the temperature in the cabinet room, resulting in a relatively constant value; the actual temperature at the site is then determined through calculations performed by the DCS.