I ran into some issues; I’d appreciate everyone’s advice.
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There is a temperature controller whose input signal is a 4-20mA signal from a transmitter, with a range of 0-1.6. A few days ago, for some reason, the PV of the thermostat was much higher. ①The measured signal was 8 mA, which matches the value shown by the local instrument of 0.4; however, the PV reading on the temperature controller was around 1.5. ②I tried to apply a 10mA signal manually as well, and the PV value went up to around 1.9, which is well above the range. What is the reason? How should this be solved?
I’m sorry, I don’t quite understand what a thermostat is, but since you mentioned it’s a 4-20mA signal, it’s probably similar in nature. If it is a transmitter, such a fault occurs when the range settings on both sides are different. For the instrument side and DCS side, I hope this can help you. Thank you
It’s possible to check the range of the controller; if it was working fine before and no one has adjusted this parameter, then it might be a problem with the controller. Looking forward to the results
10mA corresponds to 1.9, with the full scale reaching around 5.1. If it is caused by human error, the upper limit can be adjusted; if it is not due to human error, there is a problem with the gauge or the set parameters have not been saved, in which case resetting it will resolve the issue
It might be that the parameters weren’t saved; just reset them
Thank you. I have checked; the ranges of the transmitters, temperature controllers, etc., are all set correctly.
The range check has been performed and the settings are correct. If that doesn’t work, try a new controller
Thank you. I checked repeatedly, and the upper and lower limits of the range have indeed been set correctly. A few days ago, during the maintenance of the electric valve controlled by the thermostat, someone changed the parameters incorrectly.
Based on the information provided, I personally think that the gain in the thermostat has been altered; by inputting a standard signal, the gain value can be adjusted again.
Please share your opinions and help solve this problem.
It’s possible that the display coefficient (display value/actual value) has been increased