In the Siemens S7-300 hot water station, why are the values of the analog inputs on the high side?
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In the Siemens S7-300 hot water station, the values of the analog inputs are consistently too high. This issue disappears after some time; the wiring is in good condition and the terminals are not loose. I’m not sure what could be causing this problem
Check whether the power supply is stable and the grounding is proper.
What is the input value? Level or temperature? 4-20mA or something else? What is the basis for saying it’s on the high side? When the value was on the high side, was it checked whether the circuit signal was normal, for example, whether the 4-20mA value was within the normal range? Was the signal circuit connected directly or through a safety barrier?
There is both level and temperature, in 4-20mA format. The high value suddenly increased; when it was at a high level, the circuit signal was normal. Is there a direct connection to the card holder in the signal circuit?
There must be some interference. Check whether there are any abnormalities in the voltage of each channel with respect to ground. Not only this module needs to be checked; if no abnormalities are found in this module, then check the channels of other modules as well. Abnormal voltages from other modules could also cause interference. If the source of interference cannot be found for the time being, you can try installing isolation barriers on the channels first.
I guess it’s also interference; it will get better after some time. But there are no sources of interference in the vicinity, and the frequency converter is far away as well
Analyzing it based on common sense may not correspond to the actual situation, so rule that out first. Or you can look through the fence; if it disappears, it means it’s still due to interference.