How to handle discrepancies between the DCS control display system and the on-site instrument displays
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In production, it is common for the data displayed in the control room to differ from the actual conditions on site, especially when there are no actual on-site data for comparison. How should such situations be handled?
Are the measurement points in the same location? If they are not in the same location, of course the display might differ. Is it a sensor that outputs two signals? Could it be a wiring issue? Is it one local instrument and one remote instrument? The source signals for the two instruments may be different, or they might not be the same. Are the two instruments integrated? Even integrated versions can vary; for example, bimetallic elements with remote transmission have two different measurement principles, and the measurement results can also differ in such cases.
““The operation display data in the control room does not match the actual conditions on site.” It is likely referring to the transmitter; the replacement method is a good approach – replace the transmitter, the cables, or the module, and send standard signals, which can be done directly at the site by feeding them to the module.
There is another scenario where the instrument itself has display and output functions; in such cases, discrepancies can also occur between what the instrument shows and what is displayed on the computer. This seems to be related to the load capacity of the meter; there is a difference in the current output by the meter when it is measured without a load and when it has a load connected. However, they are all basically within the allowable accuracy range.
Thank you to all the experts; your advice is correct. Since this isn’t my major, I now need knowledge in this area to work better.
If what the original poster is saying is that the signal is accurate sometimes and not accurate other times, I think there must be interference occurring from time to time; it’s possible to check whether there are any sources of interference along the signal line path and around the attenuator, such as electromagnetic interference or vibration-induced interference
Another possibility is the case of thermal and pressure compensation. The value obtained after compensation calculation (the value displayed in the control room) is generally different from the value of the field transmitter without compensation.
Check whether the signal is normal; if it is, try installing a signal isolator!
To determine whether it is a loop, it is first necessary to understand the structure of the loop and examine various intermediate components within it