The display value of the pressure transmitter does not match that of the DCS – what is the reason?
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The reading displayed by the field pressure transmitter does not match the value shown on the DCS; the configuration is correct, and both the pressure transmitter and the DCS have the same range of 0~2.5 MPa. Previously, the readings from the field pressure transmitter and those on the DCS were consistent, but this issue only started appearing recently. I would appreciate it if experts could help analyze this situation.
The local and remote readings don’t match; I’ve encountered this issue several times as well – it’s going back to the factory
How much is the difference? The display gauge of the field transmitter is inaccurate; check the DCS cards, as well as the cables in between, one by one.
It’s easy to confirm: use a multimeter to measure the output current of the transmitter, and then calculate what pressure value it should display. If the displayed value is incorrect, that’s where the problem lies.
Measure the current. Check that it matches the header, just like with DCS. It is then possible to roughly determine whether it is a system issue or a display issue. It is also necessary to confirm with on-site pressure gauges whether the transmitter is displaying correctly.
I’ve encountered this situation a few times as well; in most cases, it was a problem with the field transmitter. As long as the DCS current signal is correct, it is the responsibility of the field transmitter. Of course, it could also be a problem with the safety barrier. It can be checked in sections.
The range and the card are fine; it must be a problem with the transmitter
If the settings are correct, check the supply voltage to the transmitter, compare the output current at the transmitter side with the current after it reaches the indoor area, and verify that there are no broken or grounded cables.
How much is shown for each? Is it beyond the upper or lower range limit? Remove one of the signal wires from the transmitter, connect a multimeter in series to measure the current, and see which reading matches that of the DCS and the gauge
I have another question: For a 3051 differential pressure gauge with a 2-wire connection, the voltage measured when the wires are connected is around 5V, and the display shows full-scale values; however, when the terminals are disconnected, the voltage returns to 24V. Is it possible to determine any fault codes for the transmitter? How should this be solved?
First, use a multimeter to measure the current value output by the gauge; convert it as necessary. If the reading shown by the gauge is correct, then check whether there is a value being sent to the analog module. It could be a problem with one of the channels in the analog module, so try using a different channel and examine the program as well. The problem we encountered a few days ago was caused by a damaged module channel in the PLC; replacing it resolved the issue~