Siemens positioner issues
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Dear all, today at our factory we were dealing with a problem related to the feedback from Siemens positioners. The signals sent from the DCS did not reach the positioners, and only 2.5 MA was transmitted from the DCS to the local positioners; as a result, the valves remained in the open position. What is the cause of this issue?
It is recommended to measure the current directly without using a locator. If it remains the same, measure the current directly from the AO channel. Such issues need to be ruled out for this loop measurement.
It might be that the channel is damaged; try using another channel
Determine whether it is a problem with the AO card channel, the cable, or the locator, and investigate step by step.
Since it’s an AO signal, it should have little to do with the positioner; even when the positioner is disconnected, the measurement will still be 2.5mA
At the site, a signal is sent to the locator using a signal generator to check whether it operates properly; if it does not function correctly, then it is a problem with the locator. If it works fine, then it is necessary to verify whether the current output of the safety gate matches the channel output; if they do not match, then it is a problem with the safety gate. If they do match, then it is necessary to check whether the channel is functioning properly.
Measure the current and voltage directly on the DCS card; first, you need to rule out the possibility that there is a problem with the DCS itself； Next, check the wires to see if there’s a problem with them! ! Finally, judge the locator ； A signal generator can be used to send a signal directly to the locator to see what’s going on This will help you analyze what the problem is.
The value of 2.5mA at the field locator indicates that it is not a problem with the locator itself. It is recommended to measure the output current after the card; if this value is normal, then check whether there is any ground short-circuit issue in the wiring