Issue regarding inconsistent 4-20ma outputs from the two channels of the signal isolator
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The Jiubo flow meter provides a 4-20ma input signal, which is divided into two paths: one goes to the data acquisition unit and the other to the DCS. The 4-20ma outputs from the isolators on these two paths are not identical. What could be the reason for this? The same issue persists even after replacing it with a new 24V power isolator. Is 24V also supplied from the DCS side? Please analyze it
First, ensure that the wiring is correct; then check the degree of error to see if it falls within the allowable range. If it exceeds the tolerance, calibrate it using standard instruments. For those that cannot be calibrated (such as isolators), replace them.
One is 9.2 ma, the other is 9 ma
Can isolators also be calibrated? It should be the cheapest one; I’m going to the site today
First, test the actual output current value of the flow meter; if there is an error on the DCS side and this error remains constant, it can be corrected within the configuration
An error of 0.2mA isn’t that large; if it’s a DCS active system, the error will be even greater. It is recommended to check whether the DCS configuration cards are in active or passive mode, and then calibrate the isolator
There are some isolators that can be adjusted; you can use a screwdriver to turn a screw or use a manual controller for adjustment. I think 0.1 is acceptable, but 0.2 is indeed too much of a difference.
The output terminal of the directly measured signal isolator should have nothing to do with the DCS