Measure device current at the DCS end
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As the title indicates, it measures the current of fans or mixers; a 30/5 current transformer is used, and the signal is converted to 4-20MA via a transmitter, with a range of 30A. The data read by the two sets of instruments do not match each other; after replacing one current transformer, the data still does not correspond to those of the other two. I would appreciate some advice on how to perform the calculations or make the necessary settings
The DCS configuration ranges are consistent. The transmitter is the same. Unless the current is different
On the same cable, the range must be the same. The basic operations should work fine; if the transmitter doesn’t move, the results will be different!
Transformers also have range specifications, such as 0-50A, corresponding to 4-20mA or 0-5V. Any of these options are acceptable; as long as they match the range settings on the DCS side, there should be no discrepancies
Starting with the measuring element, for CTs, it’s 30/5, which means the maximum current range is 30A, and the transformer outputs 5A corresponding to that. At zero current, the output should be 0A. This depends on whether your current transmitter accepts an input range of 0-5A, with a corresponding range of 0-30A and an output of 4-20mA. Additionally, it’s important to check whether the DCS’s range is also 0-30A; it’s all about these corresponding relationships
It is recommended that you measure whether the output current of 4-20mA matches what the ammeter shows. Under normal circumstances, as long as the range is appropriate and there are no issues with the DCS input signal, such a problem should not occur; therefore, it is advisable to conduct a measurement in order to determine the cause
It seems that the transmitter’s 4-20mA output doesn’t correspond to its 0-5A input. Let’s list out the specific data; perhaps then we can see where the difference in the measurement range lies.