Connection issues between the flow meter and the frequency converter
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There is an electromagnetic flow meter at the pump outlet; the pump’s speed needs to be adjusted according to changes in flow rate. The flow signal must pass through an inverter in order to regulate the pump’s speed. Additionally, the flow rate should also be displayed on the PLC. I would like to ask whether the 4–20mA signal from the flow meter first needs to be sent to the PLC as an AI signal, and only then does the PLC send an AO signal to the inverter?
This post was last edited by ssln123 on 2011-6-30 at 13:28. To display the flow rate on the PLC, the PLC requires an AI module. However, some modern frequency converters already have PID control built in, so it is possible to connect the flow meter’s signal directly to the frequency converter without needing an AO signal from the PLC. The flow meter simply needs a two-way safety barrier, one output leading to the PLC and the other to the frequency converter.