Are PLC analog input modules active or passive?
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Some of the meters on site send signals of 4 to 20 milliamps to the PLC; the components that receive these signals are definitely analog input modules. I want to ask who provides the 24 volts – since it’s a two-wire system, I don’t see any 24-volt supply in the analog input modules.
If it is a two-wire instrument, check to see if there are no safety barriers or signal distributors in the control room; if such devices are present, then it is they that supply the power
The 24V power supply for the field transmitter should be powered directly by a 24V DC power source, with the power supply connected in series within the 4–20mA circuit.
If you are a Siemens 7KF02 module, then you need to adjust the small jumper squares on the side.
Generally, they are powered by a dedicated 24V power supply.