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analog input 4-20mA


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I am using an V350-35-T2 with IO-AI4-AO2.  I use an analog out 4-20mA to control a valve.  I use an analog in 4-20mA to read the flow.

The current from the flowmeter is 4mA when no flow.  I measure 4mA with multimeter at the input port of the IO.  However, the parameter in the software is reading as if the signal is too low.  To test, I connected the analog output signal to the analog input port, and then set the current to 4mA.  The software then reads the signal correctly.


I find this very strange, and I wonder what can be wrong.  Is it possible that the voltage from the flowmeter is too high?  It is around 21V.  By comparison, the voltage from the analog out signal is around 2V.


I would be very grateful for any suggestions to try.

all the best




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