Hi - I'm designing a PLC verification stand, and need to simulate the devices that will be attached to it. Three devices output 4-20mA and the PLC provides +24VDC power on a two-wire interface. One device is a thermistor that varies from 200 ohm at 105 degC to 5000 ohm at 10 degC.
I need to simulate a consistent profile output, which would require software.
For the 4-20mA outputs, I was looking at using an NI-9265 (https://www.ni.com/pdf/manuals/374067a_02.pdf) -- however, I'm not sure it can output current on a two-wire setup that has a 24VDC power supply as loop power. The 24VDC is integral to the PLC (as it is expecting a 2-wire transducer that needs to be powered).
I'm not sure how best to simulate a thermistor. I literally need a variable resistance that I can control via software. I was thinking of using a potentiometer with a motor... although, that sounds crude and am open for input.
Thank you.
