04-10-2019 08:15 AM
I am trying to configure my PXI-2722 Resistor Module to act like a 3-Wire RTD Sensor.
I am using Channel 0, with these Relay Positions: b0shunt = Closed, b0 = Open, bc01 = Closed, b1shunt = Open, and b1 = Closed. See attachment.
My LabVIEW program can change the resistance across Pins 2 and 20 which is what I expect.
My problem is I have an Open Circuit (infinite resistance) between Pins 2 and 1. So my solution will not act like a 3-Wire RTD. What am I doing wrong and how can I act like a 3-Wire RTD using PXI-2722?
Solved! Go to Solution.
04-10-2019 09:13 AM
Have a look at the spec... pretty high uncertainties (1% to 10%! depending on range) and 0.25Ohm resolution.
Assuming a Pt(100 or 1000 or ..) : 1K change is less than a 0.4% resistor value change.
Well it migth work with NTCs ... and individual calibration .. depending on the accuracy needed..
3 wire is not needed 😄
04-10-2019 01:30 PM
Henrik Volkers, Thanks for taking the time to reply, but I don't understand what your point is?
I am wondering why when I Close Relay b0shunt, that Pin 20 and Pin 1 are not shorted (low resistance). I measure an Open (high resistance) between pin 20 and pin 1.
04-10-2019 03:39 PM
Sorry, I mixed up a source with a RTD measurement device 🙂
04-18-2019 06:33 AM
I have my 3-Wire RTD Simulator working. I setup the relays to connect to the external connector pins that I require, before calling ni272x Write Resistance. I removed all references in ni272x Address Bank Relay so they only change the Resistor Relays and never change the shunt or bypass Relays. I changed my Requested Resistance and used Front Panel to monitor Relay Positions and measure the Resistance at the External Connector.