PXI-2503

[Clint1000]

Don't know if this is the correct forum..

I have a PXI-2503 connected to a PXI4065...see attachment. The 2503 is connected as 2 wire 24 x1 topology.

On one of the channels (#5) I have the wiper of a pot connected. The max of the pot is 500 ohms.Other channels on the mux connect to voltages (<10 vdc).  My question is the way I have it set up .."OK"???  Can I have voltages on some channels and resistance measuments on others??  I open and close them as needed.   I ask because every so often I measure 700 ohms on ch 5 which is impossible.  Wiring is correct.  Could one of my channels be sticking maybe adding another path??  I'm at a loss to explain where I'm getting 700 ohms on a 500 ohm resistor.  Do I need to put settling time in my code?

BTY: I use AB0 as needed for 4 wire resistance measurements.

Thanks.

[PezDeSpencer]

Hey,

I do not see anything blatantly wrong with the wiring, taking a glance at your schematic. Are you doing "hot" switching or "cold" switching, where the voltage is either on or off on the channels as you are switching?

Do you have any settling time in your code? How fast are you switching? It is possible the aperture time is not long enough based on your switch speed. 

Are you allowing for 30 minutes of warm up time in the beginning for the 4065?

Spencer R | NI

[Clint1000]

I'm doing hot switching..Its a UUT so the power is always applied to the MUX on the open channels.  I close them as needed to test.

The testset (w the 4065) is on constantly so the DMM should have ample warmup time

Settling time,aperature and switching are the defaults that come w NI Switch.vis.  I haven't chg'd them.  Will try those.

Thanks..

[PezDeSpencer]

Please try that, and you can post the results back on this forum. 

Another clarification question, is the line only reading 700 Ohms every once in a while, or every time? Is there any pattern to when it reads 700 Ohms? Is it functioning as expected otherwise?

Is there anything else wired to that line besides the potentiometer that could add extra resistance? Such as on another switch line that's not fully disconnected. 

Spencer R | NI