Floating positive voltage in my scxi-1166/1366

[cfreeman]

I have a scxi-1001 chassis housing a 1166/1366 module and connector block.  I have a +24vdc power supply wire wired to the common terminal in ch0 and a wire out of the Nomally open (NO) terminal to external source.  When using the SWITCH application in MAX I can close the relay on ch0 and confirm the 24vdc.  When I open the relay, it retains a voltage around 1.3vdc (as measured from the NO output wire and teh negative side of my power supply) 

Is there a reason for this? It seems like for some reason the NO circuit is retaining some voltage. 

I appreciate the help!

[G_Lo]

Hi cfreeman,

I believe I have a possible explanation as to why this could be happening.  When measuring Normally Open (with the relay not switched) there should be no current through this connection.  I believe the issue is that you are measuring Normally Open with respect to the negative end of the power supply.  Your power supply may output 24 volts but the negative could have a potential that is different than zero.  Unless you are measuring normally open with respect to ground, you may receive some kind of offset in your measurement.  To verify that your relay is open, meaure the resistance from NO to COM and see that it is infinite (no connection between NO and COM is made).