How to measure the voltage across a large resistance(Mega Ohms) with SCXI 1302

[StCharles]

As I'm measuring a voltage across a relatively large resistance (over a mega ohms) with SCXI 1302, I'm wondering whether the voltage measured was still accurate enough? If not, how do I improve the measurement?

[GarPar]

Hi StCharles-

     The 1302 is a terminal block for an SCXI module.  It doesn't actually take the measurements; rather, it routes signals to the companion SCXI module.

     That being said, your measurement accuracy depends on the type of measurement you are taking.  Are you taking a single voltage measurement across this resistance?  Meaning, are you only reading this channel or are you measuring this channel along with some other channels at the same time?  If you are taking a single voltage measurement across this device, and you are taking a differential measurement, then your voltage reading will be as accurate as your SCXI module will allow.  If you are multiplexing through several channels, and this voltage measurement is one of them, then you may not be getting an accurate measurement because the high input impedance would not allow your SCXI module to settle to the appropriate voltage level.  This could cause ghosting in your reading.  If you are experiencing ghosting, you can refer to this KnowledgeBase article to troubleshoot.

     I hope this helps.  Best of luck with your application!