Virtual Ground on NI 9217

[estbiostudent]

I'm using an NI 9217 connected to a DAQ to take 4 wire measurements of resistance across a custom built platinum RTD. The RTD is exposed to a salty water solution a few micrometers away from a platinum wire that is also exposed to the salty water. The potentials on the platinum wire as they go through the water near the RTD are +6V to +5.75V from earth. I would like to verify that I can set "com" on the NI 9217 to +5V from earth to prevent current flow through the water. The spec sheet seems to indicate this works, but before I go and mess up the module I wanted to verify.

[even-And]

Hey estbiostudent,

Could you point me to the spec sheet that shows that this works

[estbiostudent]

NI 9217 - Data Sheet - National Instruments: http://www.ni.com/datasheet/pdf/en/ds-193

Page 6, section "Safety" 

Safety
If you need to clean the module, wipe it with a dry towel.
Maximum Voltage 
Connect only voltages that are within the following limits.
All terminals-to-COM ±30 V

[estbiostudent]

and then also "Available channel-to-earth ground double-isolation barrier for safety, noise immunity, and high common-mode voltage range" under "key features" found on page 2

[even-And]

Yes, you are correct you will be able to set the "COM" to be +5V above earth!