USB-6008 -1.4 offset

[DAQNewby]

I know this question has been answered before, but I still haven't figured this out.  Here's my problem:

I am reading a voltage output from a picoammeter, where the voltage out is proportional to the current being measured.  I have the connection to pin 5&6 (differential mode) and designate differential when I create the task.  Despite this, I am reading an ~-1.4V offset in my signal.  I have read the "kb" that has been posted, but I have designated both in DAQmx and in my VI that this is a differential connection.

The most frustrating thing is it was working this afternoon, and after I closed LabVIEW and came back, it no longer worked.  The funny thing is if I leave it connected in differential (pin 5&6, I triple checked) and designate RSE connection, it doesn't give me the offset.  Can someone please help?

[G_Lo]

DAQNewby,

Could you try measuring differentially on another channel to further troubleshoot the issue?  Also, I would suggest looking at table 1 of the Field Wiring Guide which shows different connections for all configurations.  If your source is floating, it is recommended that you utilize resistors in your application.  Also, I am not sure which kb you are are referring to but I have included a couple of documents that may provide some further insight into the issue as well.  Also, you said that it did not work after you closed LabVIEW.  When you reopened your program, did anything get reset to its default value?  You can save the configuration on your front panel by selecting Edit>>Make Current Values Default.  Hope this helps!

6008 Incorrect Readings

-1.4V Offset with RSE Connections

[DAQNewby]

Yea, when I use my ai1 to measure a known voltage from a voltage supply it is incorrect, yet when I use ai2 it is correct.  I think one of my channels was destroyed when I had an electrostatic discharge in my experiment.  Now to keep that from happening again...

Thanks for the help,
Steve