Does the pseudodifferential input of PXI-6115 prevent use of SCB-68 CJC to monitor temperature?

[Raj_Gandhi]

I'd like to utilize the CJC of an SCB-68 to monitor ambient temperature.  I can get it to work with one DAQ but not the other.  My evaluation setup uses DAQ Assistant and two SCB-68 with switch config: s1 left, s2 left, s3 down, s4 up, s5 up. Scale and read AI0 voltage.

PXI-6052E

 - Gives the correct result (about 25C and moves when I touch the sensor) with either SCB-68.

PXI-6115

 - Output basically floats (about 75C).  Grounding the left node of RC13 on the SCB-68 makes the output go to about 0C.  Schematic is on page D-2 of "SCB-68 Shielded Connector Block User Manual."

I've tried toggling S4 between Differential and RSE; the 6052 behaves as expected but there's no affect with the 6115.  DAQ Assistant grays out everything except pseudodifferential for the 6115.

The 6052E has fully differential inputs but the 6115 has pseudodifferential.  Is that why I can't use the SCB-68 CJC on the PXI-6115?

[Ali M]

Hello Raj,

Please refer to the following recommendations: set up AI0 as a voltage task and another channel eg. AI1 to acquire temperature. Attached are links with more information on how to set up CJC using the SCB-68/pseudodifferential and differential inputs.

1. http://digital.ni.com/public.nsf/allkb/16F71843CC7892D4C1256BE3004E1043?OpenDocument

2. http://zone.ni.com/devzone/cda/tut/p/id/6962#toc2

Regards,

Ali M

Applications Engineeer

National Instruments