No logged value on AI 7 when logging 8 thermocouples

[RayOermann]

Attempting to log 8 thermocouple outputs after signal conditioning (gain x100) with 0V referenced outputs through an SCB-68 into a DAQCard6062E.  Using a Labview VI configured to log 0-500mV, RSE mode.  Logging from 1 to 7 thermocouples works fine, when the 8th thermocouple is added it always reads 0.000.  Tried swapping all thermocouples around - no difference, AI 7 always reads 0.000.  Tried using AI 8 (and others) but still reads 0.000.  Fed in a reference voltage (0.42V) into AI 7 and placed Thermocouple 8 into AI 8 and this recorded the reference voltage correctly, but AI 8 now read 0.000.  Tried swapping all inputs to use AI 8 to AI 15 and found AI 8 to AI 14 worked fine (like AI 0 to AI 6 before) but AI 15 read 0.000.  VI being used is attached

[Wayne.C]

Do all the signals appear correctly in the waveform display? 

[Ben]

Thermo couples as RSE strikes me a strange. I would expect it to be differential where AI0 is paired with AI7 etc.

Sorry I can't say more.

Ben

[RayOermann]

Channel AI 7 is displayed as zero in the waveform display during acquisition

[RayOermann]

I'll try NRSE mode with all the GND's connected to AI Sense.  Thanks

[NIquist]

What are you using for "signal conditioning"?  It sounds like its channel 8 may be the weak link.

[RayOermann]

That was my original thought, but rearranging all the channels, different thermocouples into different amplifiers and different amplifier outputs (signal conditioning circuits) into different Analog Inputs (0-7) didn't change the fact that AI 7 (the 8th logged channel) was zero.  I'm using a custom made 8 channel amplifier (100x gain) to amplify the outputs of FW05 fine wire E-type thermocouples.  The two stage amplifiers use LTC1052CN8 op amps.