Signal Conditioning

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Why do I have an offset when monitoring a thermocouple, using the SCB-68 and its built-in CJC?

I am using a SCB-68 connected to a DAQCard AI-16E-4. I have configured Ch 0 on the SCB-68 to be the CJC sensor, and I've connected a thermocouple to Ch 1, using differential mode.

When I use MAX and 'test' the thermocouple channel, the reading I get is approximately 10 deg.C lower than the correct value (although the sensor responds in the correct manner, the value is always offset by 10 deg.).

Is there another step I'm missing in setting up the thermocouple channel (I've set the CJC setting to "Built-in") on the Properties dialog in MAX)?

I've tried a T-type and a J-type thermocouple, with similar results.

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First thing I'd recommend is verifying the switches on the SCB-68 are set correctly using the SCB-68 Installation Guide.

Also, in order to determine whether the virtual channel is scaling properly or not, run the Test Panels for the DAQ board and read the raw voltage being read from your channel. Also read CH 0 and confirm whether the CJC sensor is returning reasonable results.

The offset may also be due to a calibration issue. You can short your differential channel and test the reading. It should be reading very close to zero. If it is far off of zero, it's time for calibration.

There is some more details and troubleshooting advice at:
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