Cold Junction Compensation for Modules Without Built-In CJC in FlexLogger

Issue Details

I am trying to setup thermocouple channels in FlexLogger and set their Cold Junction Compensation (CJC) source, but for some cases, like using a PXI-6289 with a SCB-68A, I can only choose the Constant option. I need to be able to select a channel as the source of the CJC.

Solution

The option to select a channel as a Cold Junction Compensation (CJC) source was added to FlexLogger 2023 Q2, to be able to select this it is recommended to upgrade to that or a newer FlexLogger version.

For modules without a built in CJC, such as the PXI-6289, you need to use an accessory with a temperature reference, like the SCB-68/SCB-68A, and configure it to enable the temperature sensor in the AI0 channel, as explained in this article: Using Cold Junction Compensation (CJC) on the SCB-68 or SCB-68A. You can then configure the temperature enabled channel AI0 in FlexLogger with a Constant CJC source, that will provide the CJC for the rest of the channels:



For the rest of the thermocouple channels you can set the CJC source to Sensor and map the CJC sensor setting to that channel created to provide the CJC:



Once configured it will look like this, taking as an example a PXI-6289 with AI1 referencing AI0 as its CJC source:



For older versions of FlexLogger, you would need to work around this by using calculated channels to:

1. Convert the CJC channel to temperature.
2. Subtract the CJC temperature from a thermocouple channel.

Additional Information

If you have modules with a built-in CJC sensor, like the PXIe-4353, simply set the CJC Source to Built-in when configuring the channel in FlexLogger.

For more new features introduced in different FlexLogger versions you can refer to: FlexLogger New Features and Changes