Internal thermocouple readings for CJC appear to be way off - I have it at room temperature and it is reading 437K.
This is without any additional thermocouples plugged into any of the AINs
When I do plug in thermocouples readings are in 439F (again this is at room temperature)
This has been working for the last year - recently moved the device to a different position on the oven and now wild readings
Is there a way to recalibrate the internal thermocouple? I am getting consistent readings on all my thermocouples they are all just very wrong.
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That sounds like the internal temperature sensor may have failed. The AIN system may be malfunctioning as well. Let's do a couple checks to see if the unit is operating correctly.
1) What do you get form the TEMPERATURE_AIR_K register?
2) Set AIN0 to single-ended, connect a jumper from AIN0 to GND, What does AIN0 read now?
AIN0 = .000015 with the juper connected (much higher without it connected)
TEMPERATURE_AIR_K = 494
The looks like the temperature sensor has failed. We either need to RMA the unit for repair or switch to an external CJC sensor.
If you would like to RMA the unit please follow the instructions under the repair section here: https://labjack.com/about/returns
Thanks for the fast repsonse - how do I switch to an external CJC sensor? what all is required? I think this is a good starting point before doing the RMA if it would be faster fix
not sure if it is required but I do have a spare CB37 Terminal Board that I bought at one point thinking I was going to be using a whole lot more thermal couples than I actually do
Config_B allows you to specify a modbus address to read from to get the CJC, Config_D and Config_E provide slope and offset calibration constants. Valid registers are analog inputs. The sensor needs to be pretty linear something like a LM34.
Relevant doc page:
https://labjack.com/support/datasheets/t-series/ain/extended-features/thermocouple
Our thermocouple appnote is also helpful:
https://labjack.com/support/app-notes/thermocouples/t7