Progressively removing the case. The cold-junction compensation board is not yet visible. It sits below the main board and behind the black plastic plate with slots for thermocouple connector blades.
Interestingly, the CJC board is made with metal (copper) substrate. It promotes heat transfer and reduces temperature gradient between the cold junctions and the sensor which measures their temperature. (The CJC temperature sensors are better visible on another photo below.)
Thermocouple connector added to show where the contact between thermocouple materials and copper pads on the cold-junction compensation board takes place.
Cold-junction compensation sits on its own daughter board, and it's somewhat insulated from temperature gradients that may be generated by the main board.
- SOT-23-3 ICs between each pair of the thermocouple pads are the sensors which measure the cold-junction temperature.
- An EEPROM (AT25010 ) suggests that the CJC board is calibrated separately from the main board and the coefficients are stored in this EEPROM.
- LT1034 is a dual voltage reference
RelatedMaxim App Note 4026 Implementing Cold-Junction Compensation in Thermocouple Applications
Discussion about cold-junction compensation in this Analog Dialogue article (2010).