Signal conditioning for NDIR sensor

[columbine84]

I am wondering why they use a thermistor to monitor temperature when they have a reference detector?

https://www.st.com/resource/en/application_note/an5571-signal-conditioning-for-ndir-sensor-stmicroelectronics.pdf

 

 

[Peter BENSCH]

Welcome @columbine84, to the community!

this reason is actually also stated in the AN5571 you referenced:

[page 2] The reference junction is at the reference temperature and, in order to ensure a good stability, this reference junction is generally measured by a thermistor.
...
[page 3] The output of the thermopile can vary depending on the ambient temperature. A thermistor is generally used to compensate this possible drift.

Hope that answers your question?

Regards
/Peter