We've had some problems recently with a common commercially available temperature controller, which we've tracked down to inadequate EMI filtering in the temperature controller AFE and use of unscreened cabling in the wiring harness provided by a different vendor (the 10k NTC has a 100uA sense current so is a high-impedance node which is very prone to pickup even at 50Hz).

To solve this, I'd like to swap out these temperature control units for Thermostat, but there are two annoyances:

1. The specified temp co of the Thorlabs chip is quite high and likely to be problematic if we don't temperature stabilise Thermostat, which is a pain
2. We use a resistive heater rather than a TEC for this project. AFAICT there is no software option to make the Thorlabs chips run unipolar (AFAICT the designers didn't consider resistive heaters as an option so didn't bother to implement this in firmware). So, if any transient reduces the heater current below 0 then it will go into thermal run away.

So, I'd like to revive the discussion about replacing the Thorlabs chip with something along the lines of @cjbe's design based on a 24-bit ADC and the Maxim TEC driver IC. As a reminder, the big win from using a 24-bit sigma-delta ADC is that the sample rate is high and the ADC includes very good digital filtering (including extreme rejection of 50/60Hz signals). Combined with a basic CM/DM analog RFI filter, this provides a level of EMI rejection that is essentially impossible to achieve in the analog designs that seem to be used in almost all COTS units. Using @cjbe's prototypes of this design, we were able to achieve stabilities better than 100uK long term without issue.

As I see it, the main challenge here is software. The hardware redesign is very easy and I'd be happy to do that myself using @gkasprow's Altium library. The more involved part is writing decent software: command handler; simple PI(D?) loop; some basic features like thermal runaway detection, current limiting, anti-wind up, etc. I don't have time to do that part. @gkasprow do you have a student who might be interested in doing that? (otherwise, if anyone is potentially interested in funding M-Labs to do this then let us know!)