Dual Loop PID, a accurate bed surface temperature

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+1 on including a dual thermistor input control feature.

I have a Klipper powered Jubilee with a thick MIC6 bed, located in an insulated enclosure with a temperature controlled fan. While my setup delivers great thermal reproducibility, I would still like the bed temperature to be driven by a thermistor that is closest to the surface of the bed while not needing to worry about the silicone heater over-heating as a result of an overshoot.

Contrary to some of the opinions in this thread and on the Github issue, I do not see this as unwarranted complexity and here’s why.

  1. For a user, it’s more complex to set up startup macros and offests for different materials (target bed temperatures). It is far preferable to just add two lines of config to introduce another thermistor input and run some calibration routine to tamper overshoot.

  2. I do not agree with the discounting of “quality of life” improvements such as heat up times. 3D printing in general is at a point where things like ease of use and print speed matter. Shaving off 30% of the time it will take for temperatures to stabilize (as suggested by a simulation posted here) is a good prospect to go after.

In-short I like this idea a lot, especially nowadays where MIC6 plates tend to come with pre-drilled holes for plate thermistors.

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