Thermocouple temperature offset

[stellator]

Hi, is it possible to correct for a temperature offset between the hotend sensor reading and the actual temperature within the nozzle via gcode? In this case I would need to give it a slope of 2.75 minus 54°C (y=x*2.75-54) to correct a reading of 100°C for an actual temperature of 218,5°C (yes that is huge but it cannot be helped hardware wise currently).
thx!

[dc42]

The firmware doesn't currently provide a way to adjust the reading from a thermocouple, only to select between different types of thermocouple.

[stellator]

Thanks for the quick reply! Than its on my wishlist I guess it would make sense for everybody who would like to set a realistic temperature? Maybe one could just put the formula somewhere in the Duet web control interface - I never did program html but maybe its possible to do calculation within the code similar to python?

[r123]

@stellator Methinks this could be useful for heated beds too. I just fitted a magnetic layer and a spring-steel sheet (PEI coated by Subtle Design) and a good approximation is to raise the temperature by 5C (the corners end up cooler in this arrangement). Instead of "learning" new temperatures for old materials would rather just add the 5C in as an offset and keep the Bed temperatures in the slicer as they are.

So it's a feature suggestion.

[Phaedrux]

Moved to firmware wishlist.

[atmark]

I'm currently building a big pellet extruder with three different temperature zones. Since, obviously there is quite a big spread in the sensor quality and the way they are attached to the band heater, I would also warmly (no pun intended) welcome individual temp offsets for the sensors.

[jens55]

Yes, I too would like offsets to be available

[Tinchus]

@jens55 @Phaedrux @dc42 Sorry to bring this alive. Is there a chance to get this offset now in 3.3 version?

Lets say my sensor shows me 200 degrees, but I know as a fact that the temperature is actually 180 degrees. Can I configure the thermistor in the formware so I assign an offset of +20 or -20 degrees?

Thanks in advance

[dc42]

@tinchus are you talking about a thermistor or a thermocouple?

If you want RRF to lie about the temperature read by a thermistor, you can do that by giving RRF different T, B and (if necessary) C values in the M308 command. Adjust the T value to get the reading you want at 25C, and adjust the B value to get the reading you want at high temperatures.

[Tinchus]

@dc42 Not lie. I want to be able to adjust the offset Im observing in the thermistor readind between the place the thermistor is located and the real temperature in the hotend. My example saud 20 degrees, that was exagerated. The correction I want to do is exactly 7 degrees