Onyx heated bed Rev 7 temperature reading

[WZ9V]

I have an Onyx Rev 7 hooked up to a 12V supply through a DC-DC SSR driven by a SmoothieBoard 5XC.

I have the thermistor setup as a Semitec in the config but my readings seem to be off in comparison to an IR thermometer.

When the IR reads 21C in the room the bed is reading 19C or so. At 60C in Pronterface the IR is reading 65C and at 101C in Pronterface the IR was reading 122C. Is the Semitec the right one to use?

[bot]

On my duet 0.8.5, with a 104GT-2, I use a beta value of 4650. This makes the thermistor read the same as the surface of my PEI bed with an IR thermometer. Between the onyx and the 1/8" PEI I have an .050" aluminum spreader, a mirror that is approx 4-5mm, and two layers of kapton tape. See if you can set the beta value yourself. the resistance at 25 degrees is 100k ohms

[derzaubererer]

my ir thermometer reads 10° more than the thermistor
where do you have your calculations from?

[WZ9V]

Is that for me or bot?

Would I be better off taping a thermocouple from my DMM to the bed instead or using something else instead of the IR thermometer?

[derzaubererer]

Is that for me or bot?

Would I be better off taping a thermocouple from my DMM to the bed instead or using something else instead of the IR thermometer?

its for both
my ir thermometer is 1 degree precise but ir is problematic with the black onyx board and the glass plate since its reflecting the red ir laser sometimes even reading the hotend temperature
i guess you should tinker with the beta value till its almost accurate
ill do the same today so ill report back later

Is that for me or bot?

Would I be better off taping a thermocouple from my DMM to the bed instead or using something else instead of the IR thermometer?

yes you would be much more accurate with a thermocouple however i would just get one of these temp feeler wires and tape them down with kapton
still for my needs the ir is good enough its 0.5C° off and i dont think that even matters.

[bot]

Which calculations are you wondering about? I just guessed at a beta value that brought my temps to a predictable and reasonable approximation of the temps on my rostock max. They aren't accurate, but I've gotten used to them.