Expected negative temperature rise

[benecito]

Never mind the error message and the fact that it is cut, but can someone please explain where a negative expected temperature rise is coming from?
Does duet monitor the falling temperature if the bed is i.e. at 100°C and is then set to 60°C?

Bed heater with "normal" PID values from an automatic tuning and firmware 3.4.6

[Phaedrux]

Where is that error message from? What printer?
What was the printer doing when you saw it?

[dc42]

@benecito I think that is the minimum temperature rise expected, which is the calculated expected temperature minus a tolerance. The message generated by RRF gives the measured temperature rise too but that part appears to have been truncated.

[benecito]

@dc42 If that's the case I will put all my duet printers into a self extinguishing cabinet right away. From my understanding this would mean a heater that might be at full power with no temperature rise will not trigger a heater fault?

The end is truncated because the printer is still on 3.4.6 where the maximum length of the string is limited and needs to be passe don to RepetierServer.

[dc42]

@benecito said in Expected negative temperature rise:

From my understanding this would mean a heater that might be at full power with no temperature rise will not trigger a heater fault?

That's correct, if all the following are true:

• you set a temperature that is too high for the heater to reach (which may depend on the print cooling fan speed)
• that temperature is lower than the temperature limit set by M143 (or the default if you didn't use M143 to set a temperature limit)
• you have run tuning on that heater, so RRF knows that it shouldn't expect a temperature rise at that temperature
• in heating up to that point, the measured temperature behaved in accordance with the model.