Thermistor spikes



  • I am experiencing large temperature read-out spikes. My machine is a Rostock Max V3 with a stock hotend/heater, so temps are read with a Semitec GT-104 thermistor.

    The spikes have only occurred during longer prints (or multiple consécutive small prints) after about ~3 hours. Resetting with a M562 P1 immediately fixes the issue. This makes me believe that my issue is not related to expansion/contracting of connections due to heat.

    Advice is very much welcome. If any tests need to be conducted or extra info is needed, let me know.


  • administrators

    Do you mean you are seeing large positive-going temperature spikes? If so, then with a thermistor as the temperature measuring device, that suggests an intermittent short circuit in the wiring.



  • That is correct, large positive spikes. I was thinking about a short as the reason, but I can not see why it would only occur during long prints (maybe just luck?) if not due to expansion from heat. But then I don't understand how a simple reset fixes this.


  • administrators

    A spike that persists for a little while will trigger a heater fault even if the spike doesn't persist for long. Sending M562 P1 resets the heater fault.


  • administrators

    @Nxt-1:

    That is correct, large positive spikes. I was thinking about a short as the reason, but I can not see why it would only occur during long prints (maybe just luck?) if not due to expansion from heat. But then I don't understand how a simple reset fixes this.

    A possibility is that on a long print the head moves to part of the builds space (higher)? that you don't use on shorter prints? it could be that a cable is partly broken inside causing intermittent connections only when moved in a specific area of the build space.

    You might be able to confirm this by driving the print head around your build space to the extremes while wiggling the cables by hand to see if you can reproduce the spikes.


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