PT100 hotend temp value difference with heated bed value.

Discussion in 'Calibration, Help, and Troubleshooting' started by moshen, Jul 18, 2016.

  1. moshen

    moshen Well-Known Member

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    Are you guys seeing similar temps for both the hotend and the heated bed? On mine, my heated bed is consistently 3-4 degrees C higher than the hotend when at rest. I don't expect it to match perfectly but my other printers are closer. I'm wondering if this is an anomaly with me or others seeing it. Perhaps some tweaking some firmware constants can get them closer...
     
  2. Alex9779

    Alex9779 Moderator
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    You mean if they are at room temperature?
     
  3. Alex9779

    Alex9779 Moderator
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  4. moshen

    moshen Well-Known Member

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    Yes room temperature. Right now my Hotend reads 18.7C, Bed 22.1C.
     
  5. Alex9779

    Alex9779 Moderator
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    Hmmmm according to my picture it is not the case for me. But I can confirm that the temperature graphs seem more unstable to me at low temperatures compared to when the hotness and the bed are heated...
     
  6. elmoret

    elmoret Administrator

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    There's little accuracy/resolution on a 3D printer's thermistor at low temperatures, due to the nonlinear response.

    OP: nothing to worry about, print on!
     
  7. fpex

    fpex Well-Known Member

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    Makes no difference. I have used a Duet0.6 with expansion and its ground plane error intruding a rather unstable low temp behaviour and it had zero effects on printing.
     
  8. Dr Jeep

    Dr Jeep Well-Known Member

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    elmoret, the PT100 probes I am used to dealing with are pretty much linear. I think I have either a problem with the amp or the lack of screened cable is killing me (any word from E3D yet as to why they changed from a screened cable ? ) Last night it was jumping about over 5 degrees (on the rumba and octoprint) and I took the time to see if disabling steppers etc had any effect. Does seem worse at lower temps but if it is interference based then that makes perfect sense as the noise will be a bigger percentage of the signal.

    Work is mad at the moment so not had time to get test equipment hooked up, I might ask E3D if I can try another PT100 amp as that flat line in the cooldown looks dodgy.

    At least I have proven it's not PID

    In the graph below the first cooldown was after a print and then after I heated it up again and did a filament change.

    [​IMG]
     

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