PT100 shows 80°C at room temperature

Discussion in 'E3D-v6 and Lite6' started by ChrisK, Jan 12, 2018.

  1. ChrisK

    ChrisK Member

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    I have build a HyperCube 3D Printer (RAMPS-Based) with E3D V6 HotEnd and a PT100 Sensor and Amplifier, but the shown temperature is to high! Pronterface shows 80°C instead of around 20°C room temperature (unheated, Arduino Mega 2560 is only conected by USB).

    Marlin 1.1.8 is configured as shown in E3D documentation ('#define TEMP_0_PIN 3' in pins_RAMPS.h and '#define TEMP_SENSOR_0 20' in Configuration.h).

    So what's wrong?

    Thanks
     
  2. Ephemeris

    Ephemeris Well-Known Member

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    Double check you don't have a really bad connection to the PT100. An extra 20 ohms in your leads and connectors would cause it to read high by 60C.

    Turn off all the power to the printer then do a resistance check. Disconnect the PT100 leads from the PT100 board and measure the PT100 resistance with a meter. If it's around 108 ohms, the PT100 is not the problem and it's either the the PT100 board or a software issue. If it reads around 131 ohms, there's something wrong in the PT100 or your wiring.
     
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  3. ChrisK

    ChrisK Member

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    Thanks for the feedback, I'll check that! :)
     
  4. ChrisK

    ChrisK Member

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    Hi Ephemeris,

    my multimeter shows a risistance of 126.8 kOhm directly at the thermistor connector, without extra wiring.
    And the voltage of the PT100 Amplifier Board (Signal to Ground) shows 1.42V (with or without the connected thermistor) instead of 1.2V (like John from E3D [Mail] said).

    That's strange!

    Do I really have such luck that probably the thermistor and the amplifier board are broken?
     
  5. Ephemeris

    Ephemeris Well-Known Member

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    If that's a PT100 it's totally broken. On the other hand, that resistance is what a thermistor might read.

    Read THIS

    It says a 104GT thermistor reads 126.8k ohms at 20C. SOmehow you've got a thermistor instead of PT100 sensor.
     
  6. ChrisK

    ChrisK Member

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