e3d pt100 radds and repetier - temps to low

Hi Guys,

I use the e3d pt100 in combination with the radds board. My problem is, that the tempsvalue are to low. At 21° C room temperature the display shows 1° C and the bed 21°. So the reading of the pt100 is to low. When i than heat the nozzel up the temps are rising but it seems like the showen temp is much lower than the real one of the nozzle. Can i adjust that or do something else?

best reagards


  • pt100 on radds might need a different scale. Check extruder.cpp for pt100 - there is a switch to use a different voltage multiplyer (scaled for 3.3v) and it might use the wrong one there.
  • Thank you for the fast answer. I can't find that "switch" in extruder.cpp. What do i have to search for? I also can't find the table for the e3d temp table.

    best regards
  • Sorry, I mixed the types. I meant this

        case 61: // AD8495 1.25V Vref offset (like Adafruit 8495 breakout board)

    #if CPU_ARCH == ARCH_AVR

            currentTemperatureC = ((float)currentTemperature * 1000.0f / (1024 << (2 - ANALOG_REDUCE_BITS))) - 250.0f;


            currentTemperatureC = ((float)currentTemperature * 660.0f / (1024 << (2 - ANALOG_REDUCE_BITS))) - 250.0f;


    But PT100 is a fixed PTC. Here the question is did you use the e3d ampilfier and where did you connect it to? The thermocouple pins are in series with 4.7k resistor so you can not use them. You need the analog input at the long side for this.

  • I connected it to the analog pin on the long side of the radds board. And yes i use the e3d ampilfier. I found Out that i don't have stable 5v source, it has only 4,6 v. The solution is a little buck boost converter to get stable 5v. Now everything ist fine. Thanks for your Help.

    Best regards
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