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Any way to offset PT100 temp setting beside running more wires?

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  • undefined
    briangilbert
    last edited by 1 Apr 2018, 04:37 4 Jan 2018, 00:52

    I've just installed an E3D PT100 and using their supplied wires, unfortunately the temp reading is around 8degrees higher than my bed thermistor at room temp.

    Is there any way to correct temp reading without running extra wires?

    Co-creator of the Zesty Nimble direct drive extruder

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    • undefined
      dc42 administrators
      last edited by 4 Jan 2018, 07:52

      Use thicker wires?

      To get an error of 8C you must have about 3 ohms resistance in the connections to the PT100. Perhaps you have a bad connection?

      Duet WiFi hardware designer and firmware engineer
      Please do not ask me for Duet support via PM or email, use the forum
      http://www.escher3d.com, https://miscsolutions.wordpress.com

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      • undefined
        DjDemonD
        last edited by 4 Jan 2018, 13:19

        The offset feature is a great idea, I've taken to measuring the nozzle temp with K type thermocouple probe and thermal paste and using the offset to adjust to real nozzle temp.

        Simon. Precision Piezo Z-Probe Technology
        www.precisionpiezo.co.uk
        PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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        • undefined
          briangilbert
          last edited by 5 Jan 2018, 19:52

          @dc42 I've changed over to a different PT100 and am still getting a high (but lower reading), would it be possible to add an offset feature?

          Co-creator of the Zesty Nimble direct drive extruder

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          • undefined
            DjDemonD
            last edited by 1 May 2018, 20:09 5 Jan 2018, 20:08

            Its already there Brian add an R parameter to M305 for that pt100 which is the series resistor value, this effectively offsets it. I've been measuring nozzle temp then adjusting it on the fly to match:

            M305 P1 X201 R400 ; temp channel config, heater 1, PT100 sensor 2, offset

            A higher R value will raise the indicated temp, a lower one will lower it. Only small adjustments are necessary.

            Simon. Precision Piezo Z-Probe Technology
            www.precisionpiezo.co.uk
            PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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            • undefined
              dc42 administrators
              last edited by 5 Jan 2018, 21:14

              If the error is caused by the PT100 resistance being out of tolerance (i.e. a bit more than 100 ohms), then adjusting the R parameter will correct for it - but it suggests you are using a very low-quality PT100 sensor. However, if the error is caused by additional resistance in your wiring or connectors, then correcting it using the R parameter will cause the PT100 to under-read somewhat at higher temperatures.

              Duet WiFi hardware designer and firmware engineer
              Please do not ask me for Duet support via PM or email, use the forum
              http://www.escher3d.com, https://miscsolutions.wordpress.com

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              • undefined
                totalitarian
                last edited by 1 May 2018, 23:41 5 Jan 2018, 23:40

                I bought one from Precision Piezo and it seems to be measuing the same value as my bed so i'm happy.

                DjDemonD I don't suppose you sell even longer ones? I need roughly 100mm more. Very large corexy build.

                dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

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                • undefined
                  garyd9
                  last edited by 5 Jan 2018, 23:46

                  @totalitarian:

                  dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

                  Doesn't it come with a little plastic standoff that snaps into the hole on the daughter board and hole on the duet board? (My thermocouple daughter board came with something like this.)

                  "I'm not saying that you are wrong - I'm just trying to fit it into my real world simulated experience."

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                  • undefined
                    DjDemonD
                    last edited by 1 May 2018, 23:56 5 Jan 2018, 23:51

                    @totalitarian:

                    I bought one from Precision Piezo and it seems to be measuing the same value as my bed so i'm happy.

                    DjDemonD I don't suppose you sell even longer ones? I need roughly 100mm more. Very large corexy build.

                    dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

                    I don't do a longer lead version but make a linesman's splice joint and solder it, with good quality wire and you can extend it. You can always compensate it a little using the R parameter as above.

                    Simon. Precision Piezo Z-Probe Technology
                    www.precisionpiezo.co.uk
                    PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                    • undefined
                      dc42 administrators
                      last edited by 6 Jan 2018, 06:45

                      @totalitarian:

                      dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

                      Yes, a plastic standoff is included with each daughter board.

                      Duet WiFi hardware designer and firmware engineer
                      Please do not ask me for Duet support via PM or email, use the forum
                      http://www.escher3d.com, https://miscsolutions.wordpress.com

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                      • undefined
                        totalitarian
                        last edited by 7 Jan 2018, 09:47

                        @DjDemonD:

                        @totalitarian:

                        I bought one from Precision Piezo and it seems to be measuing the same value as my bed so i'm happy.

                        DjDemonD I don't suppose you sell even longer ones? I need roughly 100mm more. Very large corexy build.

                        dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

                        I don't do a longer lead version but make a linesman's splice joint and solder it, with good quality wire and you can extend it. You can always compensate it a little using the R parameter as above.

                        Thanks, i'll give that a go.

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                        • undefined
                          totalitarian
                          last edited by 7 Jan 2018, 10:49

                          @dc42:

                          @totalitarian:

                          dc42, shouldn't there be a leg/support/standoff with the daughter board? It seems a little fragile unsupported…

                          Yes, a plastic standoff is included with each daughter board.

                          I'll have to take a look, I never noticed a standoff with mine.

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