Duet3D Logo Duet3D
    • Tags
    • Documentation
    • Order
    • Register
    • Login

    PT1000 inaccurate readings at higher temps

    Scheduled Pinned Locked Moved
    Duet Hardware and wiring
    3
    10
    1.3k
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • jckrayundefined
      jckray
      last edited by jckray

      I have a K type for the heat bed and a pt1000 for the hotend. At room temp they measure the temp within .4 degs of each other and are also within about 1 deg of an external k type thermometer.

      The problem arises when heating up to printing temps. The pt1000 reads 240C, but when measuring the temp with the k type thermometer at the heater block I'm getting 260C. Compared to using a pt100 where I measured 230C at the heater block when the pt100 was reading 240C. This is also evident during printing. Swapping between the pt100 and pt1000 both reading 240C, the parts printed with the pt1000 show significant signs of being printed too hot.

      I have seen that you can tune the pt1000 with the M305 L and parameter, but that is for tuning readings at low temps. If I modify the L parameter to read correctly at 240C then the room temp reading is off.

      Any idea what is going on?

      John
      Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
      https://www.hydraresearch3d.com/

      dc42undefined 1 Reply Last reply Reply Quote 0
      • dc42undefined
        dc42 administrators @jckray
        last edited by

        @jckray said in PT1000 inaccurate readings at higher temps:

        Compared to using a pt100 where I measured 230C at the heater block when the pt100 was reading 240C.

        Please explain what you mean.

        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

        1 Reply Last reply Reply Quote 0
        • jckrayundefined
          jckray
          last edited by

          @dc42 I used a separate thermometer to measure the temperature on the heater block right where the nozzle on a V6 joins the heater block. Now I realize that this might give a different reading than the cartridge sensor embedded in the block, but if both the pt100 and pt1000 are reporting the same temperature, I would think that the thermometer would measure reasonable close to the same temperature for both.

          However, with a set temp of 240C for both the pt100 and pt100 I measured drastically different temps with the thermometer. The pt100 would read 240C but the thermometer measuring the temp on the outside of the heater block would measure 230C. Not, necessarily a problem, I wouldn't expect them to read the same thing, but they should be fairly close.

          The same test with the pt1000 yielded temps of 260C measured with the thermometer on the outside of the heater block.

          What I'm saying I'm experiencing a 30C variance in the measured temperature and the actual temperature between the pt100 and pt1000.

          Sorry if this is a little confusing.

          John
          Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
          https://www.hydraresearch3d.com/

          PuterProundefined 1 Reply Last reply Reply Quote 0
          • dc42undefined
            dc42 administrators
            last edited by

            Which type of Duet is this?

            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

            1 Reply Last reply Reply Quote 0
            • PuterProundefined
              PuterPro @jckray
              last edited by

              @jckray said in PT1000 inaccurate readings at higher temps:

              Now I realize that this might give a different reading than the cartridge sensor embedded in the block,

              Offhand, I'd want to insulate the PT100 on the outside as a good deal of it's surface area is exposed to air, unlike the embedded sensor. If you had some of that cotton batting & Kapton tape you could temporarily wrap it around the outside of the whole thing. I think you might get a more accurate reading.

              That said, I have a PT1000, and when I first set it up I used a K-Type bead hooked to a bench multimeter (pretty accurate) and found some differences as well. PID Tuning handled it.

              The discussion was here: https://forum.duet3d.com/topic/9445/temp-woes-continue
              (the "continue" part was I had a config problem the day before that was strictly my fault)

              1 Reply Last reply Reply Quote 0
              • jckrayundefined
                jckray
                last edited by

                @dc42 I'm using the Duet 2 WiFi rev 1.04b.

                @PuterPro Thanks, I will check out that thread.

                Since my last post, I was able to achieve reasonable results using the M305 L and H parameters. Not sure if this is the best solution, but if it works... I had to use L10 H-120.

                John
                Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
                https://www.hydraresearch3d.com/

                dc42undefined 1 Reply Last reply Reply Quote 0
                • dc42undefined
                  dc42 administrators @jckray
                  last edited by dc42

                  @jckray said in PT1000 inaccurate readings at higher temps:

                  @dc42 I'm using the Duet 2 WiFi rev 1.04b.

                  @PuterPro Thanks, I will check out that thread.

                  Since my last post, I was able to achieve reasonable results using the M305 L and H parameters. Not sure if this is the best solution, but if it works... I had to use L10 H-120.

                  Are you able to do some tests using fixed resistors in place of the PT1000, and compare the firmware readings against the values in a PT1000 resistance vs. temperature table? The H and L parameters are normally needed only on the older Duets; and H-120 is an extreme value.

                  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

                  1 Reply Last reply Reply Quote 0
                  • jckrayundefined
                    jckray
                    last edited by

                    @dc42 I certainly can. Do you happen to know where I can find said table?

                    John
                    Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
                    https://www.hydraresearch3d.com/

                    dc42undefined 1 Reply Last reply Reply Quote 0
                    • dc42undefined
                      dc42 administrators @jckray
                      last edited by

                      @jckray, a web search will turn up lots of them. Here's one https://www.sterlingsensors.co.uk/pt1000-resistance-table.

                      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

                      dc42undefined 1 Reply Last reply Reply Quote 0
                      • dc42undefined
                        dc42 administrators @dc42
                        last edited by dc42

                        PS - I just did some tests on the Duet WiFi on my bench:

                        1K resistor reads -2.7C to -3.0C. It should be 0.0C, so if my resistors are accurate then it is under-reading by almost 3C.

                        2K resistor reads 266.9 to 267.6C. It should be 266.3C, so if my resistor is accurate then it is over-reading by about 0.5C.

                        These are with zero L and H correction. I then tried the same resistors on a Duet Maestro:

                        1K gave -0.8 to -1.0C (under reading by 0.9C)
                        2K gave 270.3 to 270.7C (over reading by 4.2C)

                        The Maestro can measure PT1000 sensors more accurately. I think I may be able to improve on the error at low temperatures on the Duet WiFi.

                        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

                        1 Reply Last reply Reply Quote 0
                        • First post
                          Last post
                        Unless otherwise noted, all forum content is licensed under CC-BY-SA