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Z Home - Multiple probe average

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IR Height Sensor
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  • undefined
    dm86
    last edited by 5 Mar 2021, 17:17

    Hi all,

    I'm getting fairly variable reads using the IR sensor on glass.

    Is there an example anywhere of taking multiple reads and averaging them out? I can't seem to find it but maybe I'm searching thewrong terms.

    Thanks

    undefined 1 Reply Last reply 5 Mar 2021, 17:24 Reply Quote 0
    • undefined
      Veti
      last edited by 5 Mar 2021, 17:19

      see
      https://miscsolutions.wordpress.com/mini-height-sensor-board/

      Glass (with or without coatings such as hairspray, PVA or Kapton tape): works as-is if placed directly on a PCB bed heater or other surface that does not reflect strongly. If there is an aluminium heat spreader or bed plate underneath the glass, then either paint the aluminium surface matt black (see below), or put a sheet of matt black paper between the glass and the aluminium. Coatings on the glass affect the trigger height slightly.

      undefined 2 Replies Last reply 6 Mar 2021, 00:29 Reply Quote 1
      • undefined
        fcwilt @dm86
        last edited by 5 Mar 2021, 17:24

        @dm86 said in Z Home - Multiple probe average:

        Hi all,

        I'm getting fairly variable reads using the IR sensor on glass.

        Is there an example anywhere of taking multiple reads and averaging them out? I can't seem to find it but maybe I'm searching thewrong terms.

        Thanks

        Here is my Z probe M558 command:

        M558 K0 P8 C"!io8.in" H2 F300 T9000 R0.2 A10 S0.01

        Notice the A and S parameters.

        If you used A5 S-1 you would take 5 readings and they would then be averaged.

        Frederick

        Printers: a small Utilmaker style, a small CoreXY and a E3D MS/TC setup. Various hotends. Using Duet 3 hardware running 3.4.6

        undefined 1 Reply Last reply 5 Mar 2021, 17:46 Reply Quote 1
        • undefined
          dm86 @fcwilt
          last edited by 5 Mar 2021, 17:46

          @fcwilt Thanks, totally missed that. For some reason was expecting it to be on G30.

          1 Reply Last reply Reply Quote 0
          • undefined
            dm86 @Veti
            last edited by 6 Mar 2021, 00:29

            @Veti I have my bed on a blue silicon thermal transfer pad which gives a really good backing for the sensor. I've been using it well for quite a while but I've found these sensors lose accuracy after a while. I've always assumed its the cap drying out but never really investigated.

            Multiple probes seems as easy way to get a little extra life before replacing.

            1 Reply Last reply Reply Quote 0
            • undefined
              dm86 @Veti
              last edited by 6 Mar 2021, 00:31

              @Veti Thanks again Frederick, got it working now. However I couldn't find reference to the S-1 command anywhere, do you know where this is documented?

              The GCODE Library just appears to just say,
              "Snnn Tolerance when probing multiple times, default 0.03mm".

              Does -1 just force the max number of probes?

              undefined undefined 2 Replies Last reply 6 Mar 2021, 00:57 Reply Quote 0
              • undefined
                fcwilt @dm86
                last edited by 6 Mar 2021, 00:57

                @dm86 said in Z Home - Multiple probe average:

                @Veti Thanks again Frederick, got it working now. However I couldn't find reference to the S-1 command anywhere, do you know where this is documented?

                The GCODE Library just appears to just say,
                "Snnn Tolerance when probing multiple times, default 0.03mm".

                Does -1 just force the max number of probes?

                It may not be documented as such but it follows from what S determines.

                The probing continues until two consecutive readings are within the S value.

                What are the odds that two readings are going to be within -1?

                Frederick

                Printers: a small Utilmaker style, a small CoreXY and a E3D MS/TC setup. Various hotends. Using Duet 3 hardware running 3.4.6

                1 Reply Last reply Reply Quote 0
                • undefined
                  Phaedrux Moderator @dm86
                  last edited by 6 Mar 2021, 03:29

                  @dm86 said in Z Home - Multiple probe average:

                  I couldn't find reference to the S-1 command anywhere

                  The A and S parameters control multiple probing. Probing is repeated until two consecutive probe attempts produce results that differ by no more than the S parameter; then the average of those two results is used. However, if the number of attempts specified by the A parameter is reached without getting two consecutive results within tolerance of each other, no further probe attempts are made and the average result of all the attempts is used.

                  I guess it's kind of hidden in that paragraph. I should add a note in there about using S-1 to force the averaging.

                  Z-Bot CoreXY Build | Thingiverse Profile

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