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  • Using a multimeter as a gaussmeter

    Hi!
    How is it possible ? I saw someone on youtube with a probe plugged into the fluke MM and comparing guitar magnets...
    Is it simple ?

  • #2
    Originally posted by tepsamps View Post
    Hi!
    How is it possible ? I saw someone on youtube with a probe plugged into the fluke MM and comparing guitar magnets...
    Is it simple ?
    Start by linking the YT video
    Juan Manuel Fahey

    Comment


    • #3
      The one I've seen.
      The probe converts gauss to MV.
      You are reading MV, and use a chart to convert MV readings to gauss.
      T


      "If Wishes Were Horses, Beggars Would Ride!" Scottish Proverb 1600s
      Terry

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      • #4
        Cool, now two have seen it
        Maybe, just maybe, one day Ill also be able to join the exclusive Club.
        Juan Manuel Fahey

        Comment


        • #5
          Originally posted by J M Fahey View Post
          Cool, now two have seen it
          Maybe, just maybe, one day Ill also be able to join the exclusive Club.
          There's loads of websites explaining how to do it using a cheap Hall sensor from alibaba. I did build my own some years ago but, honestly, my advice to the OP is just to buy a cheap Chinese gauss/telsa meter off Amazon for 100. There is no shortage of cheap options these days. I use the Isunking SJ200. It was 105 delivered. It comes with a wired probe and a hard case. If it gets broken or stolen I won't cry too hard..
          OP: no need to spend big on a gauss meter for alnico magnets. By all means build your own but if you have to ask how, rather than just google it in 20 seconds, I'm inclined to think you maybe should not waste your time with that ..

          Comment


          • #6
            I think MaarkusBass is manufacturing one.
            If so; Id much prefer to use one of his, where I can solve any doubts, ask for special calibration, whatever, than from an anonymous seller at the other end of the World.

            FWIW I must design and build one, , because I need to measure magnetic flux density in speaker magnetic gaps, which normal Gaussmeters can not do.

            Partly because typical values run from 10000 to 15000 Gauss (1 to 1.5 Tesla) which is well beyond usual Hall sensors, but even more because speaker gaps go from 0.9 to 1.3 mm wide and usual meters simply do not fit.

            To boot, speaker gaps are circular and small diameter (as small as 12mm or so) so I guess Ill have to custom build my own Hall sensor
            Juan Manuel Fahey

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            • #7
              I can't find back the video on youtube... My quest is no big deal, i was just to have an idea between different magnets...

              Comment


              • #8
                Magnet ("Hall") sensors are 3 or 4 lead devices requiring additional electronic to supply the constant lateral current.
                - Own Opinions Only -

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                • #9
                  FWIW I must design and build one, , because I need to measure magnetic flux density in speaker magnetic gaps, which normal Gaussmeters can not do.

                  Partly because typical values run from 10000 to 15000 Gauss (1 to 1.5 Tesla) which is well beyond usual Hall sensors, but even more because speaker gaps go from 0.9 to 1.3 mm wide and usual meters simply do not fit.

                  To boot, speaker gaps are circular and small diameter (as small as 12mm or so) so I guess Ill have to custom build my own Hall sensor
                  This is my AlphaLab Gauss meter. It measures up to 19,999G. The thickness of the probe is 1.3mm but I think it could be reduced by more than 0.5mm if the shrink tubing is replaced by thin tape:

                  Click image for larger version

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                  I bought it used on ebay and verified accuracy.
                  - Own Opinions Only -

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                  • #10
                    If my electronic gauss meters fail, I can always use the electromechanical one:

                    Click image for larger version

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                    Epoxied frame shaped coils of different sizes spinning at constant speed/rpm. Made in 1958.
                    - Own Opinions Only -

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                    • #11
                      Thanks.
                      I loved the electromechanical one

                      When no latest fad instrument is available, I always go back to the old Physics Lab basic instruments, after all the Masters (Maxwell, Gauss, etc.) *created* this branch of Physics without Electronics, let alone Computers, God forbid!!

                      I currently measure my speakers using a search coil coupled to a Ballistic Galvanometer ; only replacing the latter one with an OpAmp integrator and a sample and hold system (or measured value drifts away).

                      The search coil is simply the actual speaker coil I will use, and I must divide result by number of turns, easy thing to do.

                      My result is in Maxwells and I must divide this by gap surface to get average Gauss (or tesla)

                      So I manage to measure lots of stuff without modern or dedicated instruments but of course must add some conversion math to get the units I need.

                      Of course it would nice to have a thin probe and just insert it in a speaker gap, then read a display

                      I saw Gauss has a thin one, 0.8mm, but 3.7mm wide, not sure it will follow the curve of a small voice coil gap, I guess its rigid.

                      So again I will have to build my own custom probe, following old Physics Labs tricks .

                      Not sure Mr Hall had much access to semiconductors or computers, yet he *discovered* the Principle.
                      Juan Manuel Fahey

                      Comment


                      • #12
                        Originally posted by J M Fahey View Post
                        Cool, now two have seen it
                        Maybe, just maybe, one day Ill also be able to join the exclusive Club.
                        Just search for 'diy gaussmeter'.
                        http://guitarfix.dk

                        Comment


                        • #13
                          Originally posted by J M Fahey View Post
                          Cool, now two have seen it
                          Maybe, just maybe, one day Ill also be able to join the exclusive Club.
                          If you have too much spare time, DIY gaussmeters got a minor smacking-around
                          in the 2010 thread Yet Another Gaussmeter

                          -hizself
                          He who moderates least moderates best.

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                          • #14
                            Thanks a lot, but most posted gaussmeters are useless to me.

                            In general they measure up to 3K or 4K Gauss and measure surface magnetism, so perfect for pickup use.

                            I need to measure loudspeakers, typical values between 10k and 15k Gauss (way above saturation point for any Hall sensor I found) and inside down to 0.8mm gaps in loudspeakers, where to boot path is curved and voice coils can be as small as 12mm diameter.

                            So the main problem is the sensor, both in sensitivity and size.

                            Having a suitable one; the Electronics side can be handled.

                            Thanks anyway.
                            Juan Manuel Fahey

                            Comment


                            • #15
                              Originally posted by J M Fahey View Post
                              Thanks a lot, but most posted gaussmeters are useless to me.
                              Juan Manuel, no rompas ms las pelotas, quers?

                              No translation for the above statement will be provided.

                              Por supuesto, estoy bromeando, hermano.

                              Que las pases bien!

                              Tu compatriota,

                              Pepe
                              Pepe aka Lt. Kojak
                              Milano, Italy

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