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  • Measuring inductance with standard multimeter

    I have a standard multimeter with an (supposedly) inductance meter position.
    However I cannot get the inductance of any pickup with this. I believe this is "normal" since this is true for any pup I've tried to get the value.
    Could someone give me the clue why this ? I suppose I'd need a proper LRC meter for this task, right? (But why then having an inductance meter on the multimeter if useless...is this just a crappy tool?)

    Thanks,
    Yves
    www.bourvonaudiodesign.fr

  • #2
    Joe Gwinn's explanation

    Comment


    • #3
      ....

      It probably doesn't have a proper test signal, for pickups you need 1khz and 120hz. I was just looking over some cheap inductance meters and they have a 20khz test signal, totally useless for pickups. Yes you should be a good LCR meter, the Extech is good because it has those two test frequencies plus it also measures AC resistance which I find really useful. They're not cheap but oh well, what is.....
      http://www.SDpickups.com
      Stephens Design Pickups

      Comment


      • #4
        also, might be beyond the range of inductance it can read

        Comment


        • #5
          Thanks for the info, all of you.
          BTW, and having read Joe Gwin's explanation, I am surprised to learn that a B&K meter would not do the job :I would have expect such meter to be a reliable tool (in any situation).
          So Extech is on my list now when I have the money for it.
          www.bourvonaudiodesign.fr

          Comment


          • #6
            You still need the VOM though, so it wont go to waste.
            It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein


            http://coneyislandguitars.com
            www.soundcloud.com/davidravenmoon

            Comment


            • #7
              Cheap LCR meter

              I've just bougth the Elektor issue of June: there is an very simple, cheap LCR meter using a PC sound card.

              I cannot reproduce the article here for obvious copyright reason, but you've got the info for those of you who are not equipped with this tool, if you want to buy the issue.

              Altenatively, here is the link to the article:
              http://www.elektor.com/magazines/200...0.495109.lynkx

              I think that if you register, you get 10 units free credits (at least this is the case in the FR site), which is just enough to download the article in pdf.

              I have not tested it yet since I need to buy one IC for this first (need to find the time), so now feedback for the moment ...

              Yves.
              www.bourvonaudiodesign.fr

              Comment


              • #8
                Originally posted by Yves View Post
                I've just bougth the Elektor issue of June: there is an very simple, cheap LCR meter using a PC sound card.

                I cannot reproduce the article here for obvious copyright reason, but you've got the info for those of you who are not equipped with this tool, if you want to buy the issue.

                Altenatively, here is the link to the article:
                http://www.elektor.com/magazines/200...0.495109.lynkx

                I think that if you register, you get 10 units free credits (at least this is the case in the FR site), which is just enough to download the article in pdf.
                And flood one with valuable free offers.

                I have not tested it yet since I need to buy one IC for this first (need to find the time), so now feedback for the moment ...
                What is the basic measurement being made? This will help tell if the instrument can handle pickups, which have a large amount of DC resistance in series with the inductance. Most LCRs give wildly wrong answers on pickups.

                My guess is that this sound-card based instrument will not work well with pickups for a very fundamental reason: sound cards ignore phase and measure only amplitude. For a sound card, this is reasonable, because the human ear does not sense phase either, and certainly does not care about relative phase between input and output.

                To measure LCR, phase is essential unless the component being tested is very "pure" (so one letter always predominates). But in pickups, the R and L have about the same reactance at the frequencies of interest, and thus are quite impure.

                Comment


                • #9
                  Originally posted by Yves View Post
                  I've just bougth the Elektor issue of June: there is an very simple, cheap LCR meter using a PC sound card.
                  An afterthought. If you have the PC sound card, you can use it to drive a Maxwell Bridge.

                  http://home.comcast.net/~joegwinn/

                  This can be very accurate, and will work at any frequency, but is slow to use. I used this bridge to validate the Extech, to prove that it gave full accuracy on real pickups.

                  If you will measure many coils, get the Extech.

                  Comment


                  • #10
                    If available, check out a Lutron

                    Hi,
                    for LCR measurements I purchased a Lutron LCR meter, it' s reliable, quite accurate and it could fit the bill without hurting your wallet that much; what' s best, it reads inductances up to 20 H, way over the hottest imaginable overwound pickup, and the capacitance meter goes up to 2000 mF, so I also use it to sort out caps on tube amps' PS filtering sections. I got it for about 100 Euros, check if this brand is available in your area.
                    Regards
                    Bob
                    Hoc unum scio: me nihil scire.

                    Comment


                    • #11
                      smiling phases

                      Originally posted by Joe Gwinn View Post
                      the human ear does not sense phase either, and certainly does not care about relative phase between input and output.
                      We sense ear-to-ear differential phase best when the full wave length is roughly the length of our ear canal. Absolute phase is, of course, impossible.

                      -drh
                      "Det var helt Texas" is written Nowegian meaning "that's totally Texas." When spoken, it means "that's crazy."

                      Comment


                      • #12
                        Originally posted by voxrules! View Post
                        Hi,
                        for LCR measurements I purchased a Lutron LCR meter, it' s reliable, quite accurate and it could fit the bill without hurting your wallet that much; what' s best, it reads inductances up to 20 H, way over the hottest imaginable overwound pickup, and the capacitance meter goes up to 2000 mF, so I also use it to sort out caps on tube amps' PS filtering sections. I got it for about 100 Euros, check if this brand is available in your area.
                        What's the exact model number? I'd like to look it up.

                        Comment


                        • #13
                          Originally posted by salvarsan View Post
                          We sense ear-to-ear differential phase best when the full wave length is roughly the length of our ear canal. Absolute phase is, of course, impossible.
                          But...but...between ears is between inputs....

                          Comment


                          • #14
                            Originally posted by Joe Gwinn View Post
                            But...but...between ears is between inputs....
                            I merely wanted to point out that the auditory mechanism by itself does interesting preprocessing.

                            Those three bones that couple the drum to the cochlea perform a rough differentiation and half-wave rectification before the signal ever gets to the cochlea.

                            ...then there's all that pre and post compensation that the limbic system adds.

                            Oy.

                            Wish there was a calibration run that we could do on ears
                            before we start yakking about pickup timbre.

                            If there was more money in it, pickup making would have what
                            Emile Peynaud types and UC Davis did for wine.

                            -drh
                            "Det var helt Texas" is written Nowegian meaning "that's totally Texas." When spoken, it means "that's crazy."

                            Comment


                            • #15
                              Originally posted by salvarsan View Post
                              I merely wanted to point out that the auditory mechanism by itself does interesting preprocessing.

                              Those three bones that couple the drum to the cochlea perform a rough differentiation and half-wave rectification before the signal ever gets to the cochlea.

                              ...then there's all that pre and post compensation that the limbic system adds.
                              Yes. I read up on how bat sonar works some time ago. Very interesting - some species of bat do fixed-frequency pulses with doppler processing (to detect tiny movements despite obscuring vegetation) while other species use linear-chirp signals and pulse compression (to achieve very high range resolution and the ability to see very small targets far away). These are called CW (continuous wave) and FM (frequency modulation) respectively.

                              Present-day radars and sonars do almost exactly these things. The biggest difference is that radars and sonars are phase coherent, where the received signal is compared in phase with the transmitted signal. No animal does this.

                              However, bats anticipated the development of radar and sonar in WW2 by 60 million years.

                              Comment

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