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    #1

    How does this analog ESR meter work?

    Okay the title isn't exactly what I wanted to say, but I didn't want to make it too long.

    http://members.shaw.ca/swstuff/esrmeter.html

    Perhaps some of you have seen this meter. I'd like to build it because the part cost is very low, and hopefully will give me a general idea about the condition of caps etc. Thought it might be fun to build/have.



    So...I'm looking at the finished product in the enclosure. The analog gauge: Why are there no numbers on it? It just says bad or good? Also, why does it say 1uF in the middle of the good section?

    So is this meter strictly made to test whether it is good or bad? How does it really know? ESR can differ from cap to cap...

    Has anyone made one? Did you put numbers on it?

    Thanks.
    Tags: None
    #2
    Re: How does this analog ESR meter work?

    That kind of tester isn't of much use for low ESR caps. There are no numbers because he didn't bother to calibrate it, it's likely that he just measured several caps and made the gauge based on that.
    Originally posted by PeteS in CA
    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
    A working TV? How boring!

    Comment

      #3
      Re: How does this analog ESR meter work?

      Agree.
      Those are intended for testing GP caps.
      The range doesn't go low enough for low ESR caps.
      Useful tool, just not for Low ESR caps.
      .
      Mann-Made Global Warming.
      - We should be more concerned about the Intellectual Climate.
      -
      Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
      - Dr Seuss
      -
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      Comment

        #4
        Re: How does this analog ESR meter work?

        The knob is a zero adjust. So short the probes and adjust it for full scale before testing caps.

        Accuracy... well, I've built that one and used to to find bad low-ESR caps. It gives a relative value, not a number. The printed scale is probably a mistake, it's all relative. For positives, it has input protection, which is lacking on some ESR meters. It's easy to build, too.

        Comment

          #5
          Re: How does this analog ESR meter work?

          Originally posted by jsog View Post
          The knob is a zero adjust. So short the probes and adjust it for full scale before testing caps.

          Accuracy... well, I've built that one and used to to find bad low-ESR caps. It gives a relative value, not a number. The printed scale is probably a mistake, it's all relative. For positives, it has input protection, which is lacking on some ESR meters. It's easy to build, too.
          I never did anything with analog meters. What is zero adjust....

          So if I want to actually see the ESR, do I have to plug it into my DMM or something? Is it possible to get an ESR readout on the analog display?

          Is that possible? I'm not sure exactly how this one works..

          Thanks!
          Last edited by TheLaw; 07-29-2011, 10:54 AM.

          Comment

            #6
            Re: How does this analog ESR meter work?

            Analog meters have a "zero adjust" potentiometer which adjust the needle deflection to the precise end of scale point. If not set properly, the needle can overshoot or even not reach the end of scale.
            Yes, it is possible to read ESR in ohms, but needs to be calibrated against a known meter. This is not so easy because analog meters have a logarithmic scale.

            Comment

              #7
              Re: How does this analog ESR meter work?

              In order for that meter to be of any value, where the needle sits in the picture would have to be 0.10Ω and at the word "Good" would have to be 0.01Ω. It is not.

              Save your pennies, buy the Blue ESR meter by Bob Parker. Worth every cent.

              .
              veritas odium parit

              Comment

                #8
                Re: How does this analog ESR meter work?

                So I can't just get a 0.001ohm resistor and hook it up and see where it lands?

                This is going to sound dumb also, but there's no way I can get ESR readout by inputing into the resistance function on a DMM right?

                So this is mostly just a "good" or "bad" meter..which I guess serve's it's purpose.

                Comment

                  #9
                  Re: How does this analog ESR meter work?

                  Yes you can use a low ohms resistor to "see where it lands", but you're not going to be able to tell a reading of 0.06Ω (fail) from 0.02Ω (good). The scale is not "fine" enough.

                  ESR meters generate a frequency to test the cap. They are not "really" ohmmeters like you are thinking.

                  You'll not be able to distinguish between a good or bad unless it's -really- bad.

                  .
                  veritas odium parit

                  Comment

                    #10
                    Re: How does this analog ESR meter work?

                    Originally posted by Toasty View Post
                    Yes you can use a low ohms resistor to "see where it lands", but you're not going to be able to tell a reading of 0.06Ω (fail) from 0.02Ω (good). The scale is not "fine" enough.

                    ESR meters generate a frequency to test the cap. They are not "really" ohmmeters like you are thinking.

                    You'll not be able to distinguish between a good or bad unless it's -really- bad.

                    .
                    Hmmph. I see. Well I can probably make one for like $20, so I might just try it for the heck of it. I guess a digital one would be better in the end...but as a project, this seems pretty interesting.
                    Last edited by TheLaw; 07-29-2011, 01:39 PM.

                    Comment

                      #11
                      Re: How does this analog ESR meter work?

                      NJ

                      What Exit?

                      I'm TP #3
                      veritas odium parit

                      Comment

                        #12
                        Re: How does this analog ESR meter work?

                        The schematic shows pretty well what is going on. You could replace the meter with a DMM set to DC volts, but would have to calculate backwards from calibration values to get ohms.

                        Comment

                          #13
                          Re: How does this analog ESR meter work?

                          Originally posted by Toasty View Post
                          NJ

                          What Exit?

                          I'm TP #3
                          Exit 16.

                          Comment

                            #14
                            Re: How does this analog ESR meter work?

                            Originally posted by TheLaw View Post
                            So I can't just get a 0.001ohm resistor and hook it up and see where it lands?

                            This is going to sound dumb also, but there's no way I can get ESR readout by inputing into the resistance function on a DMM right?

                            So this is mostly just a "good" or "bad" meter..which I guess serve's it's purpose.
                            It takes a certain amount of current to get the needle to move.
                            -
                            To get a usable range for low ESR caps with that kind of meter you would have to drive the meter with an amp which would create more error than what you are trying to measure in the first place.
                            .

                            In a digital meter the current is measured by an IC so not much is needed.
                            The measurement is then digitized and sent to the display.
                            The display itself is not part of the measurement circuit.
                            .
                            Last edited by PCBONEZ; 07-29-2011, 05:29 PM.
                            Mann-Made Global Warming.
                            - We should be more concerned about the Intellectual Climate.
                            -
                            Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
                            - Dr Seuss
                            -
                            You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                            -

                            Comment

                              #15
                              Re: How does this analog ESR meter work?

                              Ohhhh I get it now.

                              Alright. Well I can build one for like $20, so I might just try it for poops and giggles.

                              Comment

                                #16
                                Re: How does this analog ESR meter work?

                                That'll be $20 well spent. Not only will you learn this and that, but this kind of meter actually works when you're hunting for bad caps, because in a piece of equipment that has failed due to bad caps, they're gonna be bad enough to register on such a meter. Just don't expect to distinguish fake caps from genuine ones, or the difference between 0.06 and 0.1 ohm ESR, coz you're not gonna get it.
                                Originally posted by PeteS in CA
                                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                                A working TV? How boring!

                                Comment

                                  #17
                                  Re: How does this analog ESR meter work?

                                  Yeah I don't exactly require exact ESR measurements...but it would be handy to see which are dead or not.

                                  Comment

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