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Decent DMM for around $250?

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    #21
    Re: Decent DMM for around $250?

    Originally posted by fzabkar View Post
    I have a Fluke PM97 scopemeter which I bought new for AU$2750. It's been a POS since day 1.

    Nowadays I stick with cheap DMMs and test their accuracy with a cheap precision reference (5.000V +/- 5mV).
    I need to get a cheap precision reference... and continue using my cheap 2000/4000 count meters...

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      #22
      Re: Decent DMM for around $250?

      I built something like this:

      http://archive.siliconchip.com.au/cm...3/article.html

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        #23
        Re: Decent DMM for around $250?

        I just need to get a couple of those laser trimmed chips... augh...

        I actually found some reference voltage chips but they are not exactly as accurate as what you can get, alas it may be good enough. Forgot what they were off the top of my head, but the thing I was a bit worried about is that these are SMT chips and soldering them may affect their trim...

        I guess DIP may be better in this respect as long as you don't draw too much current...

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          #24
          Re: Decent DMM for around $250?

          Maxim provides free samples ...

          Here is another chip:

          https://cdn.badcaps-static.com/pdfs/...7d2214fb0f.pdf

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            #25
            Re: Decent DMM for around $250?

            Ah REF198GS is what I have... Unfortunately it looks like it's 4.096V +/- 10mV so it's pretty inaccurate, but might be good enough, though still pretty horrible though.

            Now the other problem is that at 4.096V, I'd need to locate 0.1% resistors or something to make a voltage divider to get it within the 4-digit 1999 count... Or I might go ahead and try to "bin" a few resistors that I already have that match each other, and use those to make a 3:1 voltage divider...

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              #26
              Re: Decent DMM for around $250?

              you are probably wasting your time once you allow for the volt-drop in the cables and connectors.

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                #27
                Re: Decent DMM for around $250?

                Originally posted by fzabkar View Post
                I have a Fluke PM97 scopemeter which I bought new for AU$2750. It's been a POS since day 1.

                Nowadays I stick with cheap DMMs and test their accuracy with a cheap precision reference (5.000V +/- 5mV).
                The later DMM series have better accuracy than 5 mV so fur such testing it is of no use. I guess +-0.5 mV would do.
                Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

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                  #28
                  Re: Decent DMM for around $250?

                  Actually the MAX6350 has an initial accuracy of ±0.02%, so that's 5.000V +/- 0.001V, not 5mV. Sorry for my error.

                  https://cdn.badcaps-static.com/pdfs/...9ffece5239.pdf

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                    #29
                    Re: Decent DMM for around $250?

                    +-1 mV, still the same level than most these better multimeters measure. Should be at least a digit more precie than the multimeter itself I'd say.

                    In this case it may be used for the UT61B as it has 4V and than 40V range, but some other meters have even 6V range so they could measure 5.000 V.
                    Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                    Exclusive caps, meters and more!
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                      #30
                      Re: Decent DMM for around $250?

                      Why buy a Fluke then?

                      BTW, my tester has the 5.000V, 4.096V, and 2.500V references.
                      Last edited by fzabkar; 11-25-2015, 02:50 PM.

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                        #31
                        Re: Decent DMM for around $250?

                        Originally posted by stj View Post
                        you are probably wasting your time once you allow for the volt-drop in the cables and connectors.
                        The 10M ohm input impedance on the "better" meters and this isn't that big a deal - the resistance of the cables and connectors are several orders of magnitude off from the resolution of the display (except in amperes mode). But it would be nice to at least know if the pots on the meter haven't been disturbed.

                        I did notice my Tek (probably at least 35 years old) and Fluke (probably 25 years old), after all the years they've been out after leaving the factory, still match each other except the last digit, typically by one count (Tek is 1999 count, Fluke is 3199 count). All my other meters are all over the place.

                        I think my LED Viz meter has the most error from the Tek/Fluke comparison (surprisingly NOT a HFT meter) alas I have no idea how to calibrate it, too many pots on the board...

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                          #32
                          Re: Decent DMM for around $250?

                          Originally posted by eccerr0r View Post
                          I think my LED Viz meter has the most error from the Tek/Fluke comparison (surprisingly NOT a HFT meter) alas I have no idea how to calibrate it, too many pots on the board...
                          Heat up the area close to the trim pot with a solder iron tip (but not touching the trim pot) or use freeze spray on the pot as per this video.

                          https://www.youtube.com/watch?v=B9E4XpUfoc8

                          Adjusting it back within specs may only be a temporarily fix if the multimeter drifts over time.
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                            #33
                            Re: Decent DMM for around $250?

                            There are around 5-10 trimpots IIRC in the Viz... The recent LCD DMM's I've only seen 1 or 2 at the most...

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