Digital Multimeter Revisited

In my last post I claimed that the digital multimeter I installed in place of the old analog meter was more accurate.  Professional engineer Bob Salnick, author of Windborne In Puget Sound, very gently challenged my claim, asking how I knew that the digital meter was more accurate than the analog meter.

Truth is, I don’t know.  My claim is baseless.  I just assumed (and hoped!) that it was true.  As I explored methods of verifying the accuracy of a multimeter this morning, I learned a few things:  1) I only understood about one-third of what I read about testing a multimeter for accuracy.  I think the concepts are fairly simple, but the details engage a vocabulary and set of technical skills that I don’t possess;  2) Cheap digital multimeters have no corner on the accuracy market.  My cursory reading of digital multimeter reviews revealed inconsistency in most lower priced models;  3)  Higher-dollar “marine” meters may well be quality instruments, but it takes a fair amount of reading manuals, consumer reviews, and technical reviews to be sure that what you are buying (or have) gives accurate information;  4)  A quality multimeter is expensive – as much or more so than a “marine” instrument.

So there you have it.  Apologies to all for spreading spurious information, and my thanks to Bob Salnick for his commitment to fact and his gracious spirit.

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4 comments
  1. Oh dear – I didn’t mean to cause this…

    And your comment that tapping on the analog meter caused its reading to change indicates that it has a sticky movement, thus very likely causing inaccurate readings – a digital meter will definitely not be subject to such mechanical foibles.

    bob

    • Bob, I appreciate the sanity check. No worries on any account. If I can’t tolerate a question, then I’ve got no business writing about stuff. Thanks again!

  2. It’s hard to gauge the accuracy of a multimeter without spending too much on additional equipment, so it’s always a matter of trust and intuition when trusting the reading. Learned a few things about multimeter accuracy from your post, thanks.

    • David, I’ve since purchased an identical (cheap) multimeter and compared the readings. They are not the same, varying as much as .015 volts. I guess I should be happy that I can get an estimate of relative battery voltage. As I accumulate more experience with the meter(s) I can get a feel for what the state of charge is in my battery bank. If I want a more accurate accounting of battery state, I’ll have to invest in something that reliably measures amp-hour usage. Here’s a link to a battery monitor reviewed by a marine professional I trust. http://www.pbase.com/mainecruising/need_a_monitor.

      Having looked at your profile, I doubt there was much you could learn from me about multimeter accuracy, but thanks for the nice comment anyway!

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