Meter Question

Discussion in 'General Electronics Chat' started by Dr.killjoy, May 29, 2013.

  1. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    I am a noob when it comes to electronics but i have been in the game for some time... But right now i am using a fluke 77series II multimeter which i use for everything but I keep getting told that i should pick up a rms meter and with better accuracy and before i pull the trigger what do you guys think????????






    Thanks ahead of time
    JAy
     
  2. crutschow

    Expert

    Mar 14, 2008
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    If the meter measures with the DC accuracy you need and you don't particularly require the RMS value of AC waveforms other than sine-waves (such as square-waves), then I wouldn't buy another meter. That Fluke is a very good meter.

    What do you use the meter for?
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    If you need the accuracy (true RMS) then you need it.. If you don't you don't..

    I've got a Fluke 89 IV (true RMS) its a great meter.. I needed the true RMS feature once (8 years ago) and have never needed it again.
     
  4. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    I really only play with DC mostly and is the accuracy worth it ?? I was looking at picking up a Uni-t61E for $55 bucks shipped to my door ...
     
  5. #12

    Expert

    Nov 30, 2010
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    In nearly 50 years of designing and repairing, I've been everywhere from nanoamp errors in opamp circuits to multi-killowatt furnaces, and I've never had a True RMS meter. If you can't name why you would need one, you don't need one.

    On the other hand, if the price difference is only 10 or 20 bucks, go for it. A tool you don't need is better than a tool you don't have when you need it.

    Edit: There is no need for a True RMS meter for DC.
     
  6. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    LOL Thanks for the info but I already have the fluke 77 series II at home but I can't come up with a reason for my self and my wife why I need one beside the fact I just want one with a little bit better accuracy..
     
  7. Georacer

    Moderator

    Nov 25, 2009
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    An important factor is whether the instrument is going to be used to measure mains voltage. If it is, then you probably want a CAT III input protection rating, not a cheep pocket one.
     
  8. tindel

    Active Member

    Sep 16, 2012
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    If you already have a meter for DC then I wouldn't bother... I'd rather have a good scope that shows me the waveform than an RMS meter. If I didn't already have a meter I'd probably spring the few extra bucks for the True RMS though.

    It depends on the job though - I'm in the lab and need high quality tools... if I was working in the field as an electrician then an oscilloscope isn't very portable and wouldn't be conductive to getting the job done quickly.

    Fluke does make some portable oscilloscopes that are great for electricians too, but I'd imagine they are a backup tool in most electricians tool boxes.
     
  9. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    True RMS meters are over rated because their range of accuracy is extremely restricted because of how they calculate the TRMS. For most people it's a waste of money. The only TRMS meters that are really accurate use thermal measurement and they cost MANY thousands of dollars.
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    KillJoy,

    You are worrying too much about the tools. I wouldn't know (and in many situations I wouldn't care) if my meter had a 5% error. It has not been calibrated since it was new. I have an old Kiethly voltage meter plugged into my power supply that is surely off by 3 or 4% vs. my two Fluke meters (an early version of 87 and and old, old 8025a) - I don't know which is wrong.

    In digital electronics, it is either on or off, so why worry?

    In audio, it either sounds good or it doesn't . Trying to push the gain to get 5% more before you start clipping is rarely worth it because other distortion issues start encroaching anyhow.

    In motor speed controls and sensors, you have feedback systems that are self-correcting.

    I cannot think of a case recently where I was saying, "gee, that voltage should be 5.0, not 5.25 volts.

    You might want accuracy if adjusting temperature controls but, surprisingly, that is all that immediately comes to mind for the home hobbyist.

    Spend money on parts and projects or take your wife out for dinner.
     
  11. Georacer

    Moderator

    Nov 25, 2009
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    Well, 5.25V instead of 5V in an analog biasing circuitry could degrade the results, but 5% DC error is unheard of in any modern meter, as far as I have experienced.
    Generally, if you need a feature, you know it beforehand.
     
  12. vk6zgo

    Active Member

    Jul 21, 2012
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    Keep the 77---you'll be disappointed in the UNI-T,if it's anything like the ones I've used.
     
  13. crutschow

    Expert

    Mar 14, 2008
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    There are few places you really need high accuracy in electronics. One of the few is if you have a high accuracy A/D or D/A converter with many bits and you want to tweak the reference to give a precise conversion value. But few hobbyists require that. And to really insure such high meter accuracy, it needs to be professionally calibrated every year or two, which is not cheap.
     
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