Buying a Basic Multimeter

Discussion in 'General Electronics Chat' started by CircuitSurfer, Apr 6, 2010.

  1. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    Will this multimeter be good enough for general use? Will I be able to measure capaticitance?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Nope... I would buy a fluke.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Don't spend too much on it. It's plenty good for basic usage, but can't check capacitance.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Look at the battery it will be using. Watch batteries suck, and can be hard to get.

    Meters are available from many sources. The Radio Shack meter my folks bought me is still around, even though they are gone. It was overpriced, but it does frequency and capacitance. I like it.
     
  5. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    This multimeter uses a 9V. All I need for now is to measure the voltage and resistance within a reasonable degree of error. Is the error rate on this meter acceptable?
     
  6. someonesdad

    Senior Member

    Jul 7, 2009
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    That appears to be the same Chinese-made DMM model that Harbor Freight used to sell on sale for $4 (I got mine for $5). It's an excellent value for the money, but it doesn't measure capacitance.

    You ask if the "error rate" is acceptable. I ask back, "How long is a piece of rope?" Only you can determine if the accuracy specs are good enough for your needs. For general purpose use, 1/2% DC accuracy and 1 to 2% AC accuracy are typical of low-priced meters. They probably will be fine for your needs.

    If you're going to use a digital multimeter a lot, you'll want to think carefully about your purchase. Personally, I enjoy autoranging tremendously, as I hate having to slow down and turn a range switch like on the old VOMs. When troubleshooting in awkward places, under a car, in the attic, etc., it is nice to have a backlight so you can read the instrument. That meter also appears to not measure below 1 volt AC; for me, that's not good enough, as I often measure lower AC signals. It also doesn't measure AC current, which is another feature I would want.

    For around $70 (last I looked), you can get a Radio Shack meter with a serial interface. You can use it as a general purpose DMM, but it can also be hooked up to a computer to log data. Here's a place with some software support for it.

    For a $5-$10 meter, I don't think you could go wrong in buying it. You'll learn what you like and don't like about it and the next time you buy a DMM, you'll have a much better idea of the things you want.
     
  7. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    I have no need to measure AC so I think this will be a good dmm for me. Thanks for the reply.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    I have a few meters very similar to that one.

    Out of curiousity, I checked one of them against a Fluke Calibrator (a very expensive piece of test equipment used to calibrate other test equipment) and I was quite surprised how accurate and linear it was for the low cost.

    However, I suggest that you don't use it for testing mains voltage, as the internal fuse may not be sufficient to break a high voltage plasma arc. The fuses in the meters I have are rated 125v, which is marginal for household mains in the States; in other countries that use 220vac, an internal fault in a meter could lead to very serious injury or death.

    If you want to monitor mains voltage routinely, purchase a high quality meter from a reputable manufacturer, like Fluke - and always use the specified fuse.

    Cheap fuses + high power may cost you your life.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Fluke..Fluke...Fluke...Fluke...Fluke...Fluke...
     
  10. Markd77

    Senior Member

    Sep 7, 2009
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    Looks exactly like the one I've been using for about 5 years. I'm pretty happy with it.
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Then u never have the pleasure of meeting a fluke....:D
     
  12. someonesdad

    Senior Member

    Jul 7, 2009
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    While R!f@@'s enthusiasm for Fluke is understandable, there are lots of fine meters on the market to choose from, covering a wide price range. There's lots of information on the web, so it shouldn't be hard to find lots of choices. However, the problem with comparing specs is that it's easy to get tied up in knots over the importance of the numbers. You'll find after using a meter daily for a few years that other things you never thought about when looking at the specs are important to you.

    One thing new users/buyers of DMMs might not think about is that often you want to measure current. With the usual meter, that means breaking the circuit and inserting your DMM if you can't find a handy resistor to measure the voltage drop across. In the 1970's I had used an HP 428 clamp-on milliammeter and fell in love with it because you didn't have to break the circuit -- you just clamped the probe onto the wire. Years later I got one on ebay in perfect condition for $50 -- but it is a bit of a pain to lug it around, as it's a vacuum tube instrument. But it still can accurately measure from 1 mA full scale to 10 A full scale -- still an impressive instrument 30+ years later. I think HP continued to manufacture them up to about 1986.

    A few years back I bought a B&K 316, which is a pretty small clamp-on AC/DC current meter (it's spec'd to measure down to 1 mA, but I don't trust it quite that low; I trust it to around 5 to 10 mA). Nevertheless, for $170, it's very portable and measures AC/DC voltage and resistance. I use it in conjunction with my Fluke DMM. The B&K is also the meter I take with us when we go on a trip in our RV, as it's a better troubleshooting tool for the types of problems I might see. The head is 30 mm wide, which means it can get into tight places that normal clamp-on meters can't. It will measure over conductors about 13 mm diameter and smaller. I never need to measure any cables that large, so it's perfect for my needs. It's specified to about 2.5% accuracy on the 10 A scale, which is fine for me (it will also measure up to 100 A AC or DC). The resistance scale goes to 10 kΩ -- this is fine for troubleshooting auto/RV/home AC stuff, but not for electronics stuff, so it won't replace your DMM.

    Some of you folks might not be aware of this instrument and feel it might be a useful addition to your toolkit. I use it more for DC current measurements than I do for AC current measurements. It runs on two AAA batteries.
     
  13. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    Here's an alternative:

    http://www.aeswave.com/products/Product.asp?i=59&tsw=su
     
  14. someonesdad

    Senior Member

    Jul 7, 2009
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    Not a bad choice for the money, but you need to use it with a DMM, which wasn't something I wanted. Also, the resolution would only be 50 mA with a 1 mV resolving DMM -- the B&K resolves to 1 mA.

    F.W. Bell makes (or at least used to make) clamp-on current meters with similar resolutions, but they're much more expensive.

    AEMC sells the same clamp-on ammeter as B&K for $250.
     
  15. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    It has two sensitivity settings; the most sensitive is 10 mA for 1 mV.

    However, like you I'm not sure I'd trust it for really low currents. Since I would be using a clamp on ammeter at the bench, not in the field, I would get out the Tek A6302 clamp on for those low current, high bandwidth currents.

    The fact that it has to be (can be, in other words) used with a DMM, or an oscilloscope is a plus for me. Does the B&K have an output that can drive a scope?
     
  16. someonesdad

    Senior Member

    Jul 7, 2009
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    Ah, then the web page's information was incorrect. I thought that sounded a little insensitive.

    No, it doesn't. When I need that, I use the HP 428 -- but it's all low bandwidth stuff as I don't have a current probe for the scope. The web page you gave said the probe's response is up to 20 kHz, so that's a definite plus.

    I'll keep the B&K because it's small and half the weight of my Fluke, but now I'd love to have the current probe you showed too. Alas, I'd never get the money request past the executive council (aka the wife). :p
     
  17. t06afre

    AAC Fanatic!

    May 11, 2009
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    I do not think a beginner need a Fluke. I would rather invest the money in a good solder iron. You will be able to most of your measurements with a cheaper brand. I have fluke 189 true RMS multimeter (A service man left that, and a Textronic TDS210 scope at my house). But I also have my first digital multimeter. It is a cheap clone of a much more expensive HP multimeter. It is 20 years old but I still use it.
     
  18. Wendy

    Moderator

    Mar 24, 2008
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    To the OP,

    Truth is, brand names tend to be tougher, but other than that it doesn't matter. Get what you can afford. You've probably figured this out from the discussion. I have several meters, sometimes it comes in very handy to be able to make more than one measurement at a time.
     
  19. DustinB

    New Member

    Apr 5, 2010
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    What is your budget? You can get a fluke 87-III at a pawn shop for around $100 or so. As I learn more I'm starting to use a lot more of it's features than a basic meter has. Don't be afraid to buy used good condition stuff, especially fluke. Remember, it's cheaper in the long run to buy something once with features you won't use for a while than it is to buy a cheap meter and then a good one.
     
  20. someonesdad

    Senior Member

    Jul 7, 2009
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    Dang, Bill, that's exactly what I meant to say earlier and forgot (I mentioned the clamp-on current meter, then meant to say that it's sometimes useful to measure the current and voltage at the same time). And, when I'm running an experiment, it's not unusual to have 3, 4, or more meters all reading different things.

    So having a few of those $5-$10 Harbor Freight specials certainly isn't anything to sneer at.
     
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