Multimeter question

Discussion in 'General Electronics Chat' started by enduro250z, Aug 30, 2010.

  1. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    I want to buy a decent multimeter and have narrowed my selection down to the Fluke 87 or Fluke 88

    The main difference is that the Fluke 87 is a true RMS meter for AC and the Fluke 88 is an automotive specific meter that has RPM and Dwell measuring capability but its also one of the only Fluke meters that doesnt have true RMS readings, but other than that the specs are very similar

    as seen here

    http://www.test-equipment-shop.com.au/catalog/Fluke_Multimeters-61-2.html

    i cant really decide if i really need to have a true RMS meter. How important is it to have a true RMS meter? Is that what everyone uses these days? Is it the only way to today if you want seriously accurate measurements?

    Although i will mainly be using it for automotive use aswell as testing circuits in electronic components and measuring resistors and capacitors etc, the RPM and dwell isnt all that important to me and i doubt i would use it. The RPM i will probably cover that with a timing ligth i want to get. I wont be using the meter on 240v mains power.

    Please dont suggest a cheap $29.95 meter because i have a box full of them that dont work and they dont last and are poorly made in one way or another. The people i have spoken to so far have said the Fluke is the only way to go if i want a really good meter thats well built and going to last.

    Thankyou for your input
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    #1: Unless you own some really old classic cars with a points distributor the dwell function is of no use.

    Having an AC amps scale is.

    I have a Fluke 27 Digital/Analog Multimeter that came with the factory case, manuals and a 80k-6 probe, got it off eBay for about $65 + $11 shipping in virtually mint condition.

    Large readout, large switch and ruggged as heck - probably because it's the FM model made for the military (thus black instead of the traditional yellow case)

    I'd highly recommend looking up the specs on these, it's quite a bit of meter for the money especially if you can catch one nobody's in a bidding war on. It's also easier to get the FM model at a decent price, since it isn''t yellow some people shy from them thus there's less people bidding on them.

    Out of all my meters I've never had a handheld that would measure AC Amps without being the clamp on type. This has a 0 - 10A AC range that's good across a really wide frequency range. It has really come in handy several times more often than you'd think.
     
  3. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    Yeah i have found some good new ones on ebay. I can get a Fluke 87 for under $300 USD but buying it brand new in Austrakia is around $700-$800 AUD!!!!! and the Fluke 88 is just under $1000 AUD! Much cheaper for me to get one off ebay USA.


    Yeah dwell wont be much use to me

    both the Fluke 87 and 88 have AC amps up to 10a. I was also going to get a addional clamp on high current clamp to measure higher than 10 amps which i want for measuring stator outputs.
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    THey make a lot of accesories that are interchangeable among their meter lines.
     
  5. someonesdad

    Senior Member

    Jul 7, 2009
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    I'd agree with marshallf3 about the convenience of a 10 A AC/DC measurement being handy. However, with lots of use, you may find that you'll blow the fuses protecting the current measuring feature -- and these fuses aren't cheap to replace, being $5-$10 each. Thus, if you measure current reasonably often, you'll want a clamp-on meter anyway -- I eventually bought one that measures from 1 mA to 100 A for both AC and DC current and have been happy with it. I consider the mA and μA scales critical, as I find I make those measurements more commonly than 10 A measurements. When I'm at my bench, I use my HP 3435 for these measurements because it has a simple-to-replace AGC fuse protecting it. Again, the Fluke fuses (there are two of them) are expensive to replace.

    About 20 years ago I bought a Fluke 83 as my DMM to replace an older Fluke DMM that lasted less than 10 years. The Fluke 87 was available, but I didn't feel the extra cost for the RMS feature was worth it. Now I do and regret than I didn't spend the extra money for it. So I'd recommend getting the Fluke 87.

    Note that many DMMs don't really measure RMS values -- they measure the AC-coupled RMS value, just like an HP 3400. If you want the true RMS of a waveform, you need to measure the AC-coupled RMS value and the DC value, then add them in quadrature. I've always been a bit annoyed at the marketing people for lying to us about this and calling it "true RMS". If you want a real RMS measurement, look for a meter that measures AC+DC RMS.
     
  6. Jaguarjoe

    Active Member

    Apr 7, 2010
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    I got a Fluke 85 about 17 years ago. It is identical to the 87 except it does not have a back lit display. I never was a fan of playing with electricity in the dark so this didn't matter to me.
    Like someonesdad sez, fuses are easy to pop and expensive.
    The meter has performed flawlessly so far. I have a DC current clamp on attachment for it so I can measure car battery discharge current and alternator output current.
    Like Marshalf3 sez, dwell is useless nowadays. The 85 or 87 measure frequency which is just as good as RPM.
     
  7. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    Well ive almost made my mind up on the 87 instead of the 88 and the 87 is cheaper too. With the 88 your paying a lot more for dwell/RPM or the fact that its called an 'automotive' meter and they whack a few xtra $100 on the price, because other than that its pretty much got the same specs as the 87. Now i just need to think what 'someonesdad' said about true RMS. The 87 has it only for AC, now i need to look at what has it for AC and DC. Thanks for the advice so far, it has helped me a lot.

    It looks like Fluke only have the 287 and 289 with AC/DC true RMS but i reckon they might be out of my price range (need to check) so i might just end up going with the 87.

    Im just wondering if the logging feature of the 287/289 would get in my way or not? Doubt i would need to use it.

    Also whats your thoughts on getting new meters calibrated? I spoke to an ebay seller selling a fluke and they said in their ad that they have got ISO ...blah blah blah certicfication or what ever to get meters properly calibrated in a lab for an aditional fee and they said its worthwhile to even get brand new ones calibrated. Sellers name is accurateelectronix
     
    Last edited: Aug 30, 2010
  8. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I rarely need perfect accuracy, if it measures almost exactly on new 1% resistors and is almost identical to other meters when measuring voltages. currents etc it's good enough for me.

    I had no clue the fuses were that expensive, luckily I've blown enough in cheaper meters over the years that I'm pretty darn careful about not overloading the input. I've got a couple of clamp-ons for that kind of work.
     
  9. tom66

    Senior Member

    May 9, 2009
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    I have a cheap meter and it's all I've ever needed. The fuses are about 10p each (both the 500mA and 10A ones.) Does this mean they won't blow properly? No, I've blown both the 500mA and 10A fuses with a little over the limit. Inconvenient, but hopefully safe. Worst case, I ruin a £22 meter.

    However, since you're buying a Fluke, EEVBlog always has something good to help choose between meters. Dave Jones is quite a fan of Fluke.

    Make sure you're comparing apples to oranges. For example, input protection? What is the 87 rated for, compared to the 88? 1kV should be more than enough (even 600V is usually fine.) What about ADC counts. Doesn't the 87 have a special mode where it goes into a higher resolution?
     
  10. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    You lost me there. I was just comparing the specs at bottom of page here

    http://www.test-equipment-shop.com.au/catalog/Fluke_Multimeters-61-2.html

    I will try and find 'EEVBlog'
     
  11. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    For my needs, the vast majority of the time an AC-coupled RMS measurement is fine. If I need AC+DC, I'll haul my bench meter or my digital scope to where I'm making the measurement.

    A year or so ago I took a look at Fluke's latest DMM offerings to see what purchase decision I would make if I had a few hundred bucks handy. I decided against the 287/289 because a) they were bigger than the 87 and b) I don't need the datalogging. I have an el cheapo Radio Shack DMM with an RS-232 interface and a laptop that can substitute reasonably for that task (but it won't have the data rate that the Flukes would have). I definitely settled on the 87.

    The last time I measured the dwell on a car was in the 70's with a Heathkit Dwell/tachometer kit I built. That's probably a feature you can do without.

    I would recommend against paying for an instrument calibration -- it's almost certainly a simple profit center for the seller. Every few years I check my Fluke 83 against my old HP 3456 system voltmeter and my Fluke 893A differential voltmeter. The differences are completely ignorable -- all three of these are stupendous instruments. Even the $5 Harbor Freight DMMs can do a reasonable job with respect to accuracy.

    When you think about it, so much of what you use a DMM for is as a differencing tool. For example, if you're troubleshooting something on a car, you'll measure the battery voltage, then subsequent measurements are with respect to that battery voltage. Even if the DC accuracy was off by half a volt, you'd probably still make the correct troubleshooting conclusions.

    A time where accuracy matters is when you're converting an electrical signal to another physical unit via an electrical transducer. Then you do want accuracy to avoid systematic errors.
     
  12. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    Thanks for the comments. Im getting so much help from this. I found EEVblog on you tube and i learnt a lot off him and watched his 50min video and took notes. The Fluke 87V seems like the one to get for sure and it meets pretty much all the requirements set out in the video.
    I usually dont like to just get what everyone else gets, but i guess all the people who have bought one of these meters has read the specs and also realised that there is a reason why they are one of the most popular meters.

    One thing i would like to know is, when you take the cover off to replace the fuses and battery, are the screws direct into plastic or metal inserts on the Fluke 87V ?

    The ebay seller offering calibration to a new meter said its an extra $39 US (normally $79). I reckon if i got one from them i would pass on that. EEVblog never suggested getting your new meter calibrated. I guess if i wanted to, after a while i could sent to Fluke and have them check it over.

    I dont think i need data logging and i think just true RMS on the AC section of the 87 will be enough. Data logging meter may chew through more batteries.

    My only other delema is, im thinking i should have 2 meters now so i can measure volts and amps at the same time, i would use that for sure and i think 2 meters would be good for comparing to each other. If i got the 87 that would be my really good one, but im wondering for a second meter i would like to get one that doesnt cost as much but is still very good. Not sure if i should go for another good brand or just get a lower spec/lower dollar Fluke to suppliment the 87V?.

    Initially i was looking at a Extech as they seemed to look good and had a high price and i was almost hooked on getting one because they could measure up to 20A but the i was put off by the fact the manufacturing is offshore and not in USA and i also realised i could get a current clamp to measure higher than 10A on the Fluke 87.
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
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    For now I woudn't start buying a lot of expensive equipment you'll rarely have the need for. Watch the ads at http://www.harborfreight.com and be sure to sign up for their flyers. They sell a nice little DMM that varies in price from $6.99 down to $1.99 depending on whatever sale(s) they have going on at the time. The price in the flyers may be cheaper than what's shown on the website or sometimes it's the other way around. If you ever see something on sale on the website it pays to print that page and take it with you, the local stores aren't in touch with what's being offered for sale online.

    Back to the subject, I own several of these little $1.99 meters and have found them to be pretty darn accurate except when you're trying to measure low values on the very lowest resistance range, but that's common with most any DMM.
     
  14. Jaguarjoe

    Active Member

    Apr 7, 2010
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    Here are 3 Harbor Freight meters on sale for $2, $4, or $18:

    http://www.harborfreight.com/catalogsearch/result/?q=multimeter

    I have 1 $2 unit and 1 $4 unit. I don't have them in my hand right now but I believe the $4 unit also tests transistors. That $18 meter is the next best thing to a Fluke at 1/15 the cost.
     
  15. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Last edited: Aug 31, 2010
  16. enduro250z

    Thread Starter Member

    Jul 6, 2010
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    As i am a motorcycle mechanic i need something better than a $2 meter! Ive been through about 10 cheap meters. They just dont cut it. I will be getting a decent one which i should have done a long time ago. I think im pretty much settled on the Fluke 87V though.


     
  17. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I don't think any of us are suggesting the $2 meter as your mainstay, it's just that at that price you can afford to keep some extras tossed around for simple things like checking for voltage presence or testing fuses.

    I think I've got about a half dozen of them strewn about for this very reason and if someone "borrows" one I probably wouldn't even notice. I keep my Flukes locked up at work.
     
  18. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
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    What, on a motorcycle or car, requires a Fluke 87? There are prolly 100's of DVM's much less expensive than the Fluke that will serve you just as well.
     
  19. marshallf3

    Well-Known Member

    Jul 26, 2010
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    True, but you can drop a Fluke 10' onto the concrete and it won't hurt it.
     
  20. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    You can pull it out of a bag of tools it's bounced around in for years and will still work and will maintain it's calibration to better than spec the whole time. Good tools of any kind are worth the investment.
     
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