Buying a Digital Multimeter

[timjturner]

I'm thinking of purchasing a digital multi-meter.... I'd like to make an economic purchase. Any suggestions? I'm also not sure if I need a 46-Range or what? What does this refer to?

Thanks

 

[IRstuff]

You're going to have to do better than this to get a cogent answer. What are the requirements? Why not buy a $10 DMM from Home Depot?

TTFN

 

[jimkirk]

Some things to think about:

Resolution: 3 1/2 digits (counts to 1999 or 3999) are common, 4 1/2 digit will add a bit of a price jump. More than that and you're talking expensive bench type meter. What do you need?

Range is how those counts are used. 199.9 mV , 1.999, 19.99, 199.9 volts full scale. That's four ranges there.

With some meters, you have to select the range, others will autoscale to the correct range.

Ability to measure AC and DC voltage would be eight ranges (four of each). Adding AC & DC current will bring your total to 16 ranges.

Resistance measurement will add another set of ranges to your total.

That's the basics. Then you can get into some more elegant or specialized measurements.

True RMS voltage and current will add a pretty good price jump. Personally, I think it's well worth it.

Other functions you may want: frequency, capacitance, inductance, temperature measurements, transistor checker; all will cost you. Some more than others.

And keep in mind that generally, any meter that can make lots and lots of types of measurements may not be able to do all of them well. A frequency counter will generally have better range, resolution and accuracy than a 3 and a half digit multimeter on its frequency setting.

Some meters (Fluke for one) include measuring seimens. (The inverse of resistance. Useful to measure the quality of insulating materials.) Some meters may have extra high or low range measurements. For example, most hand held meters have resistance ranges that can measure with a resolution down to 0.1 ohm, or up to 20 megaOhms or so (but not at the same time). Do you need to measure much lower than that, or much higher? That will add cost.

Some meters also allow you to log measurements. For example, make a voltage measurement every 10 seconds and store a couple hundred readings that you can recall later. This also costs. Some meters allow a computer interface.

So, think about what you want, need, and can afford. Go to the website of some distributors or manufacturers and see what's available. (DigiKey or Active Electronics as example distributors, Fluke, HP, Tektronix and others make meters.)

 

[zeusfaber]

Also, consider how often you're likely to drop it, and whether what bothers you when you do is the possible (if unlikely) cost of having broken an expensive instrument, or the impact on your job of having to pause to go and buy yet another cheap one.

A.

 

[itsmoked]

As IRstuff mentioned you haven't even stated if you want a bench unit,(no stinking batteries, much higher accuracy, ouchy price), or a handheld,(smaller, cheaper, more uses).

I agree too with jimkirk. Whatever you get get; "True RMS", a continuity tester(beeper), and a diode test function. Those three extras are pretty much a must as you will eventually regret not having each and every one of them.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

On top of all that, "economic" means different things to different people. I need a new "economic" one as well. Mine needs 3 phase input with or without neutral, harmonic analysis, wave form capture, time recording, the ability to save files for download into my PC, serial communications and a few more less expensive frills, plus it needs to be portable but capable of being powered from a PS if the battery dies. "Economic" for me is under $3000.00

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[itsmoked]

Yeah funny how "work" verse "play" allows one to dynamically alter the definition of "economic".

Hey skoggs(MIA) should have some suggestions for you jraef.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Hey jraef,

You are probably scaring the OP - that sounds like a portable power analyser, not a multimeter!

TimjTurner: you need to consider what YOU need from a multimeter. Your requirements might be very different to those of a user from a different industry. My industry needs something tough, simple, reasonably accurate and totally reliable as a general hand-held instrument. Fluke's 20 series is a long-term favourite, even with its limitations (no true RMS ), because it meets those basic requirements so well. I don't need a top-of-the-line handheld day-to-day because when I need a true RMS meter I can borrow something younger than my old 20 series from a colleague, and when I need real precision I have access to bench meters up to 7.5 digits and a lot of other test gear. Without that access to other equipment the Fluke 20 probably wouldn't meet all my needs. If I was buying it today true RMS would be a "must have", but that feature was not very common in handhelds over 15 years ago. It really boils down to the user must understand the limitations of whichever instrument he is using in order to get the best out of it, and when he needs to use a different instrument. There are no meters which are all things to all men.

An hour spent poking around on the Fluke website

http://www.fluke.com/

looking at the different types of meter and their limitations and capabilities will help you work out which functions are "must have" and which are either "nice to have" or "don't cares". Once you have identifed those factors you will be in a much better position to buy a meter. Fluke's technical notes are obviously biased toward their products, but there is a huge amount of general information too. I've no particular allegiance to Fluke other than as a long time user of their products.

One other thought is that good quality meters frequently appear on eBay. You could save a fair bit of money on a meter which would be expensive through regular channels.

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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

I'd buy anything BUT a Fluke.. I just don't like them.. I'd rather have 3 identical meters with all the usual than one Fluke.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Hi Keith,

I like their multimeters. Their scopemeters are a pale shadow of the Tektronix equivalents. Some people love 'em. Just depends on personal preference! Whose multimeters do you like?

 

[Skogsgurra]

I used to buy cheap DMMs. But no more. I used to buy Fluke - always the top models. But now I am using a MetraHit 29S. Why? Because I love a competent instrument. And doing what I do (that means not knowing what I will be looking at next week) I love that Swiss Army Knife they packed into the 29S. It has three voltage measuring methods, current, watts, frequency (five digits). It looks for maximum/minimum for hours, it logs and it measures temperature as well as capacitance and resistance. And there's more that I haven't found out yet. Yes, love it.

There is a lot said about how necessary TRMS is. Yes, mostly, but not always. Consider measuring current out of a battery charger. What would you use? Mean or TRMS? Why?



Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Wow Skogs. A data logging cable and software that costs half what the meter costs.. Seems steep. What can the software do for you?

Can it do watts verse VA?

Also, I wanted to see the unit well, but I can't find a single picture that I can actually read a button on..

Scotty; mostly higher end mutts $100-200 variety. When I get to the office today I'll look.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Skogsgurra]

I don't log to a PC. But very handy when you want to take a pee. No. I don't have any extras with that meter. But it surely does W, VA and var. For more channels, I use a recorder or a DSO and for power quality it is a Dranetz 4300. But this is about multimeters, so I don't mention them.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

OK Keith,

Here it is. Picture made for you! Fresh from camera.

I didn't bother with test leads. It is so sensitive that you can just move your fingers across the connectors to get some millivolts to record. The meter is in max/min mode and shows actual voltage in the main display while it shows minimum and maximum voltage so far in the to extra displays. That works also in W mode where you have watts in the main and V plus A in the extra displays. Or AV voltage, you can then have V in main and frequency in one of the extra displays. Forgot what you get in the third display. See why I love it? Have had it for five years or more.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

One of the guys at work has one - I borrow it for things which my old Fluke 25 isn't suitable. It is a nice meter. I think the manufacturer is Gossen Metrawatt.

We poked fun at the red shields over the sockets not used for the selected range, primarily because the owner of that meter is the youngest in our group and we are opportunists looking for an excuse to tease him. Weeks later someone had a bit of a fright when he measured voltage on a high energy 415V board using the current range. No more laughter about little red shields. Incidentally, that near-miss would have been much more serious if he had not been using fused probes. They are a pain for many tasks because they are large and clumsy. On high energy circuits they might save you from serious injury.


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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

Yikes Scotty! It's sooo easy to make a serious mistake with a DMM around higher voltages. I probably blew 25 fuses in my earlier years by not paying attention to the fact that I last read amps... Haven't done it in many years now as I finally trained myself out of it.

Hey thanks Gunnar! I see. It's auto ranging.

Q1) How fast does it settle on the correct range?

Q2) On the minimum reading is it smart enough to, sort of, figure out what the minimum is after hookup or do you hit the 'clear button' after hookup?

Q3) What's that 4.2V hole on the bottom right?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

http://gossenmetrawatt.com/resources/tt/hit28-29s/ba_gb.pdf

 

[Skogsgurra]

Keith,

A1 I have no exact number. Half a second or so. But you can press the MAN button to have a fixed range. I usually do.

A2 No. It ain't that smart. You have to press CLEAR to start a new min/max measurement.

A3 It is for the mains adapter. Power measurements do consume batteries (probably a lot more activity to calculate everything) so a kWh measurement over several days needs external power supply.

Scotty,

I did use those clumsy fused probes earlier. Those with 10 A HRC fuses in them. Never felt comfortable with them. I now use another type, much more like normal test pins. They have 500 mA fuses in them and a current-limiting resistor that avoids high currents. They are marked 600 V 50 kA and are also much lower cost than those 10 A fused ones. There is one little problem, though; do not forget the internal resistance in the test pins if you are measuring resistance. I just remove the pins and use 4 mm banana plug test leads when I do resistance measurements.

And, thanks for that manual link. I have lost my original manual. This new one looks a lot easier to follow. Wow! It is like having a new instrument to explore!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Thanks for the info Gunnar.. Something new for my 'want list'!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[LionelHutz]

We work with 600VAC systems and VFD's here so we buy CAT III @ 1000V / CAT IV @ 600V rated meters. This helps ensure the meter won't blow up in my hand if I do something stupid with it. Last meters purchased were Fluke 1587 meters.

Fluke does/did have some type of lifetime warranty plan. I killed a Fluke 87 that was around here for years and they fixed it for free. I was quite proud of the fact - it's almost impossible to kill those things. It wasn't very dead though - it just needed some protection components replaced. Typical wrong range or wrong test lead connections don't hurt them. Attempting to measure voltage in a current range requires a new fuse.

I would like these as basics;
Autoranging
AC/DC volts to 1000V
AC/DC Current to 10A
Resistance
Diode
Frequency
Continuity
True RMS
Min/Max capture
CAT III 1000V, CAT IV 600V
Temperature - it it's a good probe

For me, that covers the basics and anything else is a bonus. For you ????.