Looking for a good DMM

[KevinL]

Looking to step up to equipment that's a little better than the $9.95 DMMs you find at most places. The most important things I need are DC voltage, DC amps up to 10A (since I work with very high current mods), continuity tester with beeper and resistance check.

My existing DMM is messing with my mind and it's not pleasant.. /ubbthreads/images/graemlins/frown.gif

What do you guys think of the Meterman 34XR? I was thinking it's either that or one of the smaller Flukes, perhaps a closeout on the 83 Series III.

In particular I need accurate readings on the 10A scale.

 

[Pydpiper]

You can never go wrong with a Fluke, if that is your budget. The Meterman seems pretty well equipped, I like the idea of having the option to measure temps, that could be benificial in so many ways.
Just find one you are comfortable with and don't mind staring at for minutes at a time.

 

[andrewwynn]

I've been using flukes since the 70s and for serious work i wouldn't go any other route. the latest high-end models seem to have no problem with measuring the current of switching power supplies.. you can get a kick butt meter like the 87iii for under $100 on a good eBay buy.

I use an 87 and an 87iii.. i'm thinking of selling the 87 and getting an 87V.

They will both measure average over time which is awesome for pulsing devices like a cellphone or home phone that 'pulse' the power when in standby and would be impossible to measure the current drain other wise (i.e.. they have an 80mA pulse, but only every second or so.. the meter will measure the actual true RMS average).

You'll be happy you spent the extra..

I bought my 87 for $325 and my 87III for $250 (both new).. the 250 deal was a 'going out of biz' sale.. but i've seen both for $100 used on eBay and it'd be worth it.

-awr

 

[MikeLip]

I have a couple of Protecs that I like a lot - I also have Flukes (a 111) and some pretty expensive stuff like an HP974A and a B&K 5390.

This is a great, inexpensive bench meter, with a nice RS232 interface and datalogging software;

http://www.circuitspecialists.com/prod.itml/icOid/4668

Also a very nice handheld, and with .025% DC accuracy is this guy;

http://elexp.com/tst_m608.htm

I have both these meters, and the bench meter is pretty decent, but the 608 is an excellent value. They both are, really.

If you are looking for something that will handle peaky readings, like pulsed waveforms with short duty cycles, you need a meter than has true RMS, and which measures DC+AC signals. Also of interest is the crest factor the meter can handle. Most meters can't accurately read signals with a crest factor of over about 3, and that includes about all the Fluke handhelds - and of course the meters I pointed out, even my big buck HP. The only portable I've found that works well on high crest factor signals is the B&K Precision 5390, which goes up to a crest factor of about 7. But it costs $$$ - I've found it worth it.

I also have a Meterman 35XR - nice meter for general use, and in truth 99% of people would be fine with it. I love the non-contact voltage sensor on it. I used it to find a dead spot in a Christmas tree light string this winter /ubbthreads/images/graemlins/grin.gif

I would give Extech a miss - I have one of their scopemeters, and I'm pretty disappointed with it. Very slow response, barely within it's accuracy spec, and it's battery hog. Everything else seems to run forever on a 9V battery - the Extech sucks up 6 AAs in a few hours. Maybe stuff other than the scopemeter would be better, but if I had to do it over and I wanted a portable scope, I'd have bought a Fluke.

Anyway, that's my take. I've used a lot of meters over the years, and found that you don't have to spend a fortune to get a good one. Brands like Protec, Fluke and B&K are a good way to stay out of trouble.

Mike

 

[KevinL]

Cool.. I got some numbers today, $99 for the Meterman 34XR, $250 for the Fluke 87 Series V.

I would love to own the Fluke, their reputation precedes them and their network test gear is *THE* solution to have. Unfortunately my participation in one too many group buys have eaten the budget /ubbthreads/images/graemlins/grin.gif I am not that serious a user, I'm more a modder who'd like a better DMM since I use mine every day to check battery voltages, amongst many other things.

Temperature would also be awesome (something the lower end Fluke 112 - which I was eyeing too - doesn't do). I prefer my Luxeons medium rare, not overdone. /ubbthreads/images/graemlins/grin.gif

 

[MikeLip]

Now HERE is a deal!

http://www.lashen.com/vendors/protek/default.asp

Check the 608 - I bought mine from Lashen and paid $170 for it. As always, I should have waited. The Protec 608 is a really great value, and it does temperature and logs data to a PC via RS232. .05%, 4 1/2 digits (50,000 counts). Super meter at a great price.

Mike

 

[jtheodas]

I don't know much about DMMs and just started learning about them. It sure is hard to figure out which one to get.
This seems like a good one at a good price to me.

What do you guys think?
Protek D980.
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=D980

 

[MikeLip]

Not too bad. Check this stuff out too. Electronics Express is a good place to find inexpensive test equipment.

http://elexp.com/tst-mult.htm

Look at the Tripletts. There is one there that looks good - the 9005.

Mike

 

[Crux]

[ QUOTE ]
KevinL said:
...The most important things I need are DC voltage, DC amps up to 10A (since I work with very high current mods),...

[/ QUOTE ]

For measuring high currents get a low Ohm resistor, 0.1 Ohm to 0.01 Ohm rated at 5 or 10 watts and measure the voltage drop accross it, then calculate: V/R=I. The actual resistance is not critical as long as it is known. This method also removes excess test lead resistance from the measurement. A 0.1 Ohm 10W will measure 5A safely. Yes, it will get hot.

Example: If you measure the current of a 3C direct drive MagMod by connecting ammeter leads in place of the tail cap, the current flow will be lower due to the extra lead resistance. Measuring voltage drop across a 0.01 Ohm resistor placed right at the tail will result in a more accurate reading.

Additionally, if (or when) the current exceeds expectations /ubbthreads/images/graemlins/eek.gif, it is a lot less frustrating smoking a resitor than trying to find a new exotic fuse for your meter (and maybe test leads too...). /ubbthreads/images/graemlins/rant.gif ...not that this has ever happened to me... /ubbthreads/images/graemlins/crazy.gif

 

[udaman]

[ QUOTE ]
Crux said:
[ QUOTE ]
KevinL said:
...The most important things I need are DC voltage, DC amps up to 10A (since I work with very high current mods),...

[/ QUOTE ]

For measuring high currents get a low Ohm resistor, 0.1 Ohm to 0.01 Ohm rated at 5 or 10 watts and measure the voltage drop accross it, then calculate: V/R=I. The actual resistance is not critical as long as it is known. This method also removes excess test lead resistance from the measurement. A 0.1 Ohm 10W will measure 5A safely. Yes, it will get hot.

Example: If you measure the current of a 3C direct drive MagMod by connecting ammeter leads in place of the tail cap, the current flow will be lower due to the extra lead resistance. Measuring voltage drop across a 0.01 Ohm resistor placed right at the tail will result in a more accurate reading.



[/ QUOTE ]

1. Crux, can you provide a more detailed explanation for the logic here of why the resistor is of significantly less resistance than test leads? How much resistance as a percentage of the total, compared to a resistor, which you say will get HOT. Does not the fact that it gets hot, imply that this method will also induce resistance?

And if so, then what is this percentage of total?

2. Tail cap? Umm, while convienent, is this the most accurate point we can test from, or are there better points which would give higher accuracy?

On a MagMod, there are numerous/various points of resistance in any given circuit; so test leads are only one point in the long chain if you measure from the tail cap area.

 

[udaman]

[ QUOTE ]
KevinL said:
Looking to step up to equipment that's a little better than the $9.95 DMMs you find at most places. The most important things I need are DC voltage, DC amps up to 10A (since I work with very high current mods), continuity tester with beeper and resistance check.

My existing DMM is messing with my mind and it's not pleasant.. /ubbthreads/images/graemlins/frown.gif

What do you guys think of the Meterman 34XR? I was thinking it's either that or one of the smaller Flukes, perhaps a closeout on the 83 Series III.

In particular I need accurate readings on the 10A scale.

[/ QUOTE ]

I don't know about the Meterman's, but I believe they are also made in China like the Extech, while Fluke are USA, correct?

Extech EX430 does all of the things the Meterman does, but costs $79---Ture RMS, which is only of signifance in measuring AC current, not DC. It however is one of the few that will measure 20a loads---I think some BK's do too, but you have to check. (many inexpensive models specify for only 30 seconds, others do not). Just how accurately do you need to measure 10a?

Actually, I'm thinking I don't need True RMS accuracy for AC, so the manually ranging EX410 is the least expensive model that measures 20a at $39. Manual ranging EX411 is True RMS at $59.

For a bit more money(too much for me, and I likewise need to upgrade my various inexpensive $30 small DMM's that go up to 10A) MT330 $129 is True RMS and has PC connection software(option), non-RMS MT310 is $79. Measuring differential voltage drops with a resistor as Crux states, maybe more accurate, but kind of a PITA, when you could easily use a 20a DMM. Extech DMM's at $79 or more, have a 3 year warranty.

Eeh gads, the $129 EX470 has both Type K wired probe temperature -4 to 750C(-20 to 1382F) and a non-contact IR beam thermometer -58 to 518F (50-270C). As with flashlights, TOO MANY choices /ubbthreads/images/graemlins/smile.gif

http://www.extech.com/instrument/categories/multimeters/subcategory/multimeters.html

OT, but extech also has various light meters from $69 to the $249 EA33(which goes up to 999,900lux), and other expensive toys /ubbthreads/images/graemlins/grin.gif

http://www.extech.com/instrument/categories/light/light.html

 

[B@rt]

Another option would be E-bay, I got a nice Fluke 12 for $29.- .... /ubbthreads/images/graemlins/smile.gif

 

[markdi]

I love my tektronix tx3

 

[andrewwynn]

to answer a question above about the improvement of using your own shunt resistor..

any multimeter.. to measure current is actually measuring the voltage across a shunt resistor of a known resistance that is built in..

the error lies in that... there is typically just about as much resistance in the meter leads.. and that is not accounted for in the measurement... in addition.. depending on what you are measuring, especially if it's regulated circuitry, or load sensitive circuitry.. the meter itself can interfere with the values.

measuring voltage with a good DMM will almost never interfere with the circuit.. they are typically 30 million ohms or more.. so virtually no current flows.. but there is no really nice way to get around the problem of meter lead resistance w/o using an external shunt resistor.

textronix is nice stuff.. i'm still a big fan of fluke.. and BTW.. 'true rms' should help out with DC when there is ripple.. i know that i get solid measurements with the fluke with switching drivers that lessor meters have a problem with.

-awr

 

[KevinL]

That's the problem, meter leads aren't superconductors, which can really screw with direct drive lights. 0.4 ohm of resistance in the leads is all it takes to throw your readings off, with DD we tend to run them so close to the edge that all it takes is 0.2 ohms of resistance to balance things properly, not to mention another 0.4 to throw them wildly off.

 

[andrewwynn]

my first DD light... i was a little sad to see it only output 700mA.. thought my battery just had too much internal resistance.. well.. once i got the meter leads out of the equation... 1200mA is more like it.. what an amazing difference. Actually.. not sure if the 'cellphone' light outputs 1200.. probably more in the 1100 range.. it does have a couple inches of wire.. the 'microlights' however.. have zero-point-zero inches of wire... the battery contacts are wired to the lux leads and the switch which is directly wired to the other battery contact... now *THAT* is direct-drive.

http://rouse.com/flash has pictures.

 

[RussH]

This is another good reason for using a .1 or .01 ohm shunt resistor and taking a voltage measurement. Lead resistance won't have much effect on a voltage measurement since it will be a tiny fraction of the input resistance (several Megaohms, usually 10M on DMMs) and the current flow is very low. As Andrew said, the better meters (I'm looking at a Fluke 87III for my next purchase) often exceed 30Mohms.

To get better measurements, you need a wheatstone bridge which allows you to completely cancel the leads from the measurement. Analog meters do a decent job of that too, until you get into the under 1ohm teritory (where we are).

 

[sflate]

I'm selling a new Fluke 112 and case on eBay.

Here's the post

 

[wptski]

I have a Fluke 189 which I love that also does logging. I also have their FlukeView Forms software too. It's not cheap but a very good meter.

 

[andrewwynn]

:-D.. funny note about 10M vs 30M ohm.. guess i'm spoiled.. my 'low end' meter is the fluke 87 I.. my other meter is the 87III.. and i want to sell my 87I and get the 87V.. nice meter with thermocouple included. I find that for most uses of a meter.. the $5 DMM will actually do what you need... but lately with these pulsing DC switching boost and buck ckts, and with the high current nearDD circuits.. and LDO circuits... it's been really paying off to have some kick butt meters..

I especially like having two meters so i can have voltage and current at the same time to get accurate power readings.

I've seen 87IIIs sell on eBay for $100. I would sell my 87mk1 for that so i could use the proceeds to get the 87V.. which sell for about $280 with a good deal. I really want to get one of the fluke digital oscopes, though textronix is my fav. brand for oscope.

-awr