Bought a new DMM, got afew question's...

I am pretty stupid at electronic's, so bear with my inane question's.

I ended up buying a radio shack meter after looking at what was around town
in my price range.(a greenlee, wavetek/meterman, and a sperry) since the sperry broke
when i put the lead in I took it back, and got this model: http://www.radioshack.com/product/i...000094/&fbc=1&kw=multimeter&parentPage=search

It had the features i wanted, and felt stout and well made. I had been using an old shack pocket job for 10-12 yr's and it quit working, but always seemed accurate compared to my tech friend's meter's.

what I need to know is it accurate and how to tell. Since i am real anal about
thing's being relatively accutrate, I noticed that with the old meter my R123's would read
4.18 or .19 , my new one read's 4.17 sometimes flipping up to .18 but usually
settling at .17 .

Is this within a proper reading? i know one hundreth(correct?) of a volt is gotta be pretty negligible, but wanted to make sure.

The switchable auto ranging is nice and current measurement (the next question) But the battery testing section that put's a load on is pretty cool.

Also it's my first meter with a current setting, were do I put the lead's to say test a resistor in a DD 3.7 li ion/5mm mod to make sure it's were i want it?

I know most would buy a better pricey fluke or such, but $30 was my budget.
let me know so I don't keep wondering VDG

I've had reasonably good luck with RS; on sale they're often a good value & accurate enough for our hobby. Ignore the hundredth place for open circuit voltage of a cell - 10th are close enough for most applications.

Compare your readings to others known to be correct. Your meter should be OK. For $30 it seems like a good value for the features.

About measuring current: The red, + lead will usually have a separate jack on the meter's left side for checking amperage. Open the resistor's connection on one side and put the meter leads in series (one lead to the resistor & the other lead to the wire once connected to the resistor (or PCB solder pad). Your meter will tell you the total current going through the resistor and whatever's connected to it - sort of, depending on the circuit, but those are the basics.

Your meter is fine for $30, but for accuracy, you have to pay.

Your spec for basic DC accuracy is 0.8% +/- 4 counts in the 4-40-400 volt ranges. That means if you voltage was really 4.15 volts, your meter could read anywhere from 4.2 to 4.07, that is 4.15 plus .8% of 4.15 plus 4 counts in the least significant figure, or 4.15 minus .8% of 4.15 minus 4 digits. IIRC. And it's probably not guaranteed. But it might be better.

Look at a good Fluke 177 - 0.09% accuracy, +/- 2 counts. Almost 10 times better. Traceable to NBS. Maybe 10 times more money. It costs to make accurate A/D converters, RMS calculators, and flat AC response, etc.

Thanks Jayfish and louie for your consulting(yours louie lost me a little, but think you were saying the same as JF,) pretty much it read's about like my other meter (which was a real old DMM, and i bet less accurate) i did test readings in both AC and DC
since my meter is used mostly to set bias in tubes amp's, and for me or my guitar tech to check my gear, wall voltage and my variac i use on my amp's, all seem to be no more then 1/hundreth off if at all.

I shouldn't worry so much, I toured with Liz phair part of last summer and I saw showco techs(a large well known sound concert sound co) doing system checks with little cheap shack or no name DMM's :thinking: )

So thanks for putting my mind at ease and thanks and the current tips! peace. VDG

to test accuracy of subject meter, you really need a known to be accurate meter.

not everyone has a Fluke 87 freshly calibrated by Fluke to test against. so find a tech buddy that has a high end Fluke or simply find a Fluke dealer.

take along your meter and cell. test cell with both meters and you will know exactly how far off or on your current meter is.

it's not uncommon for meters to be off a few percentage. High end Flukes have the option of being delivered with a certificate of accuracy traceble back to standards. Flukes have reputation for accuracy. hince folks are more likely to accept readings from certain model Flukes.

here's pic of my electronics bench take a few minutes ago

cy said:

to test accuracy of subject meter, you really need a known to be accurate meter.

not everyone has a Fluke 87 freshly calibrated by Fluke to test against. so find a tech buddy that has a high end Fluke or simply find a Fluke dealer.

take along your meter and cell. test cell with both meters and you will know exactly how far off or on your current meter is.

it's not uncommon for meters to be off a few percentage. High end Flukes have the option of being delivered with a certificate of accuracy traceble back to standards. Flukes have reputation for accuracy. hince folks are more likely to accept readings from certain model Flukes.

here's pic of my electronics bench take a few minutes ago

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I agree, I do the equivilent with my strobe tuner's and calibrate with both guriarri, and neumann fork's.
As i mentioned i tested my old meter with my EE's bench unit's that are calibrated, and it was not off more then a hundreth or two. since this meter is on or within + or - one hundreth the last meter, as jayfish said, for our hobby at $30 it look's like it will be fine. I was actually more concerned because I will be using it for biasing my tube amps too.

cool bench! VDG

cy:

Looks like three Fluke 87 Series, correct? Why so many? The left one was left ON and powered OFF too! I already had a Fluke 189 but needed another DMM was going to get a low end Fluke but got a 87V instead. I also have a i1010, 65, 61, 54-II, 88V, 80T-IR, 1507 and a 971 on order. That's just the Fluke stuff. I'm a tool guy!

Fluke 87 on left is set up to measure current, middle meter measures voltage and right meter measures output of 15amp HP bench power supply.

middle Fluke 87 has just been freshly calibrated by Fluke. odds are when I take reading, it's dead on

cy:

What's Fluke charge for recalibrate?

voodoogreg said:

.... i did test readings in both AC and DC since my meter is used mostly to set bias in tubes amp's, and for me or my guitar tech to check my gear, wall voltage and my variac i use on my amp's, all seem to be no more then 1/hundreth off if at all.
.... VDG

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Right. The big problem in low-cost meters is not basic DC accuracy, but AC accuracy. They have poor frequency response and often aren't rated at anything over 60Hz. Also, they are only set to give an AC voltage reading of a sine wave, any other wave will be wrong, unless it has true RMS sensing. However, that's all many people need.

While I too enjoy lots of digits and high accuracy (same as I like rifles more accurate than I can shoot...), I hasten to point out that we put men on the moon with Simpsons, log tables and Sliderules.

Precision, resolution and repeatability are all fine in and of themselves, but it's only a tool in the end.

Doug Owen

Well a simple question has turned into a worry i wasn't gonna deal with for too long. just got back from my long time tech's shop (thank God he ws in town.) and got the skinny on my non fluke cheap a$$ meter.

first his resume: MIT grad 79', currently head acoustic engineer for Harmon kardon US east/japan. formerly US navy electronic weapons tech, head of delco-remy auto electronic ignition and CPU design system's, well known vintage/tube electronic's consultant.

Well I told him my story, and since he's a mean old fart got a lot of pleasure from my worry. But I have known him since about 19 when I brought my first in a long line of blown plexi marshall 100 watt amps.

anywoo, he took my meter ran it with 3 hand held metter's two fluke's and nagra then to a large box on his shelf. His opinion was great little piece of junk meter (RS meaning junk)
it stayed consistent to tolerance in all range's including my feared high VAC need's, and stayed stable/consistant with the nagra and fluke's at high VAC.

These are his word's not mine (keep in mind he's a dear friend and testing flashlight circuit's probably seems beneath him, and he love's to harass people :naughty

"see these? these are real meters, agilent's and boschs made in germany,
since I have been repairing your crap since you were a pup, and seen your soldering skills if that's what you'd call it, so If your gonna cut hair's even this 30 buck RS DMM is above you! take my word, tell your flashlight
nerd's to step up, or step off my deck. the company sent me these two flukes certified from some idiot from the factory neither match. Nor do that match "my" meter's those two agilent bench unit's do,, without so much as a flicker! at any range or function. Same with the bosch and hand held nagra,
Oh, did you get my Christmas card? no? that's cause I don't send christmas card's!"

So I feel a lot better about my meter!

After the abuse,, he gave a me a cool not on the market HK/sony joint venture thing a hard disk field recorder that's about the size of a pack of smokes but slimmer, rechargeable, with 200 gig mem and three port's for down loading on flashcard, jump drive, or PC. I kinda forgot about my new meter and have been playing my new cooler toy.

None the less thanks for your help and opinion's. VDG

VDG:

HK sent him the two Fluke's which a guy at "HK" certified, correct? Not Fluke?

wptski said:

VDG:

HK sent him the two Fluke's which a guy at "HK" certified, correct? Not Fluke?

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No from fluke.
He said "some idiot from the factory" the one paper I saw said "fluke" on it.
They came from fluke bought by HK for fergie who has some motion field work
coming up at IMS. He "stole" the Nagra from his office in japan because
he wanted what he thought is a better meter on the IMS test's.

The big picture here is a) i turn mole hill's into mountain's sometimes and he's a great "leveler" And in all honesty we all often get a little anal about our tools and toys me too, I have $4000 amp's that only i can here the extra
5% pleasing tone an audience wouldn't, and I could live with what a $1000 amp would do. and we all have personal pref's. I will say those agilent's were bad ***! looked like space shuttle stuff but prettier!
ferg's a trip but a very nice guy under it all, so fluke user's relax! VDG

OT but I love the way tubes help a guitar sing. Still using an old Dyna Mk. IV knockoff/mod: the Sunn 200 - S.

jayflash said:

OT but I love the way tubes help a guitar sing. Still using an old Dyna Mk. IV knockoff/mod: the Sunn 200 - S.

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Great amp! They just re-issued the sunn 100-200's albeit with a PCB (as you know, some don't, but guitar players that dig amps circuit's usually prefer hand wired, PTP. After a few yr's they seem to burn in and get sweeter and more harmonically rich)

Hell one of best tube amps i use in session's is a silvertone that was orginally built into the guitar case! sold them at sears back in the 60's. VDG

That tech sounds like a hoot! Not unusual-I think I know a lot of people like that.
I still maintain you get what you pay for; I bet those Agilent voltmeters have specs for DC accuracy 100 times better than most Flukes - and cost $1-2K. And just because 2 units match doesn't mean either is correct. Fluke & Agilent should be capable of delivering units meeting published specs when calibrated, traceable to NIST (was NBS) standards. Whether someone messed up, or were actually calibrated and met specs, but didn't match, who knows.
Your RS unit sounds like it exceeds its specs!

I've seen calibration certificates start at $150 & go up from there.