analog multimeters

[Strogian]

I was thinking about getting an analog multimeter, not necessarily for audio use. (but I bet I'll be using it on an amp eventually

) So, naturally, I look for the absolute best of the best to see what is possible, and I see that Simpson and Triplett have made the "industry standard" meters, essentially unchanged since world war II. But new, they can be in excess of $200 ! Even used, (without even knowing if they work or not!), people will pay $50-100 (plus shipping!) on them on ebay.

So I look at the cheapest radio shack product:

Analog Display Compact 8-Range Multimeter

$10. That's more like it.

The lowest volt scale is 15V, it only measures up to 150mA of current, and only a 100Kohm resistance scale. (more expensive ones go down to e.g. 150mV DC, and they might go up to 100Mohms for resistance) And the input impedance is only 2Kohms/volt. (compared to 20Kohms/volt with normal analog meters)

My question is, how will these shortcomings affect what I'm doing? What kind of measurements might this meter not work for? (of course, things requiring 0.001% accuracy are impossible for ANY analog meter, so I'm not too worried about the 3% error I'm getting) What can other analog meters do that this one can't? Is there anything I'm missing, that I'll get with the expensive meters that I don't get with this? I even read the specs and the accuracy is rated to 3% of full scale, like most of the expensive meters. (the best are 1.5% -- not much difference) The 2Kohms/volt is the main worry I have right now -- normal analog meters are 20Kohms/volt, and I'd like to have a normal impedance if possible (I hear some old radios and whatnot are spec'd using a 20Kohm/volt meter). But I don't know how important that really is.

EDIT: I'm shopping around the internet now, and this 2kohm/volt sensitivity seems to be pretty common in the <$10 meters. hmmm

 

[nleahcim]

Why would you get an analog multimeter? I find them to be simply miserable to work with.

 

[superjohnny]

I got my digital multimeter from Fry's for $20. It measures resistance down to .01k ohm and higher than I can ever imagine myself needing and it measures ac/dc voltage to withing +/- 1v. PLUS it comes in an indestructable ugly yellow plastic case so when you're pissed you can throw it instead of your CMOY

Do you prefer analog?

 

[Demolition]

Strogian,

I have to agree with nleahcim and superjohnny; you'd probably be better off with a digital multimeter. They provide far more accurate and consistent readings compared to analog MMs.

$25-35 US will get you a good basic DMM for DIYers. Maybe take a look at the offerings from companies such as WakeTek, BK Precision, or Extech. They're known for making good quality, affordable DMMs. Moving up the price-scale (or choosing from a high-end company such as Fluke) gets you more features and better accuracy and precision, but it doesn't sound like you want frills.

D.

 

[Strogian]

I'll tell you why I like analog: I understand them better.

I have a VERY BASIC understanding of electronics, and that's all I need to know exactly what is going on in an analog meter. Well, not EXACTLY, but a good idea.

And one thing I hated about the DMM (radioshack, not cheap) I had before burning out god-knows how many things in there ... when I am trying to take a reading of something, but it does not stabilize on a value! I hear analogs are better at showing trends, and I believe that! Maybe it didn't stabilize because there was NO stable value, but I can't trust flashing numbers to tell me that.

And now that I think of it -- I don't even know if my DMM works or not. It puts numbers on the display, and they don't SEEM right most of the time (sometimes they do!), but I just can't tell. And I have no faith in it anyway.

I really am pretty set on getting some sort of analog, it's just a matter of which one. Maybe I'll just go ahead and get this cheapie until I find out what I actually need one for. That's what radio shack is there for, right?

 

[Sync]

You might want to check out walmart if you want cheap ones. I dont know what they do or how good they are but I do know they carry at least one dmm (which i have) and one vmm. the digital is around 18$ and the analog is...I dunno...cheaper.

 

[tangent]

Quote:

how will these shortcomings affect what I'm doing?

Input impedance: Imagine dropping a 2K resistor into your circuit: its behavior will change. At best the circuit will continue to function but you'll have to correct for the voltage drop you create. At worst it will make a good circuit fail, or a bad circuit start working; neither is helpful. Even a 20K impedance is low enough to cause noticeable changes in your circuit's performance. A decent DMM will have an input impedance up in the megohms range -- negligible loading of the circuit.

Accuracy: To some extent, high accuracy is pointless with analog meters. There's only so small a movement of the needle that you can discern. But, a 1.5% accuracy does mean that you won't be hand-matching resistor pairs to 0.1%.

Quality: An expensive meter will have better build quality and better accessories. With VOMs, you get a bigger dial, hence more accurate readings.

Repair and calibration: With cheapie meters, if it breaks, you can only buy a replacement. Worse, what you get out of the box is not guaranteed to any useful spec of calibration. You're on your own all the way with cheap meters. A good meter can be purchased calibrated, if you keep it calibrated you know it is still in spec, and if it breaks you can have it repaired. The latter means you won't find repairable meters costing less than about $100. There's just no point, since a repair job costs around that much.

Quote:

I hear analogs are better at showing trends,

This is true, which is why it's a good idea to have an analog meter on hand for the occasional time where it's helpful. I wouldn't make it your only meter, though.

Quote:

I don't even know if my DMM works or not.

If you'd get a name good brand name meter and have it calibrated regularly, you would know it worked. "Radio Shack" doesn't count as a brand name.

 

[Demolition]

Yes, analog meters sometimes react more quickly than DMMs. DMMs take several measurements per second as they try to pin down a value which, as you noticed, causes the DMM to hunt around a bit. After a second or two, it should stabilize unless the input signal is variable. In that case, as you said, it's sometime easier to see the trends visually than to scribble down numbers from a DMM's display.

Maybe another place to look for analog multimeters is at Home Depot. I recall seeing a few in the electrical section at my local store, ranging in price up to $39 CDN (~$30 US). I also vaguely recall that they had a mini multimeter for $9.84 CDN (~$7.68 US). Personally, I don't think I'd trust it. It looked extremely cheap (i.e. like cheap-crap, not cheap-inexpensive).

Going back to DMMs for a second... one way to get around the problem of blowing up components (or the DMM, as might have happened to you) is to get an autoranging DMM from a decent company (not Radio Shack

). You just have to set the dial to a function (i.e. voltage, capacitance, etc.) and the DMM automatically sets the range for the input signal. No worries about mistakenly choosing the wrong range and frying stuff.

D.

 

[Demolition]

Quote:

Originally posted by tangent Input impedance: etc.

Damn, scooped me by a measly 3 minutes, Tangent.

D.

 

[Strogian]

Quote:

If you'd get a name good brand name meter and have it calibrated regularly, you would know it worked. "Radio Shack" doesn't count as a brand name.

Quote:

get an autoranging DMM from a decent company (not Radio Shack ).

Great.

About calibration, how necessary is that? Through normal use (i.e. not stressing the meter with a bunch of rough measurements), how far will a good meter from, say, Fluke drift? Would Radio Shack meters (or even good analog meters) drift more than a good DMM? Or is it just good for fluke's that you CAN get them recalibrated?

And.. can you do it yourself, without having to pay anybody?

Actually, all I'd probably care about if I had a good DMM was that it was consistent. I'm not publishing my measurements in an engineering spec -- I'd just want it to be consistent and sensitive enough to match components.

But with an analog, "it's about 4 volts" will be enough for me!

EDIT: I actually will probably want something with some smaller scales than 15V, though.

EDIT: oh, wow! I see a good deal online, from a SUNWA brand meter. But then I do a little search for SUNWA, and find out there is actually a company called SANWA that makes meters. Now I don't want to buy it, if it's just a SUNWA.

 

[Trawlerman]

It's been a while since I did any major DIY projects. Probably going back 3-4 years now.

However, I do remember that you have to be very careful with multimeters as in some cases the internal battery in the multimeter will start to give of a voltage that can easily damage ICs and Transistors etc.

I'm sure it was when testing Semiconductors with Analog meters. Maybe one of our more seasoned users can pick up on this.

 

[bigcat39]

OK, read tangent's post. Now read it slowly. Read it again. Analog meters have their place..... if you fill the case with enough cement, they make dandy rowboat anchors.
Analogs are damn near impossible to keep in calibration, even a Simpsom 260, which is the lead, er, gold standard for VOM's.
I'm still going to advocate Fluke handhelds from Ebay, if they break, Fluke charges a flat fee to repair them, $60 - $100 depending on model. And all they do is open the case and replace EVERYTHING in the meter, if the case is broken, they just give you a new meter. Hard to beat.
Is calibration necessary? You bet! An illustrative tale: My work Oscope, a ~$45,000 model from Agilent, came up for cal recently. When I attached it to the standard, I discovered that the input attenuator in one range had gone from 50 ohms to 80 ohms. There was no way for me to know this, and I'm an electronics metrologist. It threw readings for that range off by about 40%. If you don't have your meter calibrated, you might as well just guess, because you aren't measuring.
Can you calibrate it yourself? Hmmmm, the machine I use to calibrate meters is a Fluke 5700/EP plus a 5725 amplifier. They go for about $75,000 for the pair, plus $50,000 for the standards to support them, and a $2,000 calibration verification every 2 years, plus $3,000/year for calibrating the standards to check the thing every 90 days. You can get by with less, but......
Commercial cal labs charge about $50 to cal a handheld these days, ahhhh the wonders of automated test.

Tangent .. you sound like a PMEL trained person...are you? And if so, do I know you?

 

[AndrewFischer]

>>So I look at the cheapest radio shack product:

Those cheap analog meters are miserable.

The scale is tiny and hard to read. The 2K ohm per volt makes the meter useless in many cases. Most of them don't have fuses or over voltatge/current protection and are easily destroyed. And they are inaccurate.

I've used a Simpson 262 many times and it is a far better tool. 20K per volt is still a bit limiting compared to what you can get from a DMM, but the error introduced is usually minor. As previously mentioned, the higher resistance scales on the 262 put out enough voltage to destroy some semiconductors.

Back when the 262 was still common, I spent the $$$ and bought a Beckman DMM. I've never regreted it.


I've seen used high quality DMMs like my Beckman go on eBay for $10-$20. I recently picked up an old lab-standard analog voltmeter on eBay. Cost me about $30, mostly for shipping. Originaly was accurate to 1/2%. The thing still works and may still be close to that 1/2%. But it is a pain to use and mostly just sits in a closet.

 

[tangent]

Quote:

Would Radio Shack meters drift more than a good DMM?

Since low-drift components cost more, I would expect that a cheap meter would drift more than an expensive one. I don't know this for a fact, it just seems evident to me.

Quote:

can you do it yourself, without having to pay anybody?

If your calibration equipment were no better than the meter you are calibrating, why would you believe the results? Or to put it another way, if you had equipment good enough to calibrate a meter yourself, why wouldn't you just use the calibration equipment to do your measurements? (This is a low-end view. Obviously you wouldn't use bigcat39's multi-kilobuck setup for building headphone amps.)

Quote:

sensitive enough to match components.

Since cheap analog meters can't do capacitance and you can buy 1% resistors for pennies, you must be talking about matching resistors to less than 1%. Since your meter has to be more accurate than what you expect to measure, you'd better have a pretty darn accurate meter.

Quote:

Tangent .. you sound like a PMEL trained person...are you?

No, just an avid hobbyist.