Looking For Usable Multimeter - Cheap

Well, that's what the FLuke bench DMMs are for. ;-)

Jeff

Actually some were HP 5+3/4 digit with IEEE-488 interface to verify calibration.

Thought the question was about the spec for a basic DVM?

As regards a bargraph being 'visual noise' that's the whole point. It draws your attention to the direction and rate of change. If you're using '30 pieces of test equipment' at once, you can't possibly read them all accurately at any one point in time - so a bargraph sounds to me even more useful here.

This discussion reminds me of the article on digital voltmeters in "Electronics World" about 50 years ago.

Back then, they were huge, taking up (if I recall correctly) a 3U or 4U space. The meter they described was a Non-Linear Systems model. Its ADC was electromechanical, (!) using a relay-controlled voltage divider on a highly-accurate voltage source to create successively closer approximations to the input voltage.

There were no commercial LED displays, of course, so the results were displayed using incandescent lamps to side-illuminate numbers cut into polycarbonate blocks! (I don't know why NLS didn't use Nixie tubes.)

Maybe, if you want to be distracted. I was testing modules in $20,000 to $80,000 (US) telemetry receiving systems. The 'Video Combiner' module compared the linear 0-5V AGC buss in two receivers, and was allowed an error of under 1.5 mV.

I wouldn't use any meter with one on my bench, but some techs wanted them even though they were useless. They also clutter their benches with piles of other useless crap. Tell me of ANY bargraph that will give useful indication when the change is in millivolts, where the voltage being measured is 5 to 15 volts. The bargraph would be 2 volts per division. The bargraph driver is noisy enough that the display is unstable at the boundaries, and some are used with an overlap to reduce flicker. it does this by dithering the reference voltage.

HP made a voltmeter plugin for their 5245L frequency counter. That was mid '60s vintage.

I think it's rather finer than that. (My Fluke 87 has 51 points.) But no one (that I know of) makes a DVM with that can display millivolt changes when the input is hundreds of millivolts.

The purpose of the bargraph is to give the tech an easily interpreted indication of which way the measurement is tending, without having to "interpret" the numbers. And it responds much more quickly than the display can settle.

I have little need for the bargraph display. But it adds little to the cost of the meter, and it's there when I do.

Interesting. I had an SWTP modular unit, though that was a lot later.

The NLS appeared earlier, I believe. George Kay (as in Kaypro) is given credit for the first digital voltmeter.

Fluke meters have a bar graph and I find it usefull.

God for you. I never have. BTW, it's spelled useful, with one 'l'.

I used meters like a Boonton 9200, a Fluke 8920A and several 4.5 digit or better general purpose DVMs. The signal generators and frequency counters were all connected to the in house 10 MHz frequency standard and we had an in house metrology lab.

And Good is spelled with two "O"s

Per Shaun:

---------------------------------------- Eye halve a spelling chequer It came with my pea sea It plainly marques four my revue Miss steaks eye kin knot sea.

Eye strike a key and type a word And weight four it two say Weather eye am wrong oar write It shows me strait a weigh.

As soon as a mist ache is maid It nose bee fore two long And eye can put the error rite Its rare lea ever wrong.

Eye have run this poem threw it I am shore your pleased two no Its letter perfect awl the weigh My chequer tolled me sew.

----------------------------------------

I never claim to be perfect.

Just as well. ;-)

--

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.

When someone claims to be perfect, I ask to see the nail holes.

On 2/28/2011 11:51 AM Michael A. Terrell spake thus:

Ha!

Your one-line responses are generally annoying, but this one's a zinger!