Freaky Amazing DMM?!

Only if you don't know how to interpret the better meter. Its a dumbed down toy for wire pullers. I've seen too many over the years that couldn't find an open neutral, or bad connection unless it was on fire.

If you are reading 83 volts, either it is a phantom voltage, or you have a 40 volt drop in a 120 volt circuit, or 160 volt drop in a 240 volt circuit, which is damn unlikely. If you can't see this, you don't know what you're doing.

The appropriate tools start with a well trained brain. Otherwise, you are a monkey throwing crap at the problem.

If is working with what you described, it certainly won't be 'low impedance', because the the current flow required, times the voltage being read would be so high that the meter would need to be in a 55 gallon drum of transformer oil, and able to dissipater several kilowatts. All this would weigh several hundred pounds.

My experience is a broadcast engineer, (The largest was at a 5 MW UHF TV site.) industrial electrical work, and specialized electronics that you'll never see, without going to the International Space Station.

"Michael A. Terrell" wrote in news:rOWdnQ1TB4W1kOHUnZ2dnUVZ snipped-for-privacy@earthlink.com:

And both extremly impressive too, yet apparently in disagreement.

I don't think that high an experience is needed to understand this anyway, I learned it at 14 when an aging friend of the family taught me how to build my own (and first) multimeter.

Ohm's law.

And a bit of awareness of insulation strength when high volts are involved.

If you're using a low resistance input you might have to take it into account for accurate measurements but on mains, the error is small, so it's worth keeping inputs resistance low for meters dedicated to such systems, for reasons plenty of posts have explained, so I won't flog that horse now.

If you have strong insulation, you can probe an HV circuit without trouble, just make sure you understand what the meter says. If a meter designed to tax the system as lightly as possible says 83V it means 83V, the problem isn't the meter, you just have to know enough to interpret the truth it tell you. (Mike Terrell got this one right). If you also need to know current through the same meter, you could do it by measuring small voltage across a part of one conductor, then measuring resistance of that part after removing power. Most current meters just do this internally anyway, but they 'know' the resistance of their shunts so they calculate correctly anyway.

So the question isn't who is the most experienced, it's who is right? And take care, because if two people with real experience start arguing over something as basic as Ohm's law, they'll do each other's reputation harm, as well as making it hard for newcomers to trust what they read here.

Is it a phantom voltage? Do you have an open neutral? Voltage coming back through another device? One of many other possibilities?

Arloe can eliminate one of them real fast because he knows what he is doing.

How fortunate that Arloe and Stewart and I are well educated and know what we are doing.

If you followed the thread you might understand how =93low impedance=94 is being used.

-- bud--

Easy enough to identify.

I would have full voltage on the supply side.

Not difficult to troubleshoot.

How about high harmonics on the neutral of a three phase service in an office or server room? Do you know why the neutral has to be larger than the supply lines? This has been well documented for over 25 years. Buildings wired to earlier NEC codes have had major electrical fires.

All easy to troubleshoot, if you have common sense and a true understanding of electricity. Try working in a 'zero downtime' job sometime, where you may only have seconds to find a problem to avoid costly repairs, or expensive damage to the entire facility rather than simple monkey work where you can spend hours or days tracking down a problem. Places where preventative maintenance can save lives.

So can I. I've done it for over 40+ years.

Sure you are. Yet you can't figure out how to do it without a dumbed down tool.

I followed the thread, even though it loops in multiple, ridiculous circles. Either you can work with available tools, or you need your hand held, and your mommy to wipe both ends for you.

Even easier for Arloe.

It=92s the favorite nobody-knows-anything-but-Michael argument.

Not the issue, of course. Any tool can be used. The question is what is appropriate and efficient. High z meters do not help you on power circuits, but you can use what you want. Arloe is entirely reasonable to use a low z meter.

-- bud--

Proof that its easier for him?

You are starting to sound like your hero, the cut & paste 'surge protector W_Tom'.

Arloe can use anything he wants to. No one else cares, but a lot of what he posts is old wives tales.

Bullshit. Prove me wrong.

It is not uncommon to read mains voltage, not some BS 83VAC like some have referred to, but MAINS VOLTAGE on a conductor that is isolated.

When you have a panel where the active cables are segregated form the neutrals, you can get very strong, alternating magnetic fields depending on the current draw.

If you put an isolated cable in that field you will measure voltage on that cable with a DMM. An electrician can not rely on reading an "incorrect" voltage as an assurance that the cable is dead. He has to be able to PROVE IT. Some will use an analog meter, I don't, I use test lamps that have the correct CAT rating for the enviroment. I follow up by testing my lamps on a "known supply" ie. a supply that I verified live before I performed any testing, just to prove the test lamps are functionimg as intended.

Call it crude, I don't give a f*ck, it works, it is failsafe and it is fast.

So does a screwdriver against the case, and to a buss bar, but I won't do it.

??????? Don't be stupid.

I don't want your job. You're the expert at stupid.

Actually it does cause false voltage readings even in circuits with no "loose nuts". You can connect the meter to a point in the circuit that is open somewhere, perhaps because of an open switch contact, and you get false voltage readings that can range from 10V to close to line voltage due to stray pickup of the wires. It causes electricians to sometimes misdiagnose problems, and it causes confusion. I often demonstrate this to my training classes so that they are aware of it.

This is an unavoidable and unfortunate side effect of high impedance digital meters. You need to understand it when you use them so that you can question and investigate readings that don't make sense.

Analog meters don't have this problem, but they are disappearing because the analog circuits can not meet the necessary safety standards.

Ben Miller

You mean that cheap analog VOM had low impedance inputs. There were millions of VTVM and FET input analog meters with a 10 Megaohm input impedance in use over the years, and a lot are still in use.

Of course not. The "loose nut" is the one interpreting the measurements.

Right. The typical sparky is clueless. This fact has been demonstrated here endlessly.

It certainly may be if you're clueless.

"Analog" has nothing to do with it.

Those are great on a lab bench, however very few were ever used for industrial power measurements. FET inputs are not notoriously rugged, although they could be used if desired. It is difficult to run an extension cord for a VTVM out on a factory floor, not to mention the smoke that can escape when you apply a grounded test lead on a power system measurement, assuming that you survive to talk about it :-(

You will not find very many analog meters with an IEC CAT rating, with good reason. The typical analog industrial meters such as the Amprobe RS series or the Simpson 260 series have resistor networks on the inputs, and very likely don't have the requisite creep and clearance distances in their construction. There are also problems with the Ohms circuits. One of the IEC requirements is that you can safely apply maximum rated voltage (ie. 600 or

1000 volts for example) to the meter inputs with the range and mode switches set to any setting. The meter doesn't need to continue working, just fail safely or do nothing. Many meters have fuses for the amp ranges, but analog ohms circuits can fail catastrophically if high voltages are applied to them. The manufacturers just can not justify the redesign of those meters to meet the safety standards.

Ben Miller

Some VTVM had a built in battery for portable use. They were rare, but they existed. They used subminiature tubes with a 1.5 or 3 volt filament like those in early hearing aids.

The 260 is a dinosaur, over price instrument in today's work environment. Even if it was modified and certified, it would be sold to a niche market and not worth the engineering costs.

The early FET input analog meters I've used would die if their was a tiny spark when probing. If they had a small choke on the input to filter the RF, they were fine, but it would void the certification.