Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Nice reply except for this bit of baby bullshit.
You might need to f*ck off and die.
No FET front end on that!
Bwuahahahahah!
I had one too.
An indirectly heated cathode Field Effect Tube.
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.
-- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you\'re crazy.
So, you don't use current transformers or clamp on AC ammeters?
If you are working in dangerous locations without the proper training you are likely to die. If you are properly trained, the company supplies the proper equipment needed to do the work. If you work for some fly by night schlock outfit without proper training an safety equipment OSHA won't collect a cent, because the owners will flee the scene before they arrive, and have nothing worth seizing, anyway. the last time I heard of someone working with HV dying, it was a nine bucket that was working in Florida to help restore service after hurricanes, when some idiot hit it when the crew was on its way home, and cause it to roll off I-75 in North Florida.
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You weren't discussing, you are posting old wive's tales. Power generation has nothing to do with portable meters. Current transformers and voltmeters are permanently installed at each generator so the can monitor and balance the load on each alternator.
-- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you\'re crazy.
f
So it's a vacuum tube front end instead - same thing, same result. A fixed 11Mohm input, not 10M/volt as you foolishly claimed.
Dave.
"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.
!0 M Ohms will not load the circuit under discussion enough to clamp local noise either.
The problem is an idiot that HEARS a "fact" from someone, and goes with it as bible whether they know the whys and wherefores or not.
That is why the dope that thinks a DMM is a bad tool to use in certain setting is too damned sparky retard stupid to grasp the science involved. Because some other dope told him so, and he NEVER bothered to understand the deeper reasons as to why the declaration was made or how such a tool could be used properly in the setting under discussion.
In other words, the arlowe disphit doesn't know the science. He is only going on what has been related to him over the years, and he has no grasp as to actually WHY one meter is better than another for a given test circumstance.
Some people work with electricity their entire life and never really understand it. There are dozens of basic voltmeter types, and you need to know enough about them to use them properly. Have you ever used a frequency selective voltmeter? How about a field strength meter? A true RMS voltmeter that will display a .01 dB change at up to 20 MHz? How about a Vector Voltmeter, or a Differential Voltmeter? One of the old HP AC VTVMs that read voltage well up into the VHF range? There are lots of specialized meters out there.
What is wrong with pointing out that there are other, and better tools for the job? I built a radio at eight years old, and really didn't understand a lot about how it worked, but I did make it work. At
13 I was repairing radios, working part time in a TV shop. I went straight from high school to working at a TV bench. I have a poorly built Eico 1000 Ohm per Volt multimeter someone gave me. I'll redo all the bad solder work some day, but I would never actually use it for anything. I use a DVM for electrical work, and it is the meters from my electronics bench. I've used it to troubleshoot things wire pullers couldn't figure out with their meters. Instead of get a 'thank you', I was told off. OTOH, they had spent half a day trying to decode a bundle of wires in a crowded conduit. I identified and tagged all the wires in less than 15 minutes.An equivalent to the specialized voltmeter for wire pullers is the cheap CATV field strength meter with a few LEDs to give a basic Go/No Go test for cable TV installers. It takes 30 seconds to train someone off the street how to use it.
And common sense.
Er work with HV armored cable? You can't see the insulation, because it is made like Heliax, with a polypropylene filled insulator. A real bitch to cut, strip and terminate. Do it wrong and you have a spectacular fire.
Only for those who don't understand how to read a real meter. That's most users, or they wouldn't make so many of the crappy things.
A clamp on meter is safer and more accurate to read the current in a working circuit. They are fairly cheap these days, too.
The bigger problem is ignorant trolls who infect every thread, spouting garbage. Unfortunately, these bottom feeders are growing in numbers. :(
-- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you\'re crazy.
"Michael A. Terrell" wrote in news:ab- dnX9LJ9G4suDUnZ2dnUVZ snipped-for-privacy@earthlink.com:
Reminds me of the teacher who told me at age 7 to show my workings in long multiplication and division. As soon as I had to do it with their formalism I stopped being able to do it as fast. Didn't matter that I was right, didn't matter that maybe a kid who had something good should be encouraged to develop and explain it even though it didn't fit the model. We're lucky. One time they'd have screamed BURN THE WITCH and done it too.
"Michael A. Terrell" wrote in news:ab-dnX9LJ9G4suDUnZ2dnUVZ snipped-for-privacy@earthlink.com:
Notoriously rare, allegedly. :) In something like 'phantom' voltages in unconnected lines in power distribution, it might be considered that it goes way beyond ohm's law, as inductance and capacitance are involved, but my 'common sense' tells me to try to reduce to Ohm's law where possible. So for simple tracing of lines, a light load is enough to reduce the values of indirectly coupled voltage. I'd rather have more control of what load I choose than leave it up to whatever is supplied in a meter, but that's just my choice. At least this way I have the option of putting it in series with the meter and measuring current.
No, never done that. But I try not to walk blind into situations like that. The only time I did get a copper vapour deposition of some strength across my eyeballs was after someone else had gone in and royally blown 100A cables apart first so the resulting mess made it very hard to figure out what the state was, on a circuit that could not be isolated within reach. All it did was confirm what I already knew: that my own assumptions are the best place I can fix an error before it goes bad. (in this case I assumed that two separate lumps of brass could not have been welded into one through a thick thermosetting plastic layer by the actions of a guy who had shorted them with only a momentary contact with a 2.5mm square wire. To this day I don't know what demonic persistence he used to manage that much destruction, all I know is it can't have been momentary, he must have been feeding it in like a welder).
True. Electricians do have a point though, I tested this last night with a Fluke 79 series II. Its input resistance is high, but not the type of high that prompted the OP to post. I knew that when you have a moderate length of corridor, say 6 metres, with a lamp that has a switch at both ends, you have a very standard situation where a line is unconnected in a cable when the lamp is on. Which line it is depends on which positions the SPDT switches are in to close the lamp circuit. I noticed that the capacitatively coupled voltage on both lines was identical, at least, differences were lower by far than line fluctuations. This is probably the sort of thing that angers the electricians when someone claims a meter with high input resistance can be used. In this case it can't, alone. But I'd still rather have a separate load to apply, than have to use more than one meter. A 200K resistor seems about right (for circuits up to 500V), as in this case there is only the earthed switch box to reference to, and any more than a few milliamps would probably trigger an ELCB somewhere...
Lostgallifreyan wrote in news:Xns9B9F30780727Dzoodlewurdle@216.196.109.145:
Too clumsy an edit to let pass... ONE of them was directly coupled.
te:
ble.
It should be clear the discussion is about high available fault current - the current you get when the source is short circuited. This is a really basic concept in design and protection of high current AC power circuits. (But it may not be something you have run across.)
High available fault current can result in arc flash. Arc flash can result in major injury and death in addition to major equipment destruction. Arc-flash is estimated to kill 200-300 people a year. OSHA has made arc-flash an issue. Safety protection may require wearing an arc-flash suit.
One of the smartest electricians I know was seriously injured by arc flash. And it was through an equipment failure - he made no mistake.
The issue I raised is appropriate meters. As I wrote above, the IEC has measurement Categories I-IV. If working in high energy locations, like panel boards and services, the appropriate meters are Cat III and IV. These meters are designed for the riskier environment and have better transient withstand and fusing.
My analog Triplett 310 has a glass fuse. I have a Beckman digital that has a similar fuse. They might be safe in Cat I. My Fluke is rated Cat III and IV. That includes transient withstand well above the nominal voltage rating and high interrupt capacity fuses.
OSHA might be real displeased if the wrong meter was used. And when OSHA is unhappy you might be unhappy.
If you didn=92t assume everyone else was an idiot you might actually learn something. (But probably not Archimedes.)
-- bud--
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--
Which is NOT a problem with ANY modern meter.
In other words, IDIOT... EVEN IF IT FLASHES IT WILL NOT CAUSE A HIGH CURRENT INCIDENT.
Two simple premises, dopey f*ck.
ONE: The meter leads are SMALL gauge! Do you even know what that means?
TWO: WHERE is the short circuit, IDIOT!?
HIGH VOLTAGE arc flash kills 200 to 300 people a year.
Low voltage arc flash, not nearly as many in that statistic.
When you express statistics, you should be careful not to massage them to make your position appear stronger. It will always bite you in the ass.
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.
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