Yes, electricians generally just do just the one similar job. That's why they make meters designed for just such specific purposes. Giving your average electrician say a Fluke 289 is a bit overkill and would likely not be as productive as a more job specific instrument.
That's why many good meters have selectable Low-Z and High-Z modes.
Dave.
Safely, in a dangerous situation? What part of using the right tool for the job don't you understand?
Yes, High-Z meters are good (more useful in more cases), but Low-Z meters have their place too. There simply isn't any argument here, if you need a Low-Z meter, use one. If you need a High-Z meter, use one. "Making do" without the right tool in serious situations is stupid.
Agreed. That's why if you have serious needs you either have a dual purpose meter, with Low-Z and High-Z modes, or you have two meters.
Dave.
Daniel wrote in news:e8f56b53-9c0c-49cd-b6b5- snipped-for-privacy@i24g2000prf.googlegroups.com:
I thought it was to do with a craftsman knowing the limits of his tools, thus not blaming them for over-reaching.
Related to that, I find the best definition of a toolmaker is one who achieves greater accuracy than was provided, and makes a system to easily repeat that gain.
It's easy to do safely.
What part of understanding electricity don't you understand?
If you're a sparky and all you do is wiring, sure. There is no reason to have a high impedance meter. That doesn't mean that a high impedance meter can't be used safely and accurately.
If you have a meter for every job, sure. If you don't, a little knowledge goes long way.
Nice snip. That's known as a lie in many corners.
No, you understand what you have and use it appropriately. ...something there is an obvious shortage around here.
claims *over*
impedance" or "HI-Z"
That wasn't at issue here. The statement was made that a high impedance meter couldn't be used and that a low impedance *ANALOG* meter was a necessity. It's certainly not true, though one has to understand what one is doing, again a rarity in this group.
Most *good* meters don't. Many sparky meters might.
Ok, I haven't followed the entire silly thread. From my side I've only been proposing that high impedance meters can be a problem, and the solution is using the right tool for the job.
Dave.
No, that's the backhand side of the expression. He doesn't blame his tools because he understands when he makes a mistake it's his. Hackers blame everyone else, and the tools (even if they have the best).
Yes, they can be a problem if YOU DON'T UNDERSTAND WHAT YOU'RE DOING. If you know what you're doing you can get the right reading form a high impedance meter just as well as one that has been crippled by the manufacturer. If necessary, you can cripple it yourself, though that is rarely needed.
The same with ANY measurement instrument, nothing unique here at all.
Crippled? Hardly the right term, try purposely designed. Just like you wouldn't go around saying a meters DC range is "crippled" because it's 0.5% when they could have made it 0.1%. Or a meters current range is "crippled" because it has a burden voltage of 10mV/mA instead of 1mV/mA. etc.
Usually, with meters, a lower spec is done to meet a lower price point. But in the case in question it is done for the purpose of meeting a (niche) market need. A tool is not crippled just because it doesn't meet YOUR job spec.
Dave.
"David L. Jones" wrote in news:9f33ec2f-7412-4832-bcb5- snipped-for-privacy@b38g2000prf.googlegroups.com:
Makes sense but do you concede that understanding the conditions matters more than the meter? What matters in wiring that is capacitatively or inductively coupled but not directly so, is that some kind of light load is placed on the line, and the voltage measured across that load. Only when that load needs to be a simple resistance can it be assumed that it is the meter's job to include it. In all other cases it can be assumed that the meter should tax the circuit as lightly as possible while analysing an external load chosen to fit the analysis needed. Which in turn directly implies that in the hands of someone who knows electricity, especially AC and frequency dependent behaviour, the high impedance meter is the way to go. Ideally with a plug-in load module or two, just as meters used to come with plug-in current shunts.
I don't test for live circuits with a DMM. I use test lamps or a low(er) impedance voltmeter. If you worked for me I would sack your arse if I caught you using a DMM to test for live.
Who said anything about it being *analogue* ?
Impedance is a property of the input of the meter not the display type.
I've used high and low impedance analogue meters and the same in digital form.
No, you carry the correct tools. You use a load to test for live/dead circuits, not a DMM. (I use test lamps with fuse protected leads). If you need to measure voltage, then you use a voltmeter...how hard is that to understand????
On Thu, Jan 22, 2009, 7:51pm snipped-for-privacy@gmail.com (Arlowe) wrote: krw explained on 21/01/2009 : On Tue, 20 Jan 2009 22:05:27 -0300, YD wrote: Late at night, by candle light, Arlowe penned this immortal opus: krw used his keyboard to write : In article , snipped-for-privacy@gmail.com says...> krw explained on 19/01/2009 : On Sun, 18 Jan 2009 19:35:00 +1100, Arlowe wrote: on 16/01/2009, Paul supposed : On Jan 15, 2:19=A0pm, "David L. Jones" wrote: "Paul" wrote in message news: snipped-for-privacy@x8g2000yqk.googlegroups.com... I'm testing a new DMM I purchased, AM-240 by Amprobe. It claims *over*
100Mohm impedance in 400.0mV mode. Nothing new there, many DMM's have selectable "high impedance" or "HI-Z" modes on the mV range. e.g. the Fluke 87. I've looked at the specs of ~ 30 DMM's today, include a lot of fluke's, and never seen anything near 14Gohms impedance. Keithley has an electrometer that's probably higher. Most DMM's are around 10Mohms (not gigaohms) input impedance. Don't you think 14 gigaohms is a bit high? PL The evil thing about Voltmeters with very high impedance is they will read induced voltages that analog meters wouldn't. It makes a voltmeter useless for checking for live circuits in a crowded panel. A craftsman never blames tools for his failures. Hackers, on the other hand... If you work with electricity you had better know the limitations of your tools or you will find them...the hard way. That is certainly true (though perhaps your heirs are the ones who will find you), but doesn't modify my statement. In this case, the tool *can* be used as long as the one using it knows what he's doing. Ok....everything seems to pass right over your head.... I pointed out a limitation of a DMM and you seem to be inferring that I am somehow a hack who blames his tools... BTW> I am not a "craftsman" I am an electrcian.. You don't do what I do for as many years as I have without knowing what the f*ck you are doing. What's wrong with using a hi Z voltmeter in a live panel? I do it more often than I really care for, and never have a problem. There isn't anything wrong with it. Analog meters are dead. High impedance digital meters are only a problem if there is a loose nut inside the panel, holding the leads. I don't test for live circuits with a DMM. I use test lamps or a low(er) impedance voltmeter. If you worked for me I would sack your arse if I caught you using a DMM to test for live.=3D>Arlowe: Ye shouldest cover thine arse and prepareth for a loss if mine=
DMM, openend Ammeter would causeth thee to derecruit me., there is no law or work code regulation violated by testing a live circuit with the proper test equipment and procedure...some DMMs' come with a clip on carrying case to facilitate it being attached to chassis bodies etc. for hands free testing.I wouldnst' work for thee anyway, Troll.
The Mighty WontVolt
Re: Freaky Amazing DMM?! Group: alt.engineering.electrical Date: Thu, Jan 22, 2009, 8:01pm (EST+16) From: snipped-for-privacy@gmail.com (Arlowe) After serious thinking krw wrote : In article , snipped-for-privacy@gmail.com says...> On Jan 21, 8:17=A0am, Paul wrote: On Jan 21, 7:34=A0am, Stuart wrote: In article , =A0 =A0krw wrote: Totally useless in areas of high RF. Wrong. That statement simply exposes another large hole in your knowledge and experience. I spent 20 years on a high power HF transmitting station - believe me - I *know* As the man says, the proper tool for the job I would agree. Take two meters. One is 1Kohms. The other is 1Gohms. If the load is low impedance, say 100 ohms, then there's an appreciable error with the low impedance meter-- simple ohms law. While the error associate with the high impedance meter is unmeasurable. People are probably confusing the fact that a high impedance meter while unconnected to anything will pick up signals, for obvious reasons. Paul Sorry, I didn't pay much attention who I was replying to. I'm not taking sides, but I am saying that high impedance meters are better. Right. It's easy to lower the effective impedance of a high impedance meter. Going the other way is a lot harder. No, you carry the correct tools. You use a load to test for live/dead circuits, not a DMM. (I use test lamps with fuse protected leads). If you need to measure voltage, then you use a voltmeter...how hard is that to understand????
=3D> Goeth ahead then, it is thine arse..Ye can goeth about testing with breakable bulbs [I keepeth them only for quick droplighting]
Whilest others [yon servant included] testeth circuits with one shot deal precision measuring instruments thou canst looketh like a fairytale lightning bug all thou wantest};{)
The Mighty WontVolt
The Mighty WontVolt formulated on Thursday :
I can read headers...you are Roy...Roy the wannbe. I have seen you around... nobody seems to like you. I understand why.
You don't even know what test lamps are ... I'll explain.. in small words, just for you.
2 incandecent lamps, usually 240 volt 20 watt edison screw lamps connected in series, connected to a pair of fuse protected test leads. I'll even give you pictures:'effing nutter..
krw used his keyboard to write :
I didn't say you had to use an analog meter. I said that they do not have the same problem. An analog meter "IS A LOAD" a DMM is NOT.
No shit... exactly my point. A voltmeter with a high impedance is not the tool to use to test for live circuits....
Sparky, carry crap tools? Ok, you don't need much and evidently=20 can't handle a good tool.
It is exactly the right term. It is a high impedance meter that has a shunt added to cripple it's input impedance.
If it was a .1% meter with the .5% feature added, yes, it was "crippled".
It does one thing and one thing only. The uncrippled meter will work in a wider variety of circumstances, though we are getting pretty far from the original point.
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