:) Are you unfamiliar with how multimeters can kill people?
NT
:) Are you unfamiliar with how multimeters can kill people?
NT
All too familiar which is why I won't use one on mains. ;-) There are far better designed devices designed specifically for this job.
Last week I picked up a used but in perfect condition high voltage probe made by AVO. When used in conjunction with my good 'ol British AVO
***ANALOGUE*** meter, I can now measure voltages of up to 32kV. :) Try doing that with one of your BnQ ten quid specials. :)
Pretty useless for measuring things like CRT HT, though. Input impedance is too low. A similar probe on a 2 quid DVM will be fine. ;-)
that's easy. string of 3w resistors, bit of coathanger, bit of polystyrene. BTDT.
NT
3 watt resistors?? Hmmmm.....And what grade of polystyrene would that be? I'm sure you know exactly what you're doing, though. ;)
Yup, theyre long enough to have a useful voltage rating
any grade, its not specced for electrical insulation
I included a ground shield in the styrene so that if it fails for any reason it arcs to ground, not to the user. And naturally HV kit needs testing before use.
NT
Yeah, go pick on something that has like microscopic source impedance why don'tcha? Please note: I still keep a couple of DVMs and the really important thing is the ***PROBE*** - and having the balls to use it at 32kV (which TBH I must admit I don't have). But it is *well* out of DIY range, let's face it.
Ahh. I see. Makes sense in a 'get-you-home' sort of way.
No kidding? :-D
I'm sure readers will be reassured to know it only starts fires rather than electrocutes the homeowner.
Just discovered another meter in my possession (a Taylor Instruments) dating back to around 1960 that has a *basic* 2.5kV measurement capability at 20kopv, giving me the capability to measure EMFs up to 75kV if I can obtain an even higher rated 30x EHT probe - yeah, baby, yeah!
At one time measuring CRT HT would have been DIY for those who fixed or built tellies. I had a Heathkit valve voltmeter (with HT probe) for that job. Still got it. But it doesn't get used these days - any more than the AVO 8. ;-)
Is there anything that most all of us would need to measure up there at that voltage, seeing that CRT's are almost extinct now?...
No, it makes sense in a basic electrical engineering kinda way. Long resistors tend to have higher voltage specs.
nope
why would it start a fire? You seem to be missing the basic engineering behind this completely.
upto anything at all if it has enough current delivery. 20 k per v is too often too low of course.
NT
There never was, for most people. For electronic folk there's still microwave ovens, occasional HV power transmission, vintage tv, and other occasional/extreme projects. DIY x-rays anyone?
NT
Looking on YT I see quite a lot of nuts who are into indoor lightning. If you want to mess around with tesla coils and Cockroft-Walton multipliers,
32kV is nowhere near enough!
Sorry, I meant *huge* Zs, not "microscopic" - D'oh!
Yep, but do you measure those sort of voltages perhaps you know that a spark "x" of such a length is equal to "y" volts;?..
Do go on...?
Arc flash. Circuits after a CU's fuses don't deliver enough current for long enough to cause an explosion, further upstream they surely can.
NT
Yes, that's how a lot of these kind of measurements are carried out - in dry air of course.
Well you can't really blame me. Your description is a bit vague, after all: "string of 3w resistors, bit of coathanger, bit of polystyrene." "Engineering" seems rather a grand term for such a sloppy sounding lash- up. :)
It was the 'gold standard' 50 years ago when this meter was made! Anyhoo, as I said I keep a couple of modern DVMs with much higher input impedances so if lack of grunt on the part of the DUT is a problem I can just use one of them.
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