Re: Magnetic quenching.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

 >
 > With only a voltmeter and resistor I would expect that you would get
wattage
 > readings only when the load is not reactive. If the load has reactive
 > components you would get VA or the same information as when using a
 > voltmeter and ammeter. To find wattage with a reactive load you need a
 > wattmeter. I use a wattmeter, voltmeter and ammeter so I can find the
watts,
 > VA, reactive power and the power factor. There has been some talk about
 > using electronic meters but they probably would not last very long in the
TC
 > environment.

With an AC voltmeter, a series resistor and a series capacitor or inductor,
you can measure true power, apparent power, vars, watts, power factor etc.
It's called the "three meter technique" when measuring RF impedances.
Requires a bit of math, but these days, that's no big deal.  You want a
capacitor or inductor that has a reactance that's not too huge compared to
the load, but also not so small that there's a lot of measurement error.
(X=1/(377 * C) (in 60 Hz lands).... Say you're looking at 1 kW loads on 120V
(i.e about 0.1 ohm).. you want a reactance that's probably in the area of
0.01 ohm.  That would be a HUGE capacitor (1/3 Farad!), so, an inductor is
probably a better bet.  (X=377*L)  1mH=.377 ohm, 10 uH = .0038 ohm, which is
in the right ball park.

Electronic meters should work just fine, if properly used, in a TC
environment.  Granted, if it takes a streamer strike, it's going to die, but
for just measuring AC line stuff, should be no problem.

 >
 > Dave - I have never seen a digital wattmeter. I would be interested in
 > hearing how they work with TCs. Standard analog wattmeters cost only about
 > $15. You can use current shunts for higher wattages.

The Kill-A-Watt (available in a wide variety of places for $30-50) works
quite nicely and gives active and reactive power, etc.
They're available in a 240V version (for EU and UK use) as well as a 120V
version. Up to 15-20 Amps, as I recall.