Metering

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

Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davep-at-quik-dot-com>

> Sorry to pick nits, but a recent reference to RMS power set me off, rather
> like fingernails on a slate blackboard.  Our meters measure measure average
> voltage and current on the dc ranges, rms voltage and current on the ac
> ranges,

	Indeed, care is in order here.

	Some do.
	The common ones do, the classic d'Arsonval/moving coil meters
	are, inherently, milliameters, that respond to the average
	of the waveform presented.
	(so long as it is within their frequency limit, which is small.)
	(If the waveform is symmetrical AC they will not respond, or
	respond with vibration: the time average of such AC is zero...)

	Some of the 'true AC' meters (Moving vane, moving iron, dynamometer,
	hot wire, thermocouple) are true RMS (Same caveat on frequency).

	The common moving coil meter calibrated in 'RMS' is ASSUMING a neat
	sine input.  (for which others have posted the conversion).
	Tesla Coil work involves relatively few neat sine waves.

> but only AVERAGE power (never RMS power).

	_power_ meters are relatively uncommon (i own a couple, as
	curios).  A typical 

	(
	I've a two volume set of books, about 2.5" thick, that gets
	into ALL the details of meters.  I've not mastered them, I
	mention them to show that there is a lot to metering...)

	best
	dwp