Re: Digital vs Analog meters

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

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

Tesla list wrote:
 
> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
><youngs-at-konnections-dot-net>
 
> On my DC powered coil, I tried using a LCD panel meter, powered by 9 volt
> battery, with appropriate shunts to measure current out of my HVDC supply.
> I was hoping for more accuracy than the analog meter.  Current should be
> fairly steady as I am monitoring current into the final 6 MF filter cap, not
> the high pulse DC output from it.
 
> But it didn't work.  Meter registered overvoltage whenever the spark gap
> fired, but recovered OK.  I tried bypassing the meter with a cap to keep RF
> or pulses out of it, but it didn't help.  So its back to good 'ol tough
> analog panel meters.

	The RF fields, near in, are fierce.
 
> Anyone had any luck using digital meters to monitor TC voltages or currents?
> If so, how did you do it?

	This can be a real challenge.   Commonly takes Much More than a
	single cap.  A full faraday cage around the meter is a starting
	point.  Add ferrites, or inductors on any lead(s) entering the
	cage.  (the battery makes this simple:   keep the battery inside
	the cage: only the current lead(s) need be filtered.)

	EMI is not simply 'stopped' by the cap, but can radiate around
	it.

	Basically, if an analog meter will do the job, it may be the
	simplest solution.

	best
	dwp