RE: [Fwd: RE: TC Secondary Currents - was ( Experimental Help - Terry?)]

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Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


I agree that the non linear calibration test or the lamp matching test
doesn't work very well. As you say the non linear calibration is a dog
because of the difficulty in matching lamps.
The matching test creates a problem in finding lamps with equal non linear
characteristics. All of these problems are eliminated by using only one lamp
and a photo light meter to do the test.

This is the way I do the test. The lamp and light meter are in a light tight
box. The lamp is connected in series with the TC secondary ground wire. The
light level on the light meter is noted when the TC is operating. The lamp
is then connected to a DC source and ammeter. The voltage varied until the
light meter registers the same light level as the when connected to the TC
when it was operating. The DC current that you read will be the exact
AC(RMS) current as when the TC was operating. It is a good idea to repeat
this procedure several times and then average the current readings to find
the most accurate secondary current.

It is obvious that with this test the non linearity of the lamp is not a
consideration. Also the accuracy can be improved with multiple readings.
There is no need to calibrate the light meter or anything else in this test.
I used 12 volt automobile lamps but you may have to use various size lamps
or shunts to measure higher currents. Of course, this test does not tell you
whether the current is ohmic or reactive or "displacement" which is the
problem.

John Couture

-------------------------



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, March 01, 2002 9:09 PM
To: tesla-at-pupman-dot-com
Subject: [Fwd: RE: TC Secondary Currents - was ( Experimental Help -
Terry?)]


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



>Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" ><couturejh-at-mgte-dot-com>

>I agree the incandescent lamp is an excelent way to measure the TC
>secondary current. The test is easy and accurate enough for coiler's
>use. Contrary to what some coilers have said the non linearity of the
>lamp is not a consideration if the test is done properly.

	As i said, the nonlinearity is 'covered; in the calibration.
	It occurs to me that this technique will be insensitive at low
	currents, (the bulb is dark...).  'low' will depend on the
	'size' of the bulb.

> The brightness of the lamp is exactly the same for both AC(RMS) and DC.
> The lamp has the advantage that with AC the frequency and waveform do
> not affect the measurement.

>I have done this test many times and often wondered just exactly what
>kind of current I was measuring.

	hmmmm?
	'current is current'.

	Over simplifying by using the transformer 'model' its the
	secondary current.  the magnitude varies with:
		breakout or nor
		Corona or no
		Magnitude of radiated field.
		Secondary in or out of resonance.

> Was the current a reactive current charging the toroid and self
> capacitance of the coil or was it an ohmic current that was
> producing corona and the streamers? And how about the Maxwell
> displacement currents?

	I suggest that, as it all flows thru the one point it is
	the sum of all.  The nature of the variation of current
	with operating conditions means one or another may dominate
	at various conditions...

(To save a post)
Someone suggested using two lamps, simultaneously matching the
brilliance of a DC, metered lamp with that of a 'sense' lamp,
then reading the current from the 'DC' lamp.  Seems admirable,
with the caveat that the lamps may not match exactly:  wiring
so that the two lamps could be switch from on 'role' to the other
would allow interchange, to take readings from either...

One might epoxy on a photocells (matched?) to allow better
matching of the two bulbs brightness.

(all of which is getting kind of elaborate...   8)>>)

best
	dwp