RE: The PING Test

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

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


Paul -

With reference to your equation

Efficiency = 100% times(Q_unloaded - Q_loaded)/Q_unloaded

How would you set up the Second Ping test to find the loaded Q factor?
Assume we are looking only for the energy in the secondary (useful load) and
ignore the streamer loading.

In the Lamp Test using the pickup coil the lamp does absorb a certain amount
of energy from the secondary. This amount of energy can be measured and used
to estimate the energy in the secondary and determine the overall
efficiency. I agree the estimate is a wild card.

What method do you recommend to measure the energy in the secondary coil
ignoring the streamer loading? The streamer loading would be another
condition and would not have any effect on the charging of the secondary
circuit.

Monitoring the secondary base current can be done with an ammeter with
negligible energy absorption and gives a different value than the lamp test
above.

I agree some of these questions can only be answered in a general way. But
it does no harm to make estimates based on the information and tests we have
available. In this way we can make progress and make the necessary
corrections as we move along in the future.

John Couture

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, September 25, 2002 4:22 PM
To: tesla-at-pupman-dot-com
Subject: Re: The PING Test


Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<paul-at-abelian.demon.co.uk>

John Couture wrote:
> It does make sense and I showed in my post how any coiler
> can make the test and do the calcs.

John's ringdown test if fine, as an indicator of Q.  Many of us
use it.  By giving you the secondary Q, you thereby have the
energy storage efficiency of the secondary.  But it says nothing
about the system efficiency or output voltage, except in base-
driven CW mode, in which case Vtop/Vbase = Q applies (approximately).

In any system CW or impulsed, any definition of efficiency boils
down to asking what fraction of that initial energy ends up in
the useful load (whatever you define that to be).

Therefore, in order to determine the fraction of energy leakage
which is defined as 'useful', you must take *two* Q measurements
(by ringdown, bandwidth, whatever you like) and compare them in
the usual way, ie

  Efficiency = 100% times (Q_unloaded - Q_loaded)/Q_unloaded.

Any formula claiming to show any sort of transfer efficiency
based on just a single Q value is a nonsense.  By definition, it
must evolve from the difference between the loaded and unloaded
behaviour of the system, regardless of what is considered to be
the 'loading' and what is considered to be the 'loss'.

The lamp tests that John has described in the past will at best
give the efficiency of coupling to the lamp.  As such, it might
be a useful setup aid, but no better in principle than simply
monitoring the secondary base current.

As regards John's question:
> Should the  secondary turns be increased or decreased to
> increase the secondary voltage and the spark length with
> the same H/D coil?

The glib answer is that it depends whether you've got too
many or too few turns to begin with.  The question needs to
be rephrased to make sense.  It should say: is there an optimum
number of turns for a secondary, given some constraints such
as a particular power supply, BPS, firing voltage etc, and
allowing Fres, Cpri, Lpri, k, turns, wiresize, all to be free
variables?  And if so, how do we calculate it?

We have all the pieces with which to answer that question, bar
two.  The least important of the two missing links is to
be able to calculate the Q factor of the primary and secondary
coils.   Much more serious is that we don't understand how the
secondary couples to streamer loading - the dynamics of the
coupling determine how well a particular impedance of secondary
will drive streamers from a given top terminal.  If we could
determine this, even just empirically, it would complete the
theoretical package necessary to answer the simple question:
"How many turns shall I put on the secondary?"

So John is asking a question that we can't answer at the moment.
--
Paul Nicholson
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