# Re: In vs. Out

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From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Wednesday, July 23, 1997 2:31 PM
To: 	Tesla List
Subject: 	Re: In vs. Out

At 08:37 AM 7/23/97 +0000, you wrote:
>
>From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: 	Tuesday, July 22, 1997 11:12 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Re: In vs. Out
>
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John F. et al.

Malcolm's work on controlled sparks vs the variable single free air sparks
points out the situation that I have been talking about. The controlled
spark length and the free air spark length are not the same and must be
handled differently in tests. However, it should be noted that the
controlled spark will give you a true representation of the true average
energy output of the TC while the free air spark must use DC tests.
Dividing the average energy output by the average energy input will give you
the true efficiency of the Tesla coil.

If you want to use the single free air spark use a DC Tesla coil and
charge the TC primary capacitor once, then short the operating gap once to
obtain one free air spark from the secondary terminal. By doing this you can
actually measure the voltage on the pri cap. As you will know the
capacitance you can find the exact amount of energy input for that one free
air spark. This is not artistic, this is an engineering approach.

The true efficiency of the TC can then be calculated PROVIDED you know how
to convert the spark output to an energy output. I have done this DC test
and found it will give you a shorter spark and a lower efficiency compared
to continuous TC operation. This is because the ionization of the air from
previous sparks is missing. The ionization of the air from previous sparks
is what gives longer sparks either in free air or continuous.

But you must realize that the ionization of the air requires energy that
comes from previous conditions. This energy input for a single free air
spark under continuous operation would be impossible to measure. However,
the energy for this ionization is averaged out when using continuous sparks
(controlled sparks).

As you can see the free air spark test with a DC Tesla coil can be used
but would give lower efficiencies compared to a continous operation test.
Continuous operation gives continuous energy input and a continuous energy
output which is necessary to find the Tesla coil efficiency.

Note that Malcolm did not say how he was going to convert the spark output
to energy output. This is necessary if the TC efficiencies are to be found.
As I have mentioned before I show how I found the energies and efficiencies
for one of my coils in the TCC Guide. Instead of sparks for the output I
used an incandescent lamp with a light meter. The lamp brightness was
calibrated in watts on the meter. This lamp setup works from DC to RF
frequencies so you can use DC for the calibration.

John Couture

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--------- snip

>John, All,
>
>I have a concern, that the controlled spark length will give a very
>misleading impression of our TC capabilities.  Malcolm's work, if
>I understand it correctly, suggests that two different coils which
>happen to give the same controlled spark lengths, may give very
>different free air spark length, or occasional to ground spark
>lengths.  If this is true, does this seem OK to you?  Do you
>consider the maximum spark length capabilities of a coil to be
>of purely artistic interest?  To me this goes way beyond artistic
>effect.  If one TC is able to reach out and touch something,
>(occasionally), and another one is not...then there is some kind
>of real, physical difference in these coils.  Just because this
>difference may be hard to measure doesn't mean IMO that it
>should be ignored by anyone; artist, craftsman, or scientist.
>Furthermore, I think that these "reaching out effects" have a
>whole lot to do with ion cloud effects, break rates, etc.  This is
>an area of coiling that has been incompletely analyzed.  Instead
>of using a method that ignores these effects, (if this is the case)
>I believe that we should be attempting to understand, and
>measure these effects.
>