Re: More Mini Coils (scopes)
From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: Friday, June 27, 1997 3:42 AM
To: Tesla List
Subject: Re: More Mini Coils (scopes)
At 08:15 PM 6/26/97 +0000, you wrote:
>Sent: Thursday, June 26, 1997 4:54 AM
>Subject: Re: More Mini Coils (scopes)
>In a message dated 97-06-26 00:13:05 EDT, you write:
><<snip> Note that measuring the wattage obtained at the input to the TC
>>power transformer and the maximum spark length obtained from the coil
>>is not of much value. This is because there is no way to find the wattage
>>that produced the maximum spark length. It is interesting to note that this
>>type of rating for Tesla coils has been used for years. The assumption
>>was that the wattage was the same for all sparks. This is obviously not
>>correct because if it was all sparks would be the same length for a
>> certain coil.
> > John Couture
>You're looking at "true" efficiency; energy in vs. energy out, per spark.
>And from this point of view you are correct. I prefer to look at Tesla
>coils from a "practical coiler's" viewpoint in this sense: Suppose one
>coil drew 1000 watts and gave 50" sparks that were all equal in length.
>Now suppose another coil drew the same 1000 watts, but gave some
>sparks that were only 40" in length, but sometimes gave sparks that
>were 60" in length. It could happen that the true efficiency of both coils
>could be equal (depending on the percentage of time that 40" sparks
>were given and the percentage of time that 60" sparks were given. )
>Yet, IMO, most coilers would probably "enjoy" the coil that gave
>occasional 60" sparks...more. And most coilers would probably
>consider the coil which gave 60" sparks to be more efficient, although
>as you correctly point out, it may not be. One could argue, and say,
>that taken to the extreme, a coil could be built that produces 40"
>sparks, and running continuously, would throw out a 60" spark only
>once every hour...would such a coil be considered to be efficient?
>IMO...NO, because it would not "look" efficient.
>I think that the use of two different definitions for spark length
>efficiency are useful; the "true" energy in...energy out definition, and
>also the practical coilers definition.
>Just my viewpoint,
In your example above the efficiency may be equal but probably would not
be equal. If it was equal there is no way to find out why the two conditions
produced equal results. I prefer to use methods that can be more specific as
I know it is a temptation to use the longest spark for rating the coil. In
fact it appears to be unfair to the builder not to use the longest spark.
But the truth remains it is not possible to know exactly what made that
extra long spark possible so it may not be possible to duplicate the setup
by other coilers. A better way to rate a coil is to use methods that can be
duplicated by others.
I agree that energy in vs energy out is the scientific way to rate and
compare coils. Lets agree on the details for measuring the energy in and
energy out so all coils are rated by the same methods. This means when coils
are compared the comparison is on a resonable scientific basis. By
scientific basis I mean that when the coil is duplicated by some other
coiler the outputs will be the same and not different because of some
unknown conditions that existed for one coiler. The unknown conditions would
include things like the exact way the imput vs output was determined.
> For example, energy includes a time period. So the energy out cannot be
one spark but many sparks that are averaged over time. However, the energy
in is a more complicated matter.
The energy in can be found in several ways, but the method used must be
simple enough that every coiler will use it. That leaves out complex
electronic circuits that would be difficult to use and understand for the
Finding a simple method to measure the energy input of a Tesla coil is not
easy. At present coilers are using a voltmeter with ammeter or a wattmeter
which do not register the true conditions. It is well known that the amperes
are in surges regardless of the type of power source, AC or DC. The simplest
way to measure this type of current is with an electric lamp. Hot wire
meters, coulometers, etc., are out because they are not available to most
The electric lamp meter gives true RMS current values when properly
calibrated and is not sensitive to frequency like RF meters and similar
meters. The calibration of the lamp meter is not difficult. With a voltmeter
and a calibrated lamp current meter the true energy TC input can be
determined. With this setup the power factor can be ignored. A true energy
input vs average spark output rating can then be found for the coil.
Do any coilers have a better method to measure the TC input and output energy?
All comments are welcomed.