Measurements using field probe

From:  terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
Sent:  Monday, June 29, 1998 12:46 PM
To:  Tesla List
Subject:  Re: Measurements using field probe

Hi John,
        The experiments were done by Bert, not me.  Many of the original
numbers were pulled out of the air to show the I^2R problem.  Bert has since
posted a much better analysis of his coil measurements that are probably
very close the truth.  The new numbers are much closer to what we would expect.
        Bert's note that his halogen light bulb varies in resistance by a
factor of ten raises some concerns about the accuracy of this type of test.
A good calorimetric meter would be better but I am not sure it would
survive.  They are very expensive!!  The fact that Bert is getting such good
values is due his very good understanding of what his measurement setup is
doing.  It should be noted that we need to consider that these measurements
need to be done at perhaps 50MHz signal levels so there are many high
frequency things that also need to be considered.  Obviously, my antenna
system vastly simplifies all this but experiments like Bert's provide the
very important "second opinion".

        Many my not realize just how far we have come in efficiency
measurements in the last month.  We can now measure energies and losses in
output arcs in real time to fair accuracy!  Some of the crosschecks on
accuracy suggest only a few percent error!  Unfortunately, the output is not
a simple resistor but is deeply involved in dynamic electrostatic field
behavior.  Still very manageable, but not easy.  When Q and resonant rise
were removed from the list of factors, many of the theoretical
considerations were vastly simplified.  We now pretty much know were all the
power is going except in two areas.  The spark gap and the secondary arcs.
Many tests are showing that the energy lost in a well-constructed spark gap
is fairly low.  Probably not a major concern.  The quenching and good RF
design are very important but once that is done the gap does a good job at
not loosing much power.  Hopefully, I will be able to get the fiber probe to
give better current measurements now that I understand the saturation
problem.  In many ways the output arcs are very similar to the gap arcs.  It
appears that good RF design is also important here as well.  I suspect that
a large, smooth, highly conductive top terminal will perform much better
than the opposite.  I have not sat down and gone through all the
efficiencies for my coil, but I suspect well made coils are very efficient
in that they are not wasting heat.  Much more can be done to translate the
energy into sparks, however.  

        Terry Fritz

At 11:23 PM 6/28/98 -0500, you wrote:
>From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
>Sent:  Sunday, June 28, 1998 7:42 PM
>To:  Tesla List
>Subject:  Re: Measurements using field probe
>  Terry, All -
>  Congratulations on your "light bulb tests" experiments. Your tests are
>very important to me and all the other coilers. The lamp meter is an
>excellent method of measuring currents in an operating TC.  The TC RF
>currents in the secondary are random pulses at high frequency. Ordinary
>meters cannot accurately measure these currents. Even hot wire and
>colometric meters have limited use because they are calibrated for only
>special conditions.
>  Using a variety of lamps and suitable shunts and properly calibrated you
>can measure TC currents for any condition. I made many of these tests
>several years ago on some of my small coils as I show in my Tesla Coil
>Construction Guide. Note that the lamp gives an RMS output instead of an
>average output. Average is 63.7% of peak while RMS is 70.7% of peak. The
>lamp output is non linear and limited but that can be taken care of by using
>several different lamps  with appropiate shunts.
>  I not only measured the TC secondary currents but also was able to find
>the overall efficiency of some of my coils. This is also shown in the Guide.
>The efficiency was found to agree closely with the TC efficiency graph (Fig
>7) I shown in the TC Notebook. As I have not found any coilers who have
>duplicated the overall efficiency tests I have not been able to verify my
>results. Hopefully more coilers like you will help me make verification
>  It is interesting to compare your estimate of 950 KV (at 100% eff) in the
>secondary with the 462 KV in the JHCTES program. This gives a secondary
>voltage efficiency of
>  (462/950) x 100 = 48.6 percent for sec cir, not overall.  
>  The program shows 8.6 Inst peak amps in the secondary circuit. This gives
>  462 x 8.6/1000 = 3.97 Inst megawatts in the secondary.
>  I have not been able to verify your 31.62 amps. Could this current be 
>  8.6/.486 = 17.69 amps??   and
>  sqrt(313) = 17.69?
>  For your toroid and coulomb calcs giving 47.43 uCoul.
>  The JHCTES program gives for   Q = C x V
>  (50^-12) x (462000) = 23.1 uCoul   and
>  (23.1 / 47.43) x 100 = 48.7 percent as above
>  The sec voltages, uCoul, and eff seem to work but not the sec currents. 
>  Some experiments appear to agree with calcs but we have a long way to go.
>We need more coilers to build, test, and do the calcs with more coils to
>verify the above results. This can be done with small coils and does not
>require big sparks!!  
>  John Couture