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Re: Measuring static gap BPS

Hi Gary,

	I have not actually done this but this is how I would do try it.

I would be VERY worried about killing the sensitive counter with high
voltage!  Counter inputs or not very tough and the designers don't expect
people to be doing stuff like were are.  Scope designers know that someone
out there is going to hook the scope up to a Tesla coil and they do all
they can to make the scope survive.  But counter designers are far less
weary of what the device my get feed.

I would place a resistor in parallel with an LED, a regular incandescent
lamp, or a neon bulb in series with the ground wire of the secondary.  This
will make a flash of light when current flowed.  I would then pick that
light up with fiber optic cable and go to a fiber optic sensor to the
counter (may need low pass filter).  That would provide very good high
voltage isolation and give a pulse at each secondary pulse.  Perhaps
picking the light up right at the gap would work too with long fiber cable.

A current loop on the secondary ground may give a nice signal but the lead
wire to it can get nasty spikes from all the local RF fields.  I would
definitely get some long fiber optic cables for this.  Any wiring going
near the coil is going to get "hot" enough to kill the "not well protected"
input of a frequency counter.

Another "easy way" may be to set up any tape recorder to record the sound
from the coil.  Then play the tape of the sound into the sound card in your
computer and use those funny programs to "view" the signal.  You should be
able to count the pulses just like a digital scope capture.  Even A
microphone into a counter with perhaps a little low pass filtering may do
the trick.

A plane wave antenna with a low pass filter may also work but they may be
too technical for this "should be easy" task..

I have never tried any of these "arm chair" ideas but, above all, don't
blow up the counter!!  Sounds like you have some fun experiment ahead!  let
us know what finally works...

Personally, I would catch the waveform off my plane wave antenna (peak
function) and have the digital scope's math functions tell me the frequency
or push the button and have it print the thing on the printer.  But I have
"toys" most coiler's can only dream of ;-)))

Cheers,

	Terry


At 09:02 AM 12/22/1999 -0500, you wrote:
>Has anyone found an easy way to measure the firing rate of a static gap?
>I'm sure there's a way to devise some sort of optical or inductive pickup
>with a low-pass filter and limiter, and feed this into a frequency counter.
>But rather than re-invent the wheel, I thought I'd ask if someone else has
>done this.
>
>Regards, Gary Lau
>Waltham, MA USA
>