From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Thursday, July 24, 1997 8:26 PM
Subject: Single Shot
Might just comment on the usefulness and limitations of this.
I use it to: (a) compare attached spark length with calculated
voltage output using a figure of around 30 - 35 kV/inch to a ground
rod. That figure of course is highly debatable but I have found it
tracks primary energy amazingly well. However, other's work in using
this suggest that this is too high a figure.
(b) check initial tune without hammering the primary
components to pieces
(c) testing for all manner of component adjustment
including k, once again with minimum risk to capacitors etc.
(d) testing capacitor quality
(e) setting static gap firing voltage with a reasonable
degree of accuracy if the power supply is metered
As a measure of how far a running coil will throw sparks under normal
repetitive conditions it is a complete no go. I submit that coil
efficiency is no different when using this test than repetitive
running (leaving transformer losses aside) and may well be better
since the transformer cannot influence gap dwell time.
An extremely useful demonstration using this technique is to see
how different k's affect primary dissipation under different
secondary loading conditions. These effects are quite noticeable
under normal running conditions but using single shot allows one to
observe gap behaviour without running the risk of serious eye damage.
For this purpose, attached sparks present much the same impedance to
the coil single shot as they do repetitive. I would encourage people
to do this. A lot can be learned about basic coil behaviour by moving
a ground rod in from outside strike range to touching the terminal
and seeing what happens at both ends of the system at intermediate