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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The Radar Kilovolter is a spark-gap voltmeter that has nothing to do with Radar, but Kilovolter would be quite approprate if spelled Kill-0-Volter.
I bought it on ebay for a pound, about NOK 9.
The rough re-cycled cardboard box has the texture of egg cartons, and tells us that it came from the post-war rationing era, the years of so-called 'National Austerity,' 1947, or 1948 perhaps. UK television broadcasts had stopped in 1939 for fear that the Germans would use the VHF signals to home in their bombers, and was not re-started until 1946. The service was again suspended in 1947 due to a national fuel crisis, so there were very few trained TV repair men, and very little specialist TV servicing equipment that technicians could afford. The Radar Kilovolter spark-gap voltmeter was launched into this impoverished market, and must have been responsible for numerous electric shocks.
As you can see, the knob on the end is first set to 30kV, the probe is then placed on the high voltage source, and the black wire is attached to the Earth. The knob is then turned, reducing the gap, until a spark jumps between the spheres, when the voltage is read off from the position of the cursor on the scale. The cursor runs along a rail and is moved by a thin cord, in the manner of the radio wavelength scales of the period.
The outer skin is made from thin, bendy celluloid, and turning the knob while holding the probe tip on the high voltage source must have been memorable experience...
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Actually pretty accurate if enclosed and containing controlled atmosphere.
the sphere trick is a well known method of determining spark length, and if atmospheric pressure and temperature is known (assume humidity is zero if using silica gel in air path) is pretty good.
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
Proud Mary wrote ...
The outer skin is made from thin, bendy celluloid, and turning the knob while holding the probe tip on the high voltage source must have been memorable experience...
That's hilarious! Surely responsible for many bites, I wonder what serious market penetration it ever had...
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The Radar Kilovolter - a dangerous contraption
