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RE>My new O-scope and Secon
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From: Dale Hall [SMTP:Dale.Hall-at-trw-dot-com]
Sent: Thursday, April 16, 1998 5:43 PM
To: Tesla List
Subject: RE>My new O-scope and Secon
RE>My new O-scope and Secondary
Hi Erik & all,
Measuring DC voltages is easy using a voltage divider to the scope.
Take into consideration the input R of the scope (50ohm,1/10 megohm or ??)
Measuring HF Pulse voltages is more complicated. The DC divider requires
compensation due to the reactance's of distributed capacitance of divider R's.
Faster rise and fall times = higher frequencies = lower reactance's paralleling
the resistance's and upsetting the divider ratio in a frequency selective manner.
Commercial x10 x100 x1000 scope probes are constructed with compensation
adjustment. Anytime a new probe is used, it should be compensated with the
scope square wave calib output by adjusting for a Square result, otherwise
pulse measurement is relative, not calibrated.
Commercial probes are recommended but pulse probes can be constructed/calibrated.
Of significant importance is tesla primary current measurement. Commercial
active and passive current probes/amps are available that include a slide
open/close magnetic coupler, again recommended. Since it may be used on the
low side there is less risk of destructive coupling into the scope, which must
always be carefully accounted for, if the scope is valued !
A torrid core may be placed over the low pri side = 1 turn with a winding to
the scope taking into consideration the turns ratio and scope input loading to
make a current monitor. (at Hi currents 1:1 may be enough depending on
the input range of the scope, but is typically 1:10 or 1:100)
Dale
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Date: 4/15/98 9:05 PM
To: Dale Hall
From: Tesla List
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From: ESchulz531 [SMTP:ESchulz531-at-aol-dot-com]
Sent: Wednesday, April 15, 1998 9:26 PM
To: tesla-at-pupman-dot-com
Subject: My new O-scope and Secondary
All,
I just bought an oscilloscope and I was wondering how I could measure my
primary voltage with it, use lots of resistance? Any good ideas I could use
it for, as in for my tesla coil? I found out that my secondary resonates at
220 kHz, not the 660 kHz that I had though, so I guess it was at the third
harmonic. I was getting 18" sparks at 660khz using 900 VA, tomorrow I will
see what happens when I lower the frequency to 220khz by using my new large
primary.
Thanks,
Erik