From: Paul
Date: Tue, 02 Jan 2001 10:46:10 +0000
Subject: Re: [TSSP] NSVPI - Terminated Coil Results
Terry, All,
You might like to try the following modification to the NSVPI
gradient probe, in attempt to get it to work without requiring
electrical contact with the coil. The idea is to add in an RF
choke to provide a DC path for the diode to charge the storage
cap.
| pt
| ----||--- <-------------[diode]--
| pc | |
| | |
sec | -[choke]- --- storage cap
coil | | ---
| pt | |
| ----||--- <----------------------
| pc
|
'pc' are the 'contact capacitances' of the two probe terminals 'pt',
[choke] is an RF choke wound on a miniature toroidal ferrite
core - this so that inductive coupling with the secondary is
minimised. Alternatively, use a high value resistance instead, and
allow time for the storage cap to charge.
We could do to figure out a way to make an absolute top volts
measurement. Terry's toroided coil Q of 164 gives a predicted
voltage gain of 168.5, but the cumulative gradients, with 0.12
diode drop added, gives around 155 volts, so we have a discrepancy
here which appears larger than either the measurement or prediction
errors.
Note that for the bare coil case, Q=60, Vgain predicted is 68.5
and the cumulative voltage was 69.72 - within limits.
Cheers,
--
Paul Nicholson,
Manchester, UK.
--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.