From: Paul
Date: Tue, 16 Jan 2001 11:49:01 +0000
Subject: Re: [TSSP] Top voltage testing
I'm allowing for the probe by the simple expedient of adding an extra lumped top capacitance and increasing the loss factor. These fiddles are adjusted to obtained the measured f1 and Q. This means that I'm ignoring the probe's effect on the coil field and assuming it impinges only on the topload. Seems to be doing OK, might be poorer on a smaller coil. The approximation should be reasonable if the probe approaches the coil from above. I'm looking forward to getting similar measurements from other coils, which will be a lot easier if satisfactory allowances for a regular scope probe can be made. Terry's coil is tricky in this respect since the Q varies rapidly with Fres due to the sonotube loss. Could do with some measurements from an intrinsically low loss coil. Terry, thanks for the further voltage readings. Interesting note about the difference between the Q derived from Vtop and that from Ibase - it suggests the ratio Vtop/Ibase (ie the transimpedance) is not constant - I assume Vbase remained constant as you looked for the 71% Ibase points. I'll respond with another post later on - have to do some paid work for a few hours first - but I'll set a computer to generate a plot of Vtop/Ibase as a function of frequency in the region around f1. I've just assumed it's a constant up to now. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.