From: "Malcolm Watts"
Date: Tue, 16 Jan 2001 14:29:35 +1300
Subject: Re: [TSSP] Top voltage testing
Hi Terry,
The 10 MOhms is the problem. It will be hitting the Q
measurement for sure. Suppose Zo is about 30k. Then matching
impedances are about 40k for each end. Zo^2 = 9e^8. Suppose you
terminate one end of the coil with 100 Ohms. The other end will have
an equivalent shunt Z approaching 9 MOhms and the problem just gets
worse as the termination value goes down. This is typical 1/4 wave
line stuff and makes measurements a nightmare. No problem if the line
is RG58 etc. In fact, this is probably what made some of the Corum's
coils look so bad (e.g. Q of 60 for a large spacewound coil which I
reckon should have been at least 300).
Regards,
malcolm
> The probe bothers me too but Paul seems to think it works. The probe
> is 10.0Meg ohm 16.6pF. Also, the wire to the probe must really make
> some wild bends and disturbances in the fields around the coil. I
> think Paul accounts for this in his computer model but I don't
> understand it all well enough to know how. I don't quite see how I
> would calculate this but let me know what to do and I'll do it.
>
> Cheers,
>
> Terry
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.