From: Paul
Date: Tue, 26 Dec 2000 21:41:38 +0000
Subject: Re: [TSSP] early idle testing
Marc, I think I'm getting the right picture from your description. A few comments at random... Use a sine wave from the generator, not a square. The extra harmonics in the square wave will confuse the picture. I'm glad you're picking up the proximity effects, you'll soon get an idea of how much room the coil needs. The counter connected to the top won't help at all, and it will hamper the scope readings, which are the ones you really want. If you send in a sine wave, you'll get a sine out, of the same frequency - there's nothing in the TC that can alter the frequency so there's no need to count the frequency coming out. Continue as you are, but with sine into base, scope connected to top, and sweep the generator through its frequency range. You'll know when you hit a resonance - the voltage seen on the scope trace will shoot up. Practice finding the resonances like this, and then repeat but this time without the scope connected to the top of the coil. Instead, feed the scope from a little search coil, the signal will be vastly smaller but, relieved of the burden of the scope connection to its top, the coil will approach its proper resonant frequencies. See if you can indentify the lowest three resonances, and tell me how high off the ground the base of your coil is. The complicated stuff you're seeing on the scope, with various different frequencies is the result of putting a square wave in. Each edge of the 45kHz square will set the coil ringing at 200kHz or so. This doesn't help at all, so stick to sine waves. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.