From: "Terrell W. Fritz"
Date: Thu, 25 Jan 2001 21:49:37 -0700
Subject: Re: [TSSP] Top voltage testing
To follow up... The generator still seems to work well (but I need that HP arb anyway :-)). I disconnected the coil and the current fell to 3.4uArms. I disconnected the shunt resitor for the generator and got 5.3uArms. So the shunt C and noise seem to be insignificant. I also tried holding the wires and such but the current held steady. Cheers, Terry snip... > >You mention the 1 ohm resistor is right at the generator output. >The current reading will therefore include current shunted to ground >through the feedline capacitance and thus never reaching the coil, >which will make the reading artificially high. The coil input >impedance is around 600 ohms, and the feedline C necessary to raise >the current by 5% is around 120pF, which corresponds to 3m of coax. >Perhaps you can move the current shunt to the coil end of the >feedline? > >Also, if the conducting loop formed by the 1 ohm current shunt, >the HP probe leads, and the HP meter, is picking up an EMF induced >from the coil B-field, this would add a component (leading or trailing >by 90 deg, depending on loop orientation) to the voltage developed >across the shunt resistor, and the RMS readings from the HP would be >artificially high. Do you get a lower current reading when the HP >probe leads are twisted together? > >Any instability in these two possible factors might also account for >the variability of the Qi readings. > >Perhaps you could have a closer look at the current readings and see >if Zft can be brought into line. > >Cheers, >-- >Paul Nicholson, >Manchester, UK. >--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.