James Meyer wrote:

On Sat, 17 Apr 2004 07:43:49 GMT, Robert Baer posted
this:

John Larkin wrote:


Well, all the usual methods: resonance width, phase shift, ringdown,
stuff like that. I work with gadgets with Qs over 1e9, and people
measure them without difficulty.

John

Ringdown is the easist way when Qs are extremely high.

You must still account for the energy you extract from the circuit in
order to measure the ringdown. Even the energy needed to drive a high impedance
probe is significant when the Q gets high.

IOW, the Q without the probe will be higher than the Q when you insert
the probe to measure the Q.

Jim

Not a problem; use two different loads.
Just like measuring the internal resistance of a battery or a curent
meter...
...Never done directly.