9 Apr
2005
9 Apr
'05
5:47 a.m.
On Fri, 8 Apr 2005, Tony Duell wrote:
I once helped a studnet doing a practical on an LC
series circuit. I
think he was looking at the phase relationship between the applied
sinusoidal voltage and the voltage across the capacitor. And he couldn't
get any sort of sane results. IIRC he saw almost no phase change at all.
He was using a standard (albeit cheap) modern double-trace 'scope, which
would have been quite capable of doing what he wanted. But he had one
control set wrongly. He got a trace, but it wasn't meaningful.
OK, what was he doing wrong. Some of you will get this instantly, I think...
If he was using a dual trace method of phase comparison... he probably
had the dual trace control set to "alternate" instead of "chopper",
so the trigger was responding to different signals, foiling up
any phase comparison.
Carlos E. Murillo-Sanchez email:
carlos_murillo at skipthistoemailme.ieee.org
Dean of Engineering, Universidad Autonoma de Manizales, Manizales, Colombia
----
"Western civilization... thought like the greeks, organized itself like
the romans and believed in itself like the hebrew." -- Ortega y Gasset.