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Re: [TCML] Re: Dummy load for optimum cap size Experimentation



I'm making slow but steady progress in my experiment to determine the best
cap size based on using a halogen lamp dummy in place of a primary, and
monotoring the light intensity to indicate how much power is being
processed.

I'm recording the power at 120V and at full Variac setting.  The full Variac
setting is typically ~135V under load.  It changes slightly depending on the
cap value, but it is what it is.  When I set the Variac to get 120V, I
monitored the voltage with both a Wavetec 27XT DMM, and an old lab-quality
Weston analog meter, calibrated at the 120V point with the 27XT, with 120V
from the Variac, under no load.

But when the Variac is under load from the NST, there can be a significant
difference between the two meters (113V vs. 120V).  I'm speculating that
this is due to the loaded Variac output waveform being distorted, and the
two meters see this differently.

I don't own a true-RMS meter, so I have to decide which of these two
readings to believe.  I have been using the analog meter.  Can anyone
suggest which one might be closer to a true-RMS value?

Thanks, Gary Lau
MA, USA
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