Re: [Phys-l] glassware needed

[Brian Whatcott <betwys1@sbcglobal.net>]

I have a lamp controller hooked to the halogen lamp standard by my desk.
I turned the light well down to a round current reading, and read the
following parameters from the inexpensive "Kill-a-watt 4400"
 meter (Cheesy name! <$20)

Volts 122.4V
Amps  2.00 A
watts: 158W
va:  245 voltamps
Fx: 59.9 Hz
p.f. 0.64

Turned high, I read:
Volts: 122.2V
Amps: 2.48A
watts: 293W
va:  303 va
Fx:  59.9 Hz
p.f. 0.96

These look plausible  for a microprocessor with an A/D that samples 
reasonably fast.
Hmmm....how would I check, without a calibrated wattmeter to hand?
Oh, I know: warm a fluid sample at high pf and another at low pf and check
 if the delta t is proportional to indicated power input?  :-)

Brian W

At 04:29 PM 1/1/2009, you wrote:
> Make sure that the 'inexpensive' watt-meter can correctly handle non-
> sinusoidal wave forms.
> Triac's don't output sine wave by a LONG shot.
>
> True RMS measurement are often NOT produced by cheap meters.
>
> (Or so it has been in the past - maybe things are better now??)
>
>
> On Jan 1, 2009, at Jan 1(Thu) 3:26 , Brian Whatcott wrote:
>
> > a wattmeter is now so within reach that it would be a good accessory.
> > This would enable a TRIAC dimmer to moderate the power,
>
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Brian Whatcott    Altus OK    Eureka!