Tom's latest video ... looking VERY promising ...

[qvision]

Well worth the watch and the replicating, as it has been all along :

YouTube - GUESS WATT ?? MPG


Gary.

[bugler]

I don't understand what is exactly going on in the video.

Anyone could explain it for dummies?

[Roland]

Could the Power Factor be playing a role in Tom's watt readings?

I have a question about the "Watt Meter" i have one just like his but i dont know what role the PF has.

Im not an Electrical guy so maybe someone can explain that to me. Thanks

Example;
With my identical Watt Meter, i check the WATT draw and AMP draw when hooked up to my lap top.

The readings are as follows.
21 WATTS - then swicth to volts
120.2 VOLTS - then switch to Amps
0.35 AMPS.then PF
0.47 Power factor

So 120.2 x 0.35 = 42.07 Watts
I assume the Power Factor needs to be factored i some how.
Does the watts reading already factor the PF in?

[gyula]

Hi Roland,

Because laptop power supplies are switch mode types, their mains input impedance is mainly inductive at 50 or 60 Hz (due to the switched transformer primary coil at the input) so the AC voltage and AC current is not in phase like in case of a resistive load like a electric heater or iron etc.

The phase difference is expressed in degrees and the Power Factor number is the cosine value of this degree.

So the phase angle in your example is arc cos(PF)= arc cos(.47)=61.96 degree, this must be the phase angle between the 120V ac voltage and the .35 A AC current feeding your laptop.

The formula for power when AC voltage and current is not in phase (i.e. the phase angle is not zero or near zero degree, cos(0)=1) is:

Power=V*I*cos(theta) where theta is the phase angle between V and I.

Now multiplying your 42.05W by the PF=.47 it gives 19.76W, pretty close to what your meter showed (21W).

So the Watt display is calibrated by the actual PF involved, it is factored in.

Gyula

PS Some good reading on this: Calculating power factor : POWER FACTOR
(It shows also how to improve PF when it is caused by inductive loads, by compensating the inductance part with an equivalent AC impedance value capacitor.)

[FRC]

Looks the same

The video looks like the Bedini sale video.

YouTube - MODIFIED ELECTRONIC BOX SALE.MPG

Do not know what the point of it is.

FRC