This a kWh meter from a TV show. I'd like to know how many disc revolutions make 1 kWh. I think it's somehow coded in the whole data on the panel or could be derived from that information:
I found a formula
P = (3600 * Kh) / t
(t = time in seconds taken by the disc to complete one revolution, P = power in watts)
which gives me 138,(8) revolutions per 1 kWh but I am not sure I used the formula correctly.
Best Answer
The Kh is (indeed) what you're after, and the formula you give seems to be correct, according to wikipedia, 'Electromechanical' section.
P = (3600 * Kh) / t (for one rotation)
If we call the amount of rotations n, we get (P / n) = (3600 * Kh) / t
Or: P = (3600 * Kh) / (t * n)
Where:
That means the unit of Kh is:
So if Kh = 7.2, and it takes 1 hour for the dial to rotate 1 time, you've used 7.2 Watts.
You want (n * kWh). Let's change that into (n * Wh) for now.
Now, we need to change Wh to kWh, so we multiply both sides with 1000:
So for Kh = 7.2 you get 138.89 n*kWh or 138.89 rotations per kWh.
Your calculation is correct. :-)