"JGBOYLES" wrote in message
...
1500W into 50 Ohms yields 274V which you then divide by 27.4 to obtain
10V.
As you already have 10V by divider action, what do you need to
multiply?


It all works for me in Excel. Squaring the voltage eliminates the need for
any log stuff.

E = Root (P*R)

Scaled V is V / 273 but you'll have to go further to stay in the dynamic
range of the multiplier. V^2 should be around 10V or whatever the mult can
output.

W V scaled V V^2 V^2/10 Output ratio
1500 273.9 10 100 10 1
500 158.1 5.77 33.33 3.33 0.33
100 70.71 2.58 6.67 0.67 0.07



--
Steve N, K,9;d, c. i My email has no u's.

E = Root (P*R)

Scaled V is V / 273 but you'll have to go further to stay in the dynamic
range of the multiplier. V^2 should be around 10V or whatever the mult can
output.

Thanks for checking my calcs. Steve. I had to do what your spreadsheet did by
hand. I should note that since I have to convert the voltage to the multiplier
to DC, at 1500 watts we are working with 273*SQRT 2 or 386 volts. I size the
divider so that 386 this gives 10.0 volts to the multiplier. With a dual
polarity 15VDC supply, the multiplier has enough dynamic range.
73 Gary N4AST

Oh, yea! I forgot the bit about Peak...silly me.
73, Steve K9DCI

"JGBOYLES" wrote in message
...
E = Root (P*R)

Scaled V is V / 273 but you'll have to go further to stay in the
dynamic
range of the multiplier. V^2 should be around 10V or whatever the mult
can
output.

Thanks for checking my calcs. Steve. I had to do what your spreadsheet
did by
hand. I should note that since I have to convert the voltage to the
multiplier
to DC, at 1500 watts we are working with 273*SQRT 2 or 386 volts. I size
the
divider so that 386 this gives 10.0 volts to the multiplier. With a
dual
polarity 15VDC supply, the multiplier has enough dynamic range.
73 Gary N4AST

Hi Gary,

I like the topic of discussion. I've been working with the AD633's for
several years now. I'm wondering why you vered away from the V*I idea.
That would make your calculation good for any load. Instantaneous V
times instantaneous I will give the answer whatever the relative phase
happens to be. Maybe I'm missing something?

Hi Jim, this didn't show up on my ng reader for some reason, hope you don't
mind me replying on the ng.
The reason I didn't the V*I route, which as you say, is the obvious way to
go: I did not feel I could get accurate V and I samples over a wide range of
RF frequencies, with my limited knowledge and resources. I thought a simple
resistive voltage divider would make it real simple, and somewhat frequency
independent. I am now finding through the responses I have gotten, that
resistors will be frequency dependent as well. Darn.
I recently tried to use 633s in an application at 60hz to detect when a very
large generator went from producing power (generator) to absorbing power
(motor). I found that the potential and current transformers I was using
introduced an unacceptable phase shift from primary to secondary. I tried
several different types but finally took another approach. This is probably
another reason that steered me away from the V*I solution.
If you have a simple way to get accurate V and I samples for say 3-30MHZ I am
all ears, and forever in your debt.
73 Gary N4AST