Help me measure the current in each cycle of sinewave

[zezito]

can any one help me!

I there!
i need to measure the current in each cycle of a sine wave from a tranformer 20V 50A. i tried to use two diodes (www.IRF.com 70hf40) in anti paralel positions. Using a osciloscope i realize that the two cycles passed in each diode!!! i used others diodes and it happend again! any one have an idea why this is happennig?

 

[jorgito]

can any one help me!

Hello zezito,
I'm not shure about what you wants to do.
Are you using a current probe in each diode?
Why not a single resistor in series with load?
A WORD OF CAUTION:
You may need a floating measurement, or you could short-circuit 50A trough the scope's ground!
Hope this helps

 

[DarkJedi]

Re: can any one help me!

My guess is you have something like this figure, is not well drawn but u get the point, when a diode is normally pollarized the other is inverse, lettin the wave go throught, when the other part of the wave comes, it happends the same, so.... you always get the same wave.

 

[echo47]

can any one help me!

Anti parallel? Two cycles? Your description is puzzling.
Can you attach a gif or jpeg schematic of your circuit?

 

[zezito]

Re: can any one help me!

please look at the attached file!!
do you think it will ever work?
anyone have ideas to measure and count the current in the positive semi cycle and in the negative semi cycle??

 

[jorgito]

can any one help me!

Attached? where??
ok.. I see it, excuse me.

Seems OK to me.
But you could not use current transformers or anything designed to work with AC because you are measuring positive or negative pulses only.

 

[Kevin Weddle]

Re: can any one help me!

I think it's your ammeter. These things can be tricky because they are very specific in how they are used. It is probably looking for both cycles and I would use voltage as a way of looking at it. You will definitely get something because you have it set up properly. So the reading might be half, but I would not bet on it.

 

[daojx]

can any one help me!

From the circiut you set up, your observation by osciloscope was absolutely correct, as you were
observing the voltage acrossed the two diodes and
they were paralled. But if you can observed the current in each branch, thing should be different.

 

[kgl_13gr]

can any one help me!

what sort of amperometers are you using? consider that many ac amperometers measure rms value