Using current sensors (transformers) for input to microcontroller

moty22 said:

Please read my blog #18.
Instead of using 2 CTs in chain you can look for CT with turns ratio of 1:5000 or 1:1000 and 25A primary. They are available.
Alternatively if you take a 5VA transformer of lets say 120v to 12v the primary will have about 2000 turns. wind around the primary or secondary one turn of 25A wire and you have your home made CT. Because you don't know the number of turns you will have to put known current through the 1 turn, and measure the voltage on 100 ohm resistor across the primary (the 120V terminals, the 12V terminals aren't used at all) . The number of turns is the ratio of the current through the 1 turn to the current through the resistor.

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Reloadron said:

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You got me curious? So why use a burden resistor chased by a precision rectifier?

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ADWSystems said:

Our train just passed each other. I was speaking of wrapping the source wire (carrying 25A) through the CT a second time.

On another note, I'm not following your words, but I do follow the math. The picture shows 50:5 and 5:1000, so 25A source reduces to 2.5A, then 2.5A is reduced by 5:1000 from 2.5A to 12.5mA. The description says "getting another 50:5", by which the 2.5A would be reduced by 50:5 from 2.5A to 0.25A.

That is unless I'm not following something.

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