Noob question about current sensing build

Hi folks! Need a little basic help.

Look the bolder part inside the quote below found at:

Current sensing electronics

1 CT sensor YHDC SCT-013-000

1 Burden resistor 18 Ohms if supply voltage is 3.3V, or 33 Ohms if supply voltage is 5V.

This referred "supply voltage" stands for main source(DC jack) that powers the Arduino OR the output pins(3.3v & 5v) on the board???

I'm stuck with this silly question...
Thanks in advance!

Robert Wall's picture

Re: Noob question about current sensing build

"Supply voltage" actually means the reference voltage supplied to the analogue to digital converter. This is exactly the same as the voltage that the Atmel processor runs on, so it is the 5 V or 3.3 V on the board.

The slightly more in-depth answer: the c.t. acts as a current source, so a higher resistance burden(for 5 V) allows it to generate a higher voltage that uses more of the available range of the analogue to digital converter, which goes from 0 = 0 V to 1023 = supply voltage of 3.3 V or 5 V).

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