I have searched the site and seems like the ideal burden resistor for a SCT 013 CT and a 5V Arduino is a 33 ohm resistor.
Some people seem to disagree, any thought on that?
Also, which would be the ideal resistor for the bigger SCT 019 CT that supports 5-200 Amp
I see there are a couple of different types of the SCT 019 variety: http://www.yhdc.com/english/productshow.asp?id=225
You wont need a burden resistor for the voltage output type.
Have a look at this page, it details how to calculate the burden resistor for the current type: http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
I have the SCT 019-000 that doesnt have a burden resistor
So it looks like that it's 6000 turns so the calculation for a 5V arduino gives me 53 ohm. Closest would be 51 ohm
I agree with this calculation.
I reproduced the setup with the SCT-019-000 current sensor and a 54 ohm resistor (supposed to be 56 but I measured 54).
With this value, the calibration constant should be 6000 / 54 = 111.11 (precisely the default of the example sketch).
(Note that this resistor value "may be a little high to be able to read the full 200 A primary current" (Thank you Robert) but unless you need the whole range, it should not be an issue, I suppose.)
Open-source tools for energy monitoring and analysis. This project uses the GNU General Public Licence