Submitted by Hendrik van Eeden (not verified) on Sat, 01/30/2010 - 23:24.
Measuring the power factor with the Arduino is not that easy. The zero crossings must be measured with the current to the load as well as the voltage across the load. If the voltage is stepped down through a transformer, it will introduce a phase shift of unknown value. So you need to be able to measure and then correct for the introduced phase shift. Or use a resistive voltage divider which then introduce high (line) voltages into your project. For household purposes the power factor is near to 1 and I believe can be safely ignored.
Measuring the power factor
Measuring the power factor with the Arduino is not that easy. The zero crossings must be measured with the current to the load as well as the voltage across the load. If the voltage is stepped down through a transformer, it will introduce a phase shift of unknown value. So you need to be able to measure and then correct for the introduced phase shift. Or use a resistive voltage divider which then introduce high (line) voltages into your project. For household purposes the power factor is near to 1 and I believe can be safely ignored.