power factor correction

Thread Starter


Joined Apr 2, 2010
i am working on my final year project in a nigeria university and i am somehow confused with how to measure pf of appliances in a home, i dont know if anyone has got an idea..


Joined Feb 12, 2009
One way is to use a twin trace oscilloscope. Use one channel to display the voltage and the other to display the current.

The power factor can be calculated by measuring the angle between the current and voltage.

The current is measured by putting a low-value power resistor (say 1ohm 20W) in series with the supply and measuring the volt drop.

BUT! THERE ARE A WHOLE LOT OF SAFETY ISSUES HERE! As the 'scope is connected directly to the mains supply. Isolated inputs are essential.

Might be better to get an insulated box with a mains plug and socket and build a circuit inside that is something like the circuit attached. STILL NO ISOLATION though! SO I AM NOT ADVISING YOU TO ACTUALLY DO THIS.