Measurement of Power Factor?

Thread Starter


Joined May 27, 2014
(This is my first post, hope its written properly) I am planning to make a prototype of smartgrid using Xbees. This project needs a measurement device to detect current and voltages and energy consumption at each node in the system.

My Research:
I finalized my current sensor: ACS712-20A. I am comfortable in coding it to give rms current and also currently i am searching for voltage which i am sure to find.

Issue: I saw tweet-a-watt project but its little complicated for me as it involves soldering and other (lots)details. I want to try calculating power by using P=V*I*Cos(theta). As you can see, we can use a current+voltage sensor to detect V,I (rms values) but how can we calculate power factor-cos(theta).

Idea: In my machines lab, i calculated
powerfactor=(actualwattmeter reading/V*I)... My question of measuring power factor and feeding it to uC might be an amateur idea. If so, Please someone suggest me some good ways to do energy monitor via Xbee(please note that my knowledge on xbee is basic like excluding sleep modes etc..)

Thanks in advance

Thread Starter


Joined May 27, 2014
I found a mathematical solution for my problem. Instead of measuring power factor, it can be calculated.

Real power:
for (n=0; n<number_of_samples; n++)

inst_power = inst_voltage * inst_current;

sum_inst_power += inst_power;

real_power = sum_inst_power / number_of_samples;

Apparent power:
apparent_power = root_mean_square_voltage * root_mean_square_current;

power factor:
Power Factor= real_power/apparent_power