|July 2015 Issue||
The Kill-A-Watt is a cheap (~$30) computing 120VAC digital power meter. Plug the KAW into the wall and the appliance under test into it, program in your utility rate in $/KWH and let it run. In addition to measuring voltage, current, real & and aparent power, PF and frequency, it accumulates and calculates energy consumption in KWh.
So long as it is operated off standard line voltage all is well. However, run it off a variable auto-transformer (Variac) and it will quit around 50-60 VAC. I wanted to characterize some small power transformers using open & short circuit tests. While the KAW would be a fine power meter for making such measurements, it needs to be safely modified to operate at the necessarily lower AC voltages.
That is where the cover article I wrote for Nuts & Volts comes in. Check out the full article via the following like to see how I made a safe and reliable modification.