A new bunch of Cornell University student projects 2008 have shown up. One of the projects is a device that is capable to measure various AC power parameters in real time. These include:

• Real power
• Apparent power
• Power factor
• RMS Voltage
• RMS Current
• Frequency
• Energy usage (Kilowatt-Hours)

With C# front end application people can monitor parameters in convenient graphs where you can see energy usage and other listed parameters. Despite measurements device can also be switched on/off remotely by using solid state relay and even can be set to turn the power off if pre-set wattage limits are reached. Device is controlled by Atmega32 microcontroller which reads AC data via internal ADC. The rest is left to AVR math, where mostly Floating point calculations are made. PowerBox communicates with PC graphing and control application via UART port. As a result power measurements are quite precise. Calculated error reaches about 2.57% (~1W), what I think is very good results.