I am working on a project that will allow me to plug a device into my circuit and the circuit will display the power the device is using on an LCD. I am going to use a PIC microprocessor for this project.

Obviously I am going to need to measure the current and the voltage of the device and multiply these together with the PIC. I am unsure of the best way to go about making these measurements. I was thinking that I might be able to use some kind of op amp configuration; maybe a difference amplifier?

I plan on powering the device with a 12v supply. I am assuming I will need to adjust this voltage for the PIC as I believe it can only support plus or minus 5V.

I appreciate any and all help with this. Thank you in advance.

 

Something like this? - http://www.thinkgeek.com/gadgets/travelpower/7657/

Doing this yourself is more than a bit dangerous. The line voltage can be reduced to a safe level with a transformer, but you have to have the full line present to monitor current. Everything can be housed safely, but doing development can expose you to lethal voltage.

 

something exactly like that...yes

 

You could use these and keep your exposure down: http://www.amploc.com/AMP SERIES 25-300.pdf