I am looking for a way to measure my alternators amp output in real time. I want it to be a permanent in-line unit but the one thing i have tried doesn't seem to be working...that or i just fried the unit and didnt know it.

3 1/2 GREEN DC 200A LED Digital AMP Panel Meter + Shunt - eBay (item 320526853443 end time Aug-01-10 18:35:33 PDT)

Is there anything else out there that can do this?