I'm building an energy monitor to detect my power usage. The recording should be done on multiple automatic cutouts simultaneously. (20 Channels would be perfect)
At first I wanted to build a device with 10 channels but the planned ATMEGA2560 platform (16 analog in, 10 bit) was not at hand. Instead I opted for a Beaglebone black (7 analog in, 12 bit) with proto-shield I had lying around.
The BBB has only 7 analog inputs but is able to communicate with servers and can drive databases and record log files.
The Build is fairly straight forward. I ordered 10 Current Transformers (1000:1) from eBay for a few Euros. A old Ribbon cable and some Headers provide the Connection.
Schematics: nothing special here, took design from:http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
Accuracy wasn't a priority for me. On normal loads (tested 18W, 60W, 100W, 1200W) the error is around 4% which ist fine for my needs (VAC is not measured).