I'm in the market for a some inexpensive current transformers that can be used in conjunction with an Arduino to monitor the power usage of devices that consume less than 300 watts on 110V US circuits.
I ran across a part that at the moment looks like it could work. The device is a CSE187L (NetSuite | Page Not Found) from Triad Magnetics. The fact that they're not clamp on or pass through but rather need to be wired in-line is not a problem (or rather I don't see any problems for my application).
I ask here because I'm suspicious of the the fact that they cost less than US$3, they're in stock (it seems that things that I want are so often non-stock), and they at least appear to, at this late hour, meet all my needs. Thanks for the help.
Probably the simplest way to interface to the Arduino would be use connect the current transformer to an AVAGO HCPL-7520. Available from Mouser for a little over $3.00.
It could greatly simplify your solution. Attach the transformer to the +/- inputs (with a low ohm burden resistor) and then read the Analog output value with an ANALOG PIN on the Arduino.
For $3 you get what you pay for. If 10%+ error and a fair amount of non-linearity is good enough for your needs then go ahead, but bear in mind you are breaking into the primary 110volt circuit. If you want a decent unit (at 10 times the price) then go for a hall type sensor which offers a feed-through sense hole and outputs a linear DC signal proportional to current over the whole range.
jack