uxcell SCT-013-020 1M 3.5mm Output Cord Split-core Current Transformer 20A 1V

I've bought a couple of these SCT models over the past few years for monitoring current on household circuits and have found them to be reliable and sufficiently accurate for my needs. I collect the measurements using a Particle Photon and some simple firmware to do analog data acquisition. With this setup I can generally compute RMS amps within a couple percent of readings made by a Kill-a-Watt monitor.Note that this CT won’t measure DC current; you'll need a different type of device for that. Also, to do analog acquisition of the full waveform, you'll need a bit of additional circuitry to shift the center up from zero volts to something like 1.5-2 volts depending on the range of your analog input. You may also want to consider scaling the voltage down and adding some kind of over-voltage protection if you expect high-current transients in the circuit being measured, as I believe this device will pass that along as a voltage spike above the nominal 1V output range.For more details, the "learn (dot) openenergymonitor (dot) org" website has a nice tutorial on how to wire these CTs up to an Arduino microcontroller.