Non-Invasive Current Sensor - 30A
This non-invasive current sensor (also known as a “split core current transformer”) can be clamped around the supply line of an electrical load to tell you how much current is passing through it. This sensor does not have a load resistor built in, so in most cases it will be necessary to place a resistor across the output to convert the coil’s induced current to a very small measurable voltage.
This particular current sensor will measure a load of 30 Amps nominal at 50/60Hz.
Here you can read how to interface it to an Arduino.