I want to know how does the universal current sensor work?

A current sensor is a device that detects electric current in a wire, and generates a signal proportional to that current. The generated signal could be analog voltage or current or even a digital output. The generated signal can be then used to display the measured current in an ammeter, or can be stored for further analysis in a data acquisition system, or can be used for the purpose of control.

The sensed current and the output signal can be:

Alternating current input,
analog output, which duplicates the wave shape of the sensed current.
bipolar output, which duplicates the wave shape of the sensed current.
unipolar output, which is proportional to the average or RMS value of the sensed current.
Direct current input,
unipolar, with a unipolar output, which duplicates the wave shape of the sensed current
digital output, which switches when the sensed current exceeds a certain threshold