Hi There, it's my project to record current signature of an induction motor and then transfer it to computer, i decided to use current transformer then usb oscilloscope. but there is a problem that i'm quit unaware of using ct. someone please sort me out

 

You buy a current transformer suitable for the current you want to measure. You run one wire from the motor through the center opening of the transformer. Then you place the recommended load on the output of the transformer (important!) and measure the voltage across the resistor with the oscilloscope. The voltage is proportional to the AC current.