It is easy to set up and measure the voltage. The power supply is AC resource. You can follow my step to do; 1. Turn to AC mode position on the meter. If you have a multimeter has auto detection function, you don't need to do this step. 2. First, use two probe plug in two holes of the power supply. 3. The monitor will show a value of AC voltage. If the source does not have power. It has not value. That's it . Read more function in here.