[Kevin Sevcik]

Originally Posted by gc02

If you just want to see the square PWM wave just connect the scope to the output terminals on the Victor. I think you'll get the same results whether or not the motor is connected. If you want to see the sawtooth wave generated by the rising and falling current in the motor you'll need to connect a current shunt in series with the motor and connect the scope to that.

The voltage shouldn't be a simple square wave if there's motor in the system. DC motors generate back EMF and also present a fairly large inductance to the speed controller. All of this will have a definite effect on the voltage that you see on the scope with a motor connected.