A method and apparatus are provided for obtaining the rotational speed of a pump system or other suitable rotating equipment having a self-contained pump electrical equipment power supply. The method features, before being rectified, directing one phase of AC power through a zero crossing circuit that identifies an instant of time the AC voltage crosses from one polarity to the other polarity and triggers a square wave pulse for each instant time. In operation, the AC voltage is detected when it crosses from a negative polarity to a positive polarity, or vice versa. The method also includes steps for measuring the period of the square wave pulse and calculating the speed of the pump or other rotating equipment.