A weight machine sensor includes a force sensor, a position sensor, and a processor. The force sensor is programmed to output a force signal representing a force applied to a pulley-disposed on a cable incorporated into exercise equipment having a stack of weights. The position sensor is programmed to detect motion of the stack of weights and output a position signal representing the motion detected. The processor is programmed to receive the force signal and the rotation signal and determine, from the force signal and the position signal, exercise data including an amount of exercise resistance and a number of repetitions performed.