Abstract: A phase meter and method of providing a voltage indicative of a phase difference between a reference signal and an input signal in which the amplitudes of the two signals are made approximately the same to cancel potential phase errors caused by different amplitudes, and the two signals are provided to two matched comparators, one receiving the input signal and the other receiving the reference signal. The two matched comparators are connected together so as to provide an output logic signal in accordance with a prescribed, unconventional, truth table. The output logic signal is a pulse whose duration is proportional to the phase difference. The output logic signal is converted to a voltage indicative of the phase difference between the reference signal and the input signal. The phase meter is relatively simple to make and a preferred embodiment measures phase shift directly with a 10 mV/degree output at up to 10 MHz.

Abstract: Apparatus for converting the revolutions of a shaft into pulses including a disc having devices such as slots or reflectors radially spaced around its periphery and light-transmitting and light-receiving fiber optic cables aligned for sensing the devices as the disc rotates. A light source, such as a light-emitting diode, is positioned at the outer end of a light-transmitting cable for providing light, and at least one phototransistor at the outer end of a light-receiving cable converts the light signals into electric pulses. Preferably, the light-transmitting and light-receiving cables are paired, giving successive signals as a slot or reflector is sensed for activating a counting circuit. A single light-transmitting cable is preferably split near the disc to provide two light sources from a single light-emitting diode.