Electronic rotational-speed/time recorder incorporating stroboscopic speed-interval detection

The equipment described in the paper was developed to record automatically the speed/time curve of an experimental homopolar machine undergoing retardation. These retardation tests were being made to determine tooth-ripple losses, and the highest rates of retardation required were beyond the range within which normal visual observation of a stroboscopic disc is practicable. An electronic binary counter and a punch unit provide a speed/time record on punched paper tape, which may be directly processed in a computer programmed to calculate the tooth-ripple losses. The input to the counter can be made from one or other of two independent detector systems. The first operates on the principle of the stroboscope, interpreted electronically, and is thus essentially a rotational speed-interval detector. As this system presents novel features, it is dealt with in more detail. The alternative system, based on counting revolutions in known time intervals, is utilised in existing commercial instruments. The maximum rate of retardation which this equipment can handle is about 1000 rev/min per second.