The design of an electrodynamic multiplier

An electric-analogue multiplier using an electrodynamic principle is described. An output voltage proportional to the continuous product of two rapidly varying voltages is obtained by the use of crossed electric and magnetic fields in a cathode-ray tube, in conjunction with a photo-electric feedback system. The systematic error in the output is not greater than 2% of maximum output in the frequency range 0¿5 kc/s. The associated electric circuits, which incorporate zero-drift compensation, are described and the origin of error voltages in the output are discussed. An indication is given of methods which may be used to increase the accuracy and speed of response.