A Continuous Electronic Pulse-Rate Indicator and Recorder
Myron M. Schwarzschild, Moses C. Shelesnyak · Review of Scientific Instruments · 1942
A circuit is described which is operated by the cardiac action current impulses in which the reading of a meter is a nearly linear function of the pulse rate. The impulses are amplified and applied to a trigger tube which sets off a gas discharge tube discharging a condenser at each beat. The charge transferred at each beat is independent of the shape of the action current wave within wide limits. The meter, shunted by a large smoothing condenser, reads the average current and is calibrated in beats per minute. The instrument may be connected to any suitable type of recording millivolt meter to obtain a continuous record of rate. The device may be used for indicating or recording the rates of any quasi-periodic phenomenon, in the range of frequency from 20 to 400 per minute, if at each period an electrical impulse of the order of 1 mv can be provided.