AN ELECTRICAL IMPULSE RATE INDICATOR AND RECORDER
William W. Macalpine · Review of Scientific Instruments · 1930
A circuit is described which is operated by impulses and in which the reading of a meter is a function of the rate of the impulses. In the present instance the impulses operate a Weston Model 30 Galvanometer Relay whose contacts discharge a condenser. The condenser is charged up again through a resistance after each impulse, and a microammeter reads the average voltage across the resistance. A smoothing circuit is used between the microammeter and the resistance. Variations of the device may be used according to the nature of the impulses. A Leeds and Northrup Recording Potentiometer may be attached to the device to obtain a continuous record of the rate. In another form, the average voltage may operate on the grid of a tube, the plate current of which operates a more rugged indicating meter than the microammeter. This also simplifies the filter circuit. Means for calibrating the device are discussed.