GB581382A - Improvements in electrical indicating and recording systems - Google Patents

Abstract

581,382. Electric indicating systems. KEINATH, G. March 16, 1944, No. 4944. Convention date, Dec. 24, 1942. [Class 40 (i)] A recording mechanism which is controlled in dependence upon two variable quantities employs two Wheatstone bridges in which the resistance arms 211, 221 are varied in accordance with the two quantities. The contact arm 214 of the potentiometer 213 in the first bridge is rotated continuously with the recording drum 245 so that a point of balance is reached every revolution, thus operating relay 215 to discharge condenser 283. The contact member 224 of the potentiometer 223 in the second bridge is driven by a step-by-step motor 241 which is operated by discharge of condenser 283 when both relays 215, 225 are operated, that is when both bridges are balanced, a mark being made on the recording sheet at the same time. The voltage across resistance 221 is rising continuously so that when a point is reached where the bridge is balanced relay 225 is operated and the contact member 224 driven on one step by motor 241, the bridge thus becoming unbalanced again. Time marks are made on the recording sheet by a stylus 264 moved in proportion to time by motor 261. In Fig. 5 (not shown), a rotary reversing switch is included in the circuit of the step-by-step motor so that the motor may be reversed if the voltage across the corresponding variable element decreases. In this arrangement, the voltages across the variable elements are applied directly across the potentiometers, the relays being operated when a certain "threshold" voltage is applied to them. In another modification, Fig. 9 (not shown), the stylus is driven. by a motor which is stationary when the bridge is balanced, but when there is no balance a relay is operated so that the motor drives the contact arm of the potentiometer with the stylus into a position of balance.