Patent GB-581977-A (GB)
Title: Systems for recording one or more variable magnitudes
IPC: G01D1/14
Filed: 1942-10-09
Abstract: 581,977. Electric signalling systems. KEINATH, G. Oct. 9, 1942, No. 14206. Convention date, July 12, 1941. [Class 40 (i)] [Also in Group XIX] An apparatus for recording the value of a variable quantity, particularly for determining the oscillatory magnitudes of a vibrating part of a work-piece, machine or complete structure, such as high-speed boats, aeroplanes or bridge comprises an electric circuit responsive to said variable, a measuring circuit connected to said responsive circuit including a relay responsive to a given minimum voltage, a potentiometer device with a movable contact member having a rate of change varying progressively with uniform movements of the contact member; a recording device having a member movable simultaneously with the contact member, and means controlled by the relay to produce a record. For measuring a plurality of variables, a number of measuring circuits and associated potentiometers are provided and a single contact member co-operates with the potentiometers in succession. As shown in Fig. 1. applied to testing vibration conditions on aeroplanes, one or more transmitters or pickup devices 111 to 116 similar to those used in sound recording or reproducing are mounted in different parts of the aeroplane with their leads connected to a coupling member 71. The engine 45 or a part driven thereby is connected to a coupling member 73. The other elements of the apparatus form a portable testing set and include a potentiometer contact device 120, a recording device 40, an amplifier 50 and a relay 60. The contact device comprises a set of resistance units 121 to 126 and a movable contact 127. Each unit as shown in Fig. 3, has a bank of twenty-one contacts to divide the resistance (124) into twenty steps, the various steps being graded in accordance with a hyperbolic law to obtain a linear record. The resistances 121 to 126 are connected at one end to a common conductor 32 through series resistances 131 to 135 while the other ends and the conductor 32 are connected by leads to a coupling member 72 engageable with the coupling member 71. The conductor. 32 and movable contact 127 are connected to the input side of the amplifier 50, the output of which is connected to the relay 60. The recording device 40 comprises a drum 41 driven by a constant speed motor and a stylus 42, the shaft of the drum being connected to the movable contact 127 to drive it in synchronism therewith. The recording stylus is mounted on a screwed shait 43, Fig. 2, driven by a tachometer 47 connected by a flexible shaft 44 and coupling member 74 to the coupling associated with the engine 45. The record is produced electrolytically on the closure of relay contacts 62 to complete the circuit from the battery 63 through the stylus 42. The length of the record depends on the length of the path still to be traversed by the contact 127 and is determined when the voltage drop between the conductor 32 and the contact 127 exceeds a certain minimum. Any other suitable form of recorder may be provided such as a pen or condenser discharge circuit may be controlled by the relay to produce a dot record.