Means for recording phenomena by means of standing waves

摘要

718,008. Recording-appamtus TRIGGS, W. W. (Technicon Cardiograph Corporation). Oct. 30, 1952, No. 27336/52. Class 106 (4). [Also in Groups XXXVI and XXXVIII] The magnitude of a variable is indicated or recorded by generating a standing wave of electrical energy along a pair of parallel conductors, varying a nodal position along the conductors in accordance with the magnitude, and transforming such variations into a visible indication or record. In one embodiment, an oscillator 10, Fig. 1, is connected to a pair of parallel conductors 20, 22 short-circuited at the remote end 24 to produce a standing voltage wave W along the conductors. The oscillator is frequency-modulated by an input voltage at 12 proportional to the magnitude to be indicated so that the voltage node D moves along the conductors, e.g., between the points A, B, in accordance with the magnitude variations. In a second embodiment, Fig. 2, the same effect is produced by supplying the conductors 20, 22 from a constant-frequency oscillator 30 and applying the signal input voltage at 34 to vary a thermionic reactance 32 connected across the ends of the wires remote from the oscillator to vary the effective length of the wires in accordance with the variable magnitude. The wires may be located in a glow-discharge tube whereby a varying glow-discharge along the wires is produced according to the wave shape, which may be photographed. Alternatively, and as shown, a thermally or other voltage-sensitive paper 26 is moved at constant speed transversely between the wires and between the points A, B, the paper being discoloured except at the nodal point D as it passes between the wires. The nodal point D thus functions as an inertialess pointer moving across the record paper. The device may be used for dynamic strain testing. Instead of using a nodal points as an indicator the standing wave may be arranged with harmonics which produce sharp peaks in the wave form, these peaks, only, being of sufficient magnitude to actuate the record paper.