Patent GB-776040-A (GB)
Title: Improvements relating to analogue computers
IPC: G06G7/38
Filed: 1955-06-10
Abstract: 776,040. Analogue computers. SPERRY CORPORATION. June 10, 1955 [June 11, 1954], No. 16822/55. Class 37. [Also in Group XL (b)] An analogue computer for tracing the paths of under-water sound rays as predicted from sound velocity versus depth data includes a first integrator, means for setting an initial condition into the first integrator, a second integrator, means for setting an initial condition into the second integrator, an electronic function generator for producing an output voltage whose magnitude is a predetermined function of the magnitude of an input signal, the output of the function generator being connected to the input of the first integrator and the input of the function generator being connected to the output of the second integrator, and means for indicating the change in output voltage of the second integrator as a function of time. The described apparatus is adapted to trace on a C.R.T. 30 the family of rays emanating from a source at depth y and corresponding to the equation y = k/v dv/dy, where v is the velocity of a sound ray and k is a constant. It includes integrators 22, 24 which may comprise doubleended amplifiers employing negative feedback through capacitors to perform the integration and of which the output of integrator 24 which is proportional to the depth y is connected to the X-plates of a C.R.T. 12 in a function generator 10, the output from which is fed to the integrator 22. This generator 10 also includes an amplifier 18 connected to the Y-plates of C.R.T. 12 and to a photo-tube 16 between which and the C.R.T. is disposed a mask 14 having its upper edge conforming with the dv plotted curve of function - against depth y. v.dy Amplifier 18 is so biased as to maintain the spot on the C.R.T. screen in line with the upper edge of mask 14 so that the output from the amplifier is varied in accordance with function dv/v.dy. Since this output is fed to the integrators 22 and 24, the output from the latter varies with the depth y of the ray. This output is fed through a bridge rectifier reflection circuit 32 which maintains a constant polarity even if the polarity of the output of the integrator 24 changes, to the Y-plates of C.R.T. 30, the X- plates of which are connected to sweep circuit 34 so that a ray is traced on the screen of this C.R.T. A synchronizing circuit 39 is connected to sweep circuit 34 and to initial control circuits 26, 28 so as to periodically reset the initial condition on the integrators 22, 24 and thus allow the continual re-tracting of a sound ray path on C.R.T. 30. Motor drive 46 is provided for automatically altering the initial angle control of circuit 26 so that successive sound rays are traced. The depth control circuit 28 is manually adjusted. Circuits.-Each integrator comprises, as shown for integrator 22, a double-ended amplifier 52, 54 with negative feedback capacitors 66, 68 for performing the integration. The pentodes 52, 54 are cut off 60 times a second when a synch pulse from a pulse shaper 44 drives the control grids of triodes 74, 76 in the circuit 26 negative and connects the input ends of capacitors 66, 68 to a fixed negative potential through diode limiters 78, 80 and a potential divider 82, 83. During each synch pulse pentodes 98, 100 are rendered conductive so as to connect the capacitors 66, 68 to an adjustable potentiometer 88 and give them an initial charge corresponding to the initial angle of a sound ray to be traced. Potentiometer 88 is driven by motor 46 so that the same initial angle signal is fed to the integrator 22 only once for 12 revolutions of the motor, during which time 720 traces, each with a different initial angle, are provided on C.R.T. 30.