Patent GB-640061-A (GB)
Title: Analyzers for the automatic execution of cumulative curves showing the algebraic variations of a statistical distribution
IPC: G06G7/20
Filed: 1948-01-01
Abstract: 640,061. Recording-apparatus; statistical apparatus. METROSTATIE SOC. ANON. Jan. 1, 1948, No. 79. Convention date, Jan. 4, 1947. [Classes 106 (i) and 106 (iv)] [Also in Group XL (b)] A system for investigating the distribution of variations of a variable from its average comprises recording by perforations successive values on a strip, defining the average on the strip by a line, scanning the strip transversely in register with each perforation in succession to define the distance between the perforation and the average line, measuring said distances or any desired function thereof and adding to form an accumulating graph whose ordinates at any time are proportional to the sum of the values of the functions of the distances previously scanned. A strip 1 with average line 3 passing through the distribution of perforations 2 moves step-by-step beneath a scanning carriage 4 reciprocated at right-angles to the length of the strip, for instance by screw-thread means 5. The scanning carriage 4 carries three electric contact feelers 6, 7, 8. The feeler 6 is insulated from a conducting track 9 by the strip 1 except when passing over a perforation and electromechanical means secure that only when crossing a perforation 2 in a direction toward the average line 3 is a circuit closed to release, through a clutch 22, means for measuring the distance and for beginning the graphical accumulation of said measure to the previously recorded total, the clutch 22 being disconnected, the measure completed and the record interrupted when the feeler 7 crosses a small conducting part 11 of its otherwise insulating track 10. The clutch 22 is electromagnetic in type and rotates in one direction or the other according to which part of the conducting track 12, 13, separated by a small insulated section 14. the feeler 8 is scanning and accordingly varies with the algebraic sign of the deviation. The tracks 10 to 14 are carried on a platform 15 which may be adjusted by sliders 16, micrometrically if desired, to bring the small sections 11, 14 over the average line. At the end of each scanning operation, the feeler 6 rides up on to an insulating cam 24 and two clamps 23 release the strip 1 which is advanced by ratchet 17 and sprocket drum 18, a record strip 21 being advanced at the same time. The successive measures are accumulated by means 25 which drives a stylus 19 through a rack 26. When the stylus 19 reaches an edge of the strip 21 a cam 27 or 28 releases it from the rack and a spring 29 returns it suddenly to zero, where it is re-engaged by the rack. When the means 25 reaches the end of its stroke, a contact 30 or 31 is closed to operate an alarm. Alternatively the rack 26 and member 25 may be of circular form and means may be provided for counting algebraically the number of shifts back to zero. The stylus 19 may be constrained to move in accordance with other functions of the measured distances by forming the scanning carriage control screws 5 with varying pitch or by inserting suitable mechanism 32 between the clutch 22 and stylus 19. In a modification, Fig. 3, an opaque chart 1 with perforations 2 and an average line 3 moves at constant speed over illuminated transparent slots OAB, OCD, so that the line 3 always registers with the point O, the luminous energy received by a photo-cell in a camera obscura placed over each slot is then proportional to the time the perforation takes to pass the slot, i.e., it depends on the shape of the slot, and also to the intensity of light along the slot, which intensity may be controlled by introducing a screen of variableopacity. If, e.g., the intensity of illumination is uniform then if the lines BO, OD are straight, the luminous flow is proportional to the variations, if they form a parabola then to the squares of the variations. The two electric currents derived respectively from the accumulation of positive and negative variations are associated in a device for producing their algebraic sum, e.g. in an ampere-hour meter with two differential windings or in a double flux meter with two differential windings. A graph of the accumulated variations may be obtained photographically from a luminous beam reflected from a mirror rotated by the said device. The mirror may be polygonal, the trace reverting to zero each time the beam falls on another surface. Periodic functions in the data under analysis may be eliminated from the accumulations by placing a second luminous slot with associated electrical devices at a distance along the chart equal to half the wave-length of the periodical phenomenon predominating when equal variations of opposite sign will cancel out. Alternatively the triangles OAB, OCD may be similarly displaced longitudinally. If a slot of uniform breadth is used then its breadth may be at least half the said wave-length. In a third modification, Fig. 7, rectangular perforations are used and one of the strips thus cut out is fed through an optical analyzer with a luminous slot of uniform breadth, the luminous flow then being proportional to the amplitude of variation recorded. A triangular slot would provide for accumulation in proportion to the squares of the variations. An accumulation similar to that of the second embodiment is then derived by opposing to the variable photoelectric current produced a current proportional to the average value of the variable. Periodical variations may be eliminated in the first embodiment described by providing two scanning carriages separated by half a wave-length, their respective accumulating means acting on a single receiver through sun-and-planet gear.