GB823009A - Force-ratio measuring apparatus - Google Patents

Abstract

823,009. Electrical measuring systems. SPERRY RAND CORPORATION. Dec. 6, 1957 [Dec. 6, 1956], No. 37978/57. Class 40 (1). [Also in Group XIX] Force-ratio measuring apparatus comprises a lever 2, Fig. 2, forces F 1 and F 3 being applied at distances a and b respectively from the fulcrum 1 to produce opposite torques upon the lever, and the line of action of F 3 being displaced by an angle # from a line normal to the lever such that the lever is maintained in an equilibrium position in which # = # [F 1 /F 3 ]. Fig. 3 shows a Mach meter in which the lever 2 is acted on by two bellows 5, 9, in a sealed chamber 4. A pitot tube 21 puts the interior of chamber 4 at static pressure (P s ) and the interior of bellows 5 at total pressure (P t ) so that bellows 5 and bellows 9, which is evacuated, exert forces representing P t -P s , and P s , respectively. Deflections of the lever 2 are communicated to an inductive pick-off 17, the output of which energizes a potentiometer 18. The wiper 19 of potentiometer 18 is positioned in accordance with the expansion of a third bellows 30 respontive to P t -P s to compensate the effects of altitude variations, the potentiometer output being amplified at 20 and fed to a servomotor 15 which drives a shaft 12 to rotate bellows 9 until the beam is restored to its null position. Motor 13 also controls a pointer 27 associated with a scale 26 which may be calibrated to read a Mach number direct, and a potentiometer 29 which may be shaped to produce a potential which is a direct measure of Mach number. In an alternative method of compensating altitude variations, bellows 30 operates a pick-off whose output is used to bias one of the valves in amplifier 20, which is then supplied directly from pick-off 17.