Patent GB-1193841-A (GB)
Title: Apparatus for Testing Air Data Instruments
Inventor: DAMREL JOHN BENJAMIN JR
IPC: G01P21/02
Filed: 1967-07-10
Abstract: 1,193,841. Testing air pressure gauges. TEXAS INSTRUMENTS Inc. July 10, 1967 [July 15, 1966], No.31585/67. Heading G1L. In apparatus for testing and calibrating air data instruments, such as altimeters, the interior of a Bourdon tube 10a of a unit B is highly evacuated and then plugged 27 and starting from a "null" position of a transducer 12a knob 48, Fig. 2, will be turned to rotate a transducer-carrier worm wheel 15 by the angular degree as indicated on the counter 47 previously calculated as corresponding to absolute atmospheric pressure existing at a predetermined altitude, and with an arm 55 of a meter switch on a servo-contact 56 light reflected from a mirror 30a will fall unevenly on photo-cells within and beyond (51, 52) the transducer 12a and cause a current to pass through a line 50, which current, amplified, will pass through a servocontrol switch contact 39 to a motor 35 to actuate a regulator valve of a regulator 14a to allow gas to pass to a pump 18 from a space in a capsule 9a about the Bourdon tube 10a to cause the capsule 9a pressure to be maintained and the mirror 30a to be rotated to its null position and then disconnect current flow through the line 50. Thus the pressure standard will be maintained constant by the regulator and supplied to the altimeter to be calibrated. The polarity of the currents supplied will be such to operate the motor 35 in the correct direction to connect either a pressure source 19 to the vacuum pump or the vacuum pump 18 to the interior of the capsule 9a. To provide a test standard pressure for an air speed indicator at a particular altitude the interior of a capsule 9 is charged at the absolute pressure existing at the altitude and a transducercarrier worm wheel associated with the capsule 9, is rotated, to the calculated angular degree which would result when the Bourdon tube 10 is subjected to the total or pivot tube pressure at a predetermined test air speed at that altitude. For this purpose, the absolute atmospheric pressure at the altitude being considered, as generated by unit B, is transmitted by branch line 26 to a fitting 5. Then servoamplifier 13 and regulator 14, including parts 55, 58, 40, 35 and 34, Fig. 2, will be operated to automatically direct fluid-pressure from source 19 or vacuum from pump 18 into the interior of Bourdon tube 10 to rotate the mirror 30 to the "null" position with respect to optical transducer 12. The resultant standard test pressure will be held by the regulator mechanism and a pressure supplied through piping 24 will be the total pressure of the air speed to which the meter is being calibrated, while the absolute atmospheric pressure will be transmitted to line 23 to its proper fitting. As before incremental air speeds will be checked to fully calibrate the air speed unit. Other absolute and differential pressure instruments may be calibrated by the apparatus, including mach meters and pressure ratio transducers. The instrument may also be utilized for measuring unknown perameters to simulate an accurately calibrated instrument such as altimeters or air speed meters.