Measuring and testing – Barometer
Patent
1979-05-18
1981-03-03
Woodiel, Donald O.
Measuring and testing
Barometer
73386, G01L 700
Patent
active
042533350
ABSTRACT:
The altitude of an aircraft is determined by measuring the output of a pressure transducer on the aircraft because the altitude is defined by the atmospheric pressure at that point. In this altitude measurement, the relationship between the altitude and the atmospheric pressure is nonlinear, and most pressure transducers exhibit some nonlinearity. High accuracy altitude measurement, correcting those nonlinearities, have been disclosed in the prior art utilizing a quasi-exponential function generator (QEFG). A quasi-exponential function is an exponential function with a time constant which varies with time. However, the characteristics of the pressure transducer and QEFG are affected by temperature, and there have been no appropriate means other than the use of a thermostat to maintain the accuracy of measurement when the temperature varies. This invention compensates for the temperature variant characteristics of the pressure transducer and the QEFG by changing the constants of the circuit elements of the QEFG and of the output stage coupled to the pressure transducer according to the output of a temperature sensor incorporated in the altimeter. Even the change of nonlinearity, or the change of curvature of the characteristic curve of the pressure transducer is compensated for almost perfectly by this invention.
REFERENCES:
patent: 3693405 (1972-09-01), Shimomura
patent: 3726138 (1973-04-01), Kosakowski et al.
patent: 3729999 (1973-05-01), Shimomura
patent: 3958108 (1976-05-01), Shimomura
patent: 3958459 (1976-05-01), Shimomura
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