ES351925A1 - A device operating as an altimeter and an altitude stabilizer - Google Patents

Abstract

Apparatus for measurement and control of the altitude of an aircraft comprises first and second radiation sources and a radiation detector to detect the pressure of the atmospheric air, the detector being used in association with the first source when measurements of altitude are to be carried out, and with the second source when the output of the detector is to be used to control the altitude, the detector circuitry including a gate through which the detector output can be coupled to a servo mechanism, operating on the elevator or engine of the aircraft, when control of the altitude is to be undertaken. The radiation manometer comprises a chamber 1, through which atmospheric air can flow, containing a surface barrier diode of N-type silicon 2 mounted on a vertically displaceable arm 5. The two radiation sources are [alpha]-emitters, one 3 being of Am241, formed as an electrolytic deposit on a platinum disc, and the other 4 being a relatively thick disc of enriched uranium. They are mounted on a rotatable table which turns between two positions bringing either one of the sources in line with the detector 2. When source 3, which is effectively a monochromatic source, is operative the output of device 9, an integrator or ratemeter, operating on pulses from the detector which have passed through pre-amplifier 7 and threshold amplifier 8, is connected through gate 11 to operate a servo mechanism 12 controlling the aircraft elevator or engine, whereby a constant altitude may be maintained. When source 4, emitting a much wider range of energies, is operative the gate is closed, and the apparatus may function as an altimeter, the indicator 10 being graduated in altitudes. In altitude measurement, to obtain maximum sensitivity the threshold level of amplifier 8 is set as low as possible, by control C 3 , but high enough to suppress noise pulses. The sensitivity of the apparatus is affected by variation of the sourcedetector distance and several scales are provided on meter 10 corresponding to particular values of this distance. In altitude control, the threshold level is set to define the altitude to be kept. This is possible since, with the americium source, the pulse count rate is affected greatly by very slight altitude changes, up to a certain height, Fig.6 (not shown). The effective source-detector distance is adjusted when controlling altitude, for different altitude ranges by the introduction of respective filters for each range e.g. of polyester film or polyester film plus a gold filter. The apparatus is calibrated in a standard atmosphere and so corrections to the measured altitude are necessary to allow for air temperature variations with altitude.