Ion air density sensor for atmospheric pressure and altitude measurements

摘要

990,047. Pressure measuring apparatus. BENDIX CORPORATION. March 7, 1961 [March 16, 1960], No. 8215/61. Heading G1N. [Also in Divisions G3 and H1] A pressure measuring device, e.g. altimeter, comprises an ionization gauge 5, Fig. 3, having a chamber 34 for receiving, through the conduit 80, a sample of gas the pressure of which is to be measured, anode and cathode electrodes in the form of three coaxial cylindrical tubes 50, 60 and 56, the inner and outer ones 50 and 56 of which are electrically interconnected to form the anode, radio-active material on the cathode 60 for ionizing the gas sample in the chamber, a thermostatic heating arrangement for maintaining the temperature of the gas sample substantially constant and electrical means connected between the anode and cathode via the conductors 37 and 62 to provide an output signal directly proportional to the density of the sampled gas maintained at said substantially constant temperature and hence directly proportional to the pressure of the gas. The cathode 60 and anode 50, 56 are connected through the conductors 62 and 37 to a D.C. source 70, Fig. 1, in series with a resistance 72 across which an output signal is passed to the indicating device 76 which can be of the type described in Specification 863,562. The heating arrangement comprises an electric heating coil 14, Figs. 1 and 2, surrounding the ionization gauge and controlled by bi-metallic switches 17, 18 in the circuit 24 selecting the parts 15, 16 of the coil 14 for coarse and fine temperature regulation. The gauge 5 and coil 14 are contained within a casing 7 filled with heat insulating material 26 such as fibreglass.