Improvements in and relating to the detection of gases, vapours, dusts, smokes or other impurities in air

摘要

529,626. Control systems. KENWELL RADIO, Ltd., and SHARLAND, L. A. June 5, 1939, No. 16459. [Class 40 (i)] The presence of impurities, gases, dust, smoke &c. in air is detected and estimated by causing the air to pass over a source of heat, such as a heated wire 19, whereby the resulting variations in the heating effect alters the capacity of a thermally sensitive condenser 20, which is in a circuit responsive to small capacity changes. Examples are given including an oscillator valve 14 with milliammeter 17 in the anode lead, a circuit of the beat frequency valve oscillator type, and a capacity-resistance bridge circuit. The indicating or recording meter may be in a rectifying circuit coupled with one of the inductances.