GB1086381A - Apparatus for measuring vapour concentration - Google Patents

Abstract

1,086,381. Measuring electrically. A. LEES. Aug. 24, 1964 [May 22, 1963], No. 20479/63. Heading G1N. In a device for measuring the concentration of moisture or other vapour of the kind described in Specifications 732,969 and 805,051, comprising a first electrode bearing a porous vapour-sensitive dielectric layer, and a second electrode formed by a vapour-permeable conductive layer deposited on the dielectric layer, a conductive connection with the second electrode is made by an open helix of thin conductive wire tightly wound over part of the second electrode and held in place by electrically conductive cement. As shown, Fig. 2, an aluminium rod 11 constituting the first electrode is anodized to form a dielectric layer 12 of Al 2 O 3 on part of the length thereof. A sleeve 13 of epoxy resin, ceramic &c. is formed on unoxidized rod 11 and overlaps oxide layer 12, after which a second electrode 14 is formed, as by the vacuum evaporation of aluminium. A thin copper wire 15 is wound tightly around the electrode 14 on sleeve 13, and is cemented in place using conductive cement 16. A plastic film 17 is then applied. The device may be treated as described in Specification 867,046 to mitigate the effects of ageing. Electrode layer 14 may alternatively be of gold or copper, and wire 15 may be of silver. In Fig. 3, such a device 25 is connected as shown in a diode pump circuit, containing a meter 22 and supplied with A. C. In Fig. 4 (not shown), two devices (28, 29) are connected in a differential arrangement, the output being amplified by a transistor (43) and indicated on a meter (44).