GB368770A - Improvements in or relating to electric negative resistances - Google Patents

Abstract

368,770. Generating and amplifying oscillations. HABANN, E., 44, Stargarderstrasse, Berlin. Aug. 27, 1930, No. 25594. Convention date, April 3. Addition to 367,790. [Class 40 (v).] A powdered resistance having a negativeresistance characteristic as claimed in the parent Specification and suitable for amplifying or generating electric oscillations, has incorporated with it a catalytic substance which is capable of absorbing the medium which the contact substance adsorbs, or it may be placed in a medium which is strongly adsorbed by the contact, the medium being preferably at superatmospheric pressure, or both these measures may be taken together. An oxide melt consisting of zinc oxide and 3 per cent by weight of copper oxide associated with an iron wire or a sulphide mixture associated with a molybdenum wire may be placed in an oxygen atmosphere at superatmospheric pressure. Suitable catalysts for use with oxygen are charcoal, cuprous oxide, osmium, vanadium, and the oxides of vanadium, osmium, manganese, cobalt, nickel, tungsten, and chromium. Platinum, preferably in the form of platinum black, may be employed either as a coating on one or both of the electrodes, or incorporated in the powdered contact substance. To prevent the formation of conductive bridges by coherer action, neutral nonconducting powder as referred to in the parent Specification (e.g. finely divided aluminium or antimony oxide) may be mixed with the platinum black, the mixture then being added to the powdered contact substance. Preferably, however, a nonconducting contact substance such as cerium or thorium oxide is employed. As described in the parent Specification, powdered metal may be added to the negative resistance powder. Powdered alloy of a metal having a good negative resistance with a metal that regenerates well may be employed, or a powder of the firstmentioned metal provided with a coating of the second-mentioned metal. The degree of compression is adjusted to the optimum value for regeneration, the thickness of the layer of powder, usually below one millimetre, being chosen to give the best development of the negative characteristic. The electrodes should be of a refractory metal. The resistance of the powder is broken down at such a small current intensity that it just remains conducting. Specification 368,270 also is referred to. Reference has been directed by the Comptroller to Specification 103,046, [Class 37, Electricity, Measuring &c.].