GB886488A - Improvements in and relating to variable resistors and potentiometers - Google Patents

Abstract

886,488. Inverting. PLESSEY CO. Ltd. May 20, 1958 [May 20, 1957], No. 15998/57. Class 38 (2). [Also in Group XXXVI] A potentiometer (see Group XXXVI) may be used as an inverter by rotating the track at a constant angular velocity relative to three fixed contacts. In a first form, Figs. 7, 8, a base 44 carries an arcuate resistive track 45 joined at one end to an inner circular conductive track 46 and at the other end to an outer conductive circular track 47, and is rotatably mounted with respect to a second base carrying three contact elements 53, 51, 52 which engage with the three tracks respectively. If a D.C. potential is applied between contact elements 51, 52 and the base 44 driven at a constant angular velocity a saw-tooth wave-form is produced at contact element 53. In a second embodiment suitable for producing a sinewave output, Figs. 9, 10, a base 57 has mounted on it a circular track having a low resistance portion 58 extending over 120 degrees, a high resistance portion 59 extending over 120 degrees, and two 60 degree portions 60 of intermediate resistance value, and is rotatably mounted with respect to a second base carrying three contact elements 62, 63, 64 mounted at angular displacements of 120 degrees. If a D.C. potential is applied between two of the contact elements, and the base 57 rotated at constant angular velocity, an approximately sinusoidal output may be obtained at the third terminal. Protective resistors may be included in the external D.C. to limit the current. Specification 853,947 is referred to.