GB973996A - Means for imparting angular movement to an indicator or rotor - Google Patents

Abstract

973, 996. Frequency measurement; electric measuring instruments. JOSEPH LUCAS (INDUSTRIES) Ltd. Dec. 2, 1960 [Dec. 2, 1959], No. 40919/59. Headings G1Q and G1U. [Also in Division H2] An arrangement for imparting an angular movement to a rotor 9 comprises a transistor 10, a means for applying intermittent pulses of one polarity to the base of the transitor, a first winding 5 connected between the collector of the transistor and a D.C. source 11 of the same polarity as the pulses, a second winding 6 connected between the transistor base and a D.C. source of opposite polarity, which is also connected to the emitter, a common core 4 on which the first and second windings are wound, a third winding 8 and a diode 13 connected in series across the first winding, a second core 7 on which the third winding is wound, the second core being spaced from the common core, and an angularly moveable induction disc 9 so arranged in relation to the cores that angular movement will be imparted thereto by the interaction of the flux produced by the second and third windings after the transistor has been cut off. The system may be used in one application for measuring the angular velocity of a rotating part, i.e. as a speedometer or tachometer, the part being used for example to operate a cam operated contact breaker 14 to supply pulses to the transistor base. The pulse on the base causes the transistor to conduct, and the current increases cumulatively by regenerative action between the windings 5 and 6 until the winding 5 is saturated, after which, because no voltage is induced in the winding 6, the transistor cuts off, causing a current to flow through the diode 13 and the winding 8. Thus the flux in the winding 8 increases as that in the winding 5 falls. These changes exert a torque on the disc 9, moving it against a spring. The average torque will depend on the pulse frequency, so that by suitable calibration the instrument can be used as a tachometer or speedometer. Alternatively, by applying the pulses through a rectifier from a source of alternating current the instrument can be used as a frequency meter. If the spring is omitted the instrument may be used as a low torque D.C. motor rotatable at an angular velocity proportional to the frequency of the pulses applied to the base of the transistor. Either a PNP or NPN transistor may be used, with appropriate supplies.