GB722713A - Improvements in weighing machines - Google Patents

Abstract

722,713. Electric dynamometer. HEENAN & FROUDE, Ltd. Nov. 24, 1952 [Nov. 22, 1951], No. 27381/51. Class 40 (1) An absorption dynamometer D (Fig. 1) measures torque by controlling the current in a coil c attached to the end of an arm A rotating with the dynamometer drum, by varying the capacity between two plates F, M, one of which F is fixed, and the other M is attached to the arm A, the current in the coil c being measured by the force exerted on a spring- loaded armature S<SP>1</SP> attached to a spring balance S. The system is initially balanced with full exciting current in the coil c. Movement of the arm A due to an applied torque decreases the capacity between the plates M, F, thereby increasing the voltage fed by a crystal-controlled oscillator V 1 , V 2 (Fig. 3) to a balanced amplifier V 3 -V 5 , the double triode output valve V, controlling the grid-cathode relationship of a thyratron V., whereby the nett current through coil c is reduced, to compensate for the applied torque, and is indicated on the spring balance S: Damping is produced mechanically by a dashpot D', and electrically by a pick-up coil F'. To increase the range, the torque to be measured may be partly counterbalanced by weights D<SP>1</SP>.