GB1088910A - Improvements in and relating to indicating apparatus - Google Patents

Abstract

1,088,910. Selective signalling. M. C. PFISTER. July 6, 1965 [Sept. 28, 1964] No. 28645/65. Heading G4H. Apparatus for providing information indicative of the position of, for example, a pointer on a dial of a weighing machine, comprises a cyclically operable scanning device arranged during each cycle to provide an electrical output signal indicative of the position of the pointer, a pulse generating means coupled to the scanning device and arranged to produce a predetermined number of output pulses during each scanning cycle, a counter 34, Fig. 4, arranged to receive output pulses from the pulse generating means during each cycle, a memory device 36 for providing a digital count of the counter 34 and a switch 35 responsive to an output signal from the scanning device upon detection of the position of the pointer to effect the transfer of the contents of the counter 34 to the memory device 36. In the described arrangement, the scanning device comprises a disc 15 rotatably driven by a motor 14, the disc 15 being provided with mirrors 16, 17 which direct light as the disc 15 rotates from a lamp and lens system 19 on to the dial (11), (Fig. 3, not shown), the light being reflected at some stage in the cycle by a reflex reflector 12 on the pointer 10 to actuate a photo-electric device 23 and provide an electric pulse indicative of the position of the pointer. The pulse generating means comprises a further disc 26 which is also rotatably driven by the motor 14 and which is provided with a peripheral series of slots through which light from a lamp 29 is able to actuate a photo-electric device 28 to provide electric pulses in accordance with the rotation of the discs, the disc 26 also being provided with a further slot through which light from a lamp 31 is able to pass to actuate a photo-electric device 32 and provide a reference pulse for each cycle of rotation of the discs. The different pulses are suitably fed to the counter 34 and switch 35 into a circuit comprising gates T 1 to T 4 , bi-stable multivibrators B 1 and B 2 and capacitors 38 so that the memory device is only actuated when the pointer is in a stable position on the dial. The circuit arrangement is such that an indication by the pointer of a tare weight can be compensated for before a measurement of the load is effected.