GB762499A - Improvements in or relating to electronic measuring apparatus - Google Patents

Abstract

762,499. Selective signalling by counting impulses. BRITISH TABULATING MACHINE CO., Ltd. Oct. 22, 1954 [Nov. 30, 1953], No. 33174/53. Class 40 (1). [Also in Group XL (b)] A shaft, e.g. of a weighing machine, signals its position by sending impulses to a counter which is stepped in one direction for clockwise and in the other for counter-clockwise rotation of the shaft. Discrimination between the two directions is obtained by causing the shaft to generate two sets of impulses in quadrature, deriving from one set two trains of impulses corresponding respectively to dark-to-light and light-to-dark transitions and rendering one or other train effective to control a trigger-circuit in accordance with the position of its impulses in relation to the impulses of the other set. As shown, the shaft carries a disc with two rings of alternate opaque and transparent portions cooperating with a lamp and with photo-cells 1, 2 arranged on a radius. It will be seen that when the disc rotates clockwise, the light-to-dark transitions of cell 1 take place with cell 2 light and conversely, when the disc moves counterclockwise, the dark-to-light transitions. The same effect can be produced with a single obturating ring and the photo-cells staggered. The counter is a set of polycathode discharge tubes. Discriminating arrangement. Each lightto-dark transition of cell 1 is made to produce a short + impulse in line 17 and each dark-tolight transition a short + impulse in line 18. Each transition either way of cell 2 produces an impulse in line 19 and these impulses control a bi-stable circuit 5 so that it is in one state while cell 2 is light and opens gates 6 and 7 and in the other when cell 2 is dark. Accordingly, with gates 6, 7 open, impulses reach the trigger circuit 8 via line 20 or line 21 according as the rotation is clockwise or counter-clockwise. Circuit 8 determines whether gate 9 or gate 10 shall be open in readiness for an impulse from 5 at each light-to-dark transition of cell 2. An impulse is thus sent for each pair of opaque and transparent scale marks to line 24 for clockwise and to line 25 for counter-clockwise rotation. Counter circuit. Impulses on 24 and 25 operate the polycathode units counter 53 in one direction or the other in known manner. When the discharge passes to electrode 0, the lefthand half of a valve pair 50 conducts and the right-hand half is cut off. A negative impulse is passed on to the left-hand half of a pair 52 to to cause the right-hand half to conduct provided that the equipment is set for adding as determined by the bias voltage on 22 furnished by the trigger 8. An " add " impulse is then given to the tens polycathode tube 54. If the equipment is subtracting, the cessation of the discharge to electrode 0 changes over the pair 50 and the resulting impulse causes a discharge in the right-hand half of 51 provided that the trigger 8 is biasing it to " subtract". A " subtract "-impulse is then given to the tens tube.