GB560012A - Improvements in or relating to means for reading the indication of measuring instruments - Google Patents

Abstract

560,012. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd., and HARTLEY, G. C. Sept. 12, 1942, No. 12853. [Class 40 (i)] [Also in Group XIX] The position of the pointer of an instrument such as a voltmeter or micro-ammeter is determined by the passage of a spark between an electrode carried by the pointer and one of a series of fixed electrodes, thereby ionising a cold-cathode discharge tube. As shown in Figs. 1, 2, the pointer N carries on the end of a glass filament I a U-shaped electrode BR of which the limbs co-operate with a feeder ring FR and segmental electrodes V ... Y, the latter being connected to discharge tubes A ... D. The opening of a switch S applies a high voltage to the feeder ring FR from a spark coil TR so that a spark jumps the gaps and ionises the appropriate discharge tube, operating an anode relay AA ... DD. The tube is extinguished by means of a relay contact Z. In Fig. 3, a single discharge tube A is connected to the segmental electrodes in turn by a rotary switch U, which is stepped by impulses received by a relay IP until the position of the pointer N is found, when the operation of the anode relay AA stops the switch. The relay IP also controls the spark coil TR. The stepping impulses may come from a distant station to which the position assumed by the switch U may be signalled in known manner. Alternatively, the spark coil TR may be arranged to provide sparks at regular intervals for checking the position of the pointer.