GB645833A - Improvements relating to measuring apparatus for measuring small movements - Google Patents

Abstract

645,833. Electric indicating systems for small movements. COYLE, M. B., HAYNES, F. G., and METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. March 6, 1947, No. 6360. [Class 40 (i)] In an apparatus for measuring small movements such as the expansion of a metal rod with rise of temperature (Figs. 1, 2, 3), the test-piece movement is transmitted through a quartz push rod 5 and a pressure limiting spring safety device 6 (Fig. 4, not shown), to a slidable plunger 3 coupled through a mechanical amplifying device to rotate over a dial a spindle 4 carrying a bracket 7 on which is pivoted a.pointer 8 carrying an armature 9. The pointer is biassed by spring 10 to normally lie in its plane of rotation, but on periodical energization of electromagnet 11 the armature is attracted towards the dial so that the pointer contact 12 engages a circumferential resistance wire 13, at a position depending on the spindle rotation. The tapped wire is connected as resistance R4 of a Wheatstone bridge (Fig. 5), together with fixed resistances R2, R3, a tapped resistance R1 and a galvanometer 15. R1 is adjusted to balance the bridge for zero movement of the test-piece, and on expansion the bridge balance is re-adjusted automatically by the tapping of R1, which indicates the expansion and may operate a recording device. The tapped resistance wire may take other forms (Figs. 6, 7, not shown), and its variations may operate remote control devices. The apparatus may be actuated by pressure diaphragms or meter pointers. The Provisional Specification refers to the indication of testpiece movements by the unbalance readings of galvanometer 15.