Patent GB-365284-A (GB)
Title: Improvements in or relating to measuring instruments
IPC: G01R13/08
Filed: 1930-12-22
Abstract: 365,284. Measuring - instruments. BROWN INSTRUMENT CO., Wayne Avenue, Philadelphia, U.S.A.-(Assignees of Harrison, T. R. ; Wyncote, Pennsylvania, U.S.A.) Dec. 22, 1930, No. 38586. Convention date, Jan. 24. [Class 118 (ii).] Relay devices.-An instrument with a pointer or marking element movable over an exhibiting surface, such as a graduated scale or recording chart, is provided with compensating means for preserving the relative position of the element and surface during variations in the dimensions of the exhibiting surface due to changes such as humidity and temperature, in the conditions of the surrounding atmosphere. As shown applied to an electrical measuring instrument with a recording device the value being measured imparts, by any known means, a movement to a screwed shaft B, Figs. 1 and 1a, varying in magnitude and direction with the value. On the shaft B is mounted a plate F<1> with ears F2 and a spring finger F<4> fitting into the spiral groove of the shaft. The free end of the plate F<1> is divided into a plurality of tongues F<7> F8, F9. Supported on the central tongue F<8> is the horizontal arm C<1> of a yoke plate C<2> mounted on the shaft B within the ears of the plate F<1>. The free end of the arm C<1> carries a marking member C<4>. The record-sheet D passes over a clock-driven roll E having pins engaging holes and slots D<1>, D<2> at opposite sides of the sheet. Abutting one side of the sheet is a spring - controlled disc E<5> with a reduced portion E<6>, Fig. 2, upon which the sheet is held by a roller E<7> on a spring arm E<8>. Variations in the width of the chart due to changing conditions of the atmosphere are communicated to the disc E<5>. The movement of the disc through a spring - controlled bell crank G<1> pivoted on a bracket A<2> is transmitted to a bar H pivoted to the bell crank and supported at its opposite end to a bracket A3. The bar passes between the tongue F<8> and tongues F', F<9> and due to its angular movement about the pivot H<1> imposes a correction on the plate F<1> and marking element C4. In a modified construction shown in Fig. 3, the disc F<5> is replaced by a spring-controlled disc J forming a continuation of the roll E and having pins J engaging the slots in the record-sheet. Longitudinal movement of the disc is permitted by means of pins J<2> on the roll E engaging corresponding apertures J<3> in the disc. An embodiment of the invention as applied to a recording potentiometer working on the " null " or compensation method is shown in Fig. 4. The circuit arrangements include a thermocouple L, galvanometer L\ switch L<2>, standard cell L<3> operating dry cell L<4>, rheostat L5, resistances L<6>, L<8> and slide wire resistance L<7> with contact L<9>. The standard cell circuit is modified by the addition of a resistance K<3> mounted on an insulated arm K<5>. This resistance is adapted to be varied by means of an arm K co-operating with the disc J longitudinally movable against spring action by the dimensional changes in the record-sheet due to variations in the atmospheric conditions. The movement of the contact L<9> to effect a balance is utilized to operate the shaft B carrying the marker C<4>.