GB568676A - Improvements in or relating to instruments for measuring and indicating variables - Google Patents

Abstract

568,676. Meters; indicating-apparatus. FOSTER INSTRUMENT CO., Ltd., and FOSTER, C. E. March 26, 1943, No. 4926. [Class 106 (iv)] [Also in Group XXXVI] The invention relates to instruments of the type in which an unknown variable to be measured is opposed to a known variable, adjustable at will, a scale being positioned according to the value of the known variable, and a pointer according to the degree of out-of-balance of said two variables, whereby the relative positions of said pointer and scale indicates the value of the unknown variable. In Fig. 1, the potential developed by a pyrometer 1 is opposed by a potentiometer 3, secured to a scale 9, rotatable by rack-and-pinion mechanism, Fig. 4, to vary the value of the potentiometer resistance tapped off by a fixed slide 5. If the potentials of the pyrometer and the potentiometer are balanced or nearly so, the needle 7 of a galvanometer comes within a beam of light projected through an opening on to a screen to indicate on the magnified image of part of the movable scale 9 the temperature corresponding to the potential developed by the pyrometer. The plate 14 may carry stops for the needle 7 with coloured patches adjacent the stops to indicate the limits between which the needle must lie for accurate indications. The invention is also applicable to the measurement of resistance (Fig. 2, not shown) employing a ratiometer, or (Fig. 3, not shown) employing a Wheatstone bridge.