The New International Encyclopædia/Spring Balance

SPRING BALANCE. An instrument used to determine the weight of a body by the extension or compression of a spring. In the usual form of spring balance a spring of coiled wire is contained in a metal case and incloses a central rod to which is attached at one end a hook, and at the other a projection which extends through a slit in the case and moves over a graduated scale. The central rod can also be connected by means of a rack and toothed wheel with an axle on which is fastened a pointer moving over a circular scale or dial. The spring balance measures the amount of attraction of the earth at any particular place; consequently, readings at the equator would be different from those at the poles or other places on the earth's surface. The ordinary balance, on the other hand, would give the weight for a body irrespective of its position. The force of the spring varies with temperature, which alters the length and elasticity of the wire and renders impossible precise measurements.