Measuring Scales

Scales are either spring or balance scales. Spring scales are the kind sold for ordinary household use. At the top is a flat pan upon which the article to be weighed is placed. This pan rests upon a coiled wire spring, which is contained in the iron box beneath. A pointer connected with the spring operates over a dial which may be either upright or tilted backwards. The contraction and expansion of the spring with the weight of the article on the pan cause the pointer to move. Some of these scales are provided with tinned scoops; others have an extra "tare" hand which gives the weight of the container separately from the article. Although spring scales are satisfactory enough for household use, they are not accurate enough for trade use, because the force of the spring varies, contracting and expanding with changes in the temperature.

There is a variation of the spring scale on which the article to be weighed is hung from a hook attached to the end of the coiled spring. The spring moves a pointer over an indicator.

For accurate weighing platform scales are used. In this style a small known weight at one end of a beam is made to balance a heavy unknown weight at the other end, on the lever principle.