What is a triple beam balance?

A triple beam balance is a type of scale commonly used in the laboratory to determine the mass (by weight comparison) of samples. To use the balance, you use sliding weights called riders on three beams, each with progressively small incremental amounts.

Familiar versions of the concept are seen in sliding bar postal scales, and in the older scales used in doctors' offices (which similarly have multiple beams).

The larger increments may be 100 grams and 10 grams, and the final beam will display in grams and decimal fractions of a gram.