mechanical balance
Quick Summary
A mechanical balance is an instrument used to compare the weights of two objects, primarily to determine differences in mass. The earliest forms date back to ancient Egypt, with improvements by the Romans and the development of modern mechanical balances in the 18th century with the invention of knife-edges.
A typical mechanical balance features a rigid beam that pivots on a central knife-edge. Pans for holding the objects to be weighed are suspended from the ends of the beam. The deflection of the beam, indicating the weight difference, can be shown by a pointer on a scale or a mirror reflection.
There are various methods for using a balance, including direct weighing and the substitution method, which can correct for unequal arm lengths. Specialized types like microbalances and ultramicrobalances are designed for weighing extremely small masses, often utilizing principles of elasticity and torsion. While electronic balances are now more common and accurate, mechanical balances were once highly precise measuring devices.1
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