Weighing scale
The balance (also balance scale, beam balance and laboratory balance) was the first mass measuring instrument invented. In its traditional form, it consists of a pivoted horizontal lever with arms of equal lengththe beamand a weighing pan suspended from each arm (hence the plural name ""scales" for a weighing instrument). The unknown mass is placed in one pan and standard masses are added to the other pan until the beam is as close to equilibrium as possible. In precision balances, a more accurate determination of the mass is given by the position of a sliding mass moved along a graduated scale. Technically, a balance compares weight rather than mass, but, in a given gravitational field (such as Earth's gravity), the weight of an object is proportional to its mass, so the standard masses used with balances are usually labeled in units of mass (e.g. g or kg).
Z scale
The first attempts to use digital system in Z scale were based on NEM standard, Selectrix, which offered the smallest decoders in the market, with thicknesses of less than 2 mm. German company Müt brought also the first digital control central unit designed specially for Z scale in the market in the early 2000s. Use of the popular National Model Railroad Association (NMRA) Digital Command Control (DCC) standard has expanded substantially in Z scale recently as locomotive decoders with sizes comparable to the sizes of smallest Selectrix decoders have become available.