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
Z scale is one of the smallest commercially available model railway scales (1:220), with a track gauge of . Introduced by Märklin in 1972, Z scale trains operate on 0–10 volts DC and offer the same operating characteristics as all other two-rail, direct-current, analog model railways. Locomotives can be fitted with digital decoders for independent control. Model trains, track, structures, and human/animal figures are readily available in European, North American, and Japanese styles from a variety of manufacturers.