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).
ELKA
The first model, the ELKA 6521, was introduced in 1965, and used germanium transistors and a nixie tube display. It weighed 8.5 kg and was allegedly the first calculator in the world to include a square root function. Its developers – Lyubomir Antonov, Petar Popov and Stefan Angelov, were the first scientists in the field of electronics to win the highest honour in Bulgaria at the time, the Order of Georgi Dimitrov.