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).
Weighing scale
These scales are used in the modern bakery, grocery, delicatessen, seafood, meat, produce and other perishable goods departments. Supermarket scales can print labels and receipts, mark mass and count, unit price, total price and in some cases tare. Some modern supermarket scales print an RFID tag that can be used to track the item for tampering or returns. In most cases, these types of scales have a sealed calibration so that the reading on the display is correct and cannot be tampered with. In the USA, the scales are certified by the National Type Evaluation Program (NTEP), in South Africa by the South African Bureau of Standards and in the UK by the International Organization of Legal Metrology.