Bathroom Scale Tanita – NSL – HA-650

Weighing scales(orweigh scalesorscales) are devices to measureweight．Spring balancesorspring scalescalculateweightthat is the product of mass into gravity (9.807 m/s²) on the force on a spring, whereas a balance or pair of scales using a balance beam compares masses by balancing the weight due to the mass of an object against the weight of one or more known masses. Some of them can be calibrated to read in units of force (weight) such asnewtonsinstead of units of mass such askilograms．使用历史或天平的平衡l balance beam to compare masses may read correctly for mass even if moved to a place with a different non-zero gravitational field strength. Also the spring balances that are designed with reading of weight (force) in mind, would read correctly for weight in a different non-zero gravitational field strength.

Aspring scalemeasures mass by reporting the distance that aspringdeflects under a load. This contrasts to abalance, which compares thetorqueon the arm due to a sample weight to thetorqueon the arm due to a standard reference mass using a horizontallever．Spring scales measureforce, which is thetensionforceof constraint acting on an object, opposing the localforce of gravity.^[6]They are usuallycalibratedso that measured force translates to mass at earth’s gravity. The object to be weighed can be simply hung from the spring or set on a pivot and bearing platform.

In a spring scale, the spring either stretches (as in a hanging scale in the produce department of agrocery store) or compresses (as in a simple bathroom scale). ByHooke’s law, every spring has a proportionality constant that relates how hard it is pulled to how far it stretches. Weighing scales use aspringwith a known spring constant (seeHooke’s law) and measure the displacement of the spring by any variety of mechanisms to produce an estimate of thegravitationalforce applied by the object.^[7]Rack and pinion mechanisms are often used to convert the linear spring motion to a dial reading.