A spring balance measures the weight of an object by opposing the force of gravity acting with the force of an extending spring.
It is used to determine mass as well as weight by recalibrating the scale.
It works by Hooke’s law, which states that the force needed to extend a spring is proportional to the distance that spring is extended from its rest position.
Some spring balances are available in gram or kilogram markings and are used to measure the mass of an object.
Spring balances consist of a cylindrical tube with a spring inside. One end (at the top) is fixed to an adjuster which can be used to calibrate the device. The other end is attached to a hook on which you can hang masses etc.