Spring balances are a familiar sight in the classroom; they are commonly used to measure the force exerted on an object. This force is usually measured in Newtons and is essentially the weight of an object. The weight of an object is a measurement of its mass x gravity (w=mg).
Spring balances are also sometimes known as Newtonmeters for this reason.
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 (the top) is usually 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. As masses are added, the spring stretches and the resultant force can be read from the scale.
The traditional spring balance has been adapted in some models to measure a pushing force. Instead of the spring being stretched, a compression spring is used. In these devices, the balance is held firmly and the free end pushed against an object (eg a trolley). It is read in the same way as a traditional spring balance.
Many types of spring balance are available through lab suppliers. The more robust models tend to be the cylindrical types however many models are prone to overextension of the spring mechanism by pupils. Choosing a model which does not allow the spring to be overstretched will increase its lifespan.
Ensure spring balances are calibrated to read 0N when no masses are attached before use.