# Force standard measurement

Question: What is the standard of force?
I don't mean the Newton.
We can say that an atomic watch is the standard way of measuring time.
What is the standard way of measuring force?

As you know the SI unit of force is the newton (N), and is defined as the force required to accelerate a mass of 1 kg at a rate of 1 ms-2.

In practice it is not convenient to create an acceleration of one metre per second per second on an object having a mass of one kilogram in order to produce the standard of force of one newton. Instead, to produce a calibration for the unit of force, laboratories use known masses (deadweights) which will produce a known force when subjected to the effect of the local acceleration due to gravity. Machines which generate force in this way are called deadweight machines. The forces are measured using transducers.

In the UK the National Physical laboratory (NPL) has a number of force machines providing UK standards in the range from 1.5 N to 30 MN. The forces from 1.5 N to 1.2 MN are produced using deadweights and the higher forces are generated by using hydraulic machines. With these machines, NPL provides a calibration service to industry for force transducers and strain cylinders.

These machines are also calibrated themselves and compared with similar machines in other countries.

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