In practice, we need to have standards available over a range of forces, and this has been done by designing what are known as 'dead weight machines', one of which is at SP in Borås. Using ingenious mechanical mechanisms, our machine can generate accurate forces over the range 250 – 1000000 N.
In the range up to 100 kN, the machine employs the direct force generated by the mass, while for higher forces up to 1 MN, the force is generated by a mechanical system of levers that magnifies the direct force by a factor of ten. In the lower measurement range, the relative error of the force is 0,005 %, while in the higher range it is 0,01 %. Relative repeatability and reversibility of the force generated by the machine are in the range 0,002 – 0,005 %.
The dead weight machine is installed in a temperature-controlled area, in which the ambient temperature is maintained constant at +20 °C.