Regulation 54
In testing any weight, the inspector shall—
(a)
place the appropriate local or working standard on one pan of his testing equipment; and
(b)
place counterpoises on the other pan so that the pointer exactly indicates zero; and
(c)
replace the standard by the weight under test; and
(d)
if the pointer does not then exactly indicate zero, add sufficient testing counterpoises to either pan to determine whether the weight falls within the prescribed limits of error:
provided that where in any particular case the inspector is of the opinion that it is not practicable to adopt such procedure, he shall test the weight by direct comparison with the appropriate local or working standard.