General Care of Metrological Equipment (Metrology)

1.8.
The equipment (apparatus) used for precision measurements is designed to fine limits of
accuracy and is easily liable to be damaged by even-slight mishandling and such damage may not
be noticeable. A great deal of careful handling is, therefore, required. As far as possible, the highly
finished surfaces should not be touched by hand because the natural acids on the skin are likely to
corrode the finished surface and also the temperature of body may upset the dimensions of the
precision instruments. In order to overcome this many standard metrology laboratories recommend
washing of hands thoroughly and coating them with a thin film of pure petroleum jelly before
handling the instruments. Further very precise equipment like slip gauges is allowed to be handled
only by using a piece of chamois leather or tongs made from a strip of “Perspex”.
When the equipment is not in use, it should be protected from atmospheric corrosion. For
this purpose, the highly finished surfaces are first wiped with a solvent to remove any finger marks
and then coated with mixture of heated petroleum jelly and petrol. This mixture spreads much more
easily and is applied with cloth or with fingers. Brushing is not recommended as it is liable to trap
air which, with the moisture it contains, may cause rusting.
As the standard temperature for measurement is 20°C, for very precise measurements the
instruments and workpieces should be allowed to attain this temperature before use and the
handling should be as little as possible.