The comparator is a measuring instrument used for linear displacement measurements, oscillations, shape errors, positions and vibrations.
The comparator uses a linear transducer, generally cylindrical in shape, and a display to indicate the displacement of the rod. The end of the rod, called the probe, is in contact with the surface of the object being measured.
The RODER comparators are made with miniaturized indicators and with very low consumption, so that they can be easily powered by a common button battery. The displays of the comparators are normally made with a resolution of 0,01 mm (centesimal), 0,001 mm (millesimal). Some special models of comparators can even reach resolutions below one micron.