TABLE OF CONTENTS Calibrating displacement measuring equipment usually takes place at two levels. The first level is the traditional metrology laboratory that calibrates working level devices used on a daily basis in machine shops and assembly and production facilities. These laboratories also make dimensional measurements on items produced by the production facility or on items tested in a laboratory. The second level is the use of metrology laboratory equipment to calibrate displacement transducer systems. These calibrations typically provide the static response of the sensor as a function of distance or displacement.
The basic metrology laboratory standards are artifact standards that are made in a variety of shapes and sizes with very precise dimensions. They can be blocks with two parallel faces, cylindrical plugs or pins with precise outside diameters, rings with precise inside diameters, and thread gauges to match screw or pipe threads. Other standards that actually measure dimensions include micrometers, dial indicators, calipers, and height gauges. These standards are all subject to error because of to the thermal expansion coefficient of the material from which they are made. The universal reference temperature for dimensional measurements is 68 F or 20 C. Metrology laboratories are maintained at this temperature, and any equipment or pieces to be measured are stabilized at this temperature before they are measured.
Other equipment used in metrology laboratories includes coordinate measuring machines (CMM) and laser-based measuring equipment.
The coordinate measuring machine is comprised of a solid reference base on which the part to be measured is mounted and a three-dimensional...
