comparator microscope

com·par·a·tor mi·cro·scope

obsolete device constructed with one or more microscopes having micrometer eyepieces used to measure dimensional changes during setting or temperature changes. Similar devices continue use in labels for urine testing.
References in periodicals archive ?
CCD camera of the precise length comparator microscope for determining the dash position of length measures is a source of temperature calibration errors having an essential impact on calibration process precision.