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an instrument for measuring the depth of openings, grooves, recesses, and so on. The depth gauge uses as its base the surface from which the measurement is to be made. According to the type of reading device, depth gauges are classified as height-and-depth gauges, with a measurement range from 0 to 200 or 320 mm and calibrations of 0.05 mm, or with a measurement range from 0 to 500 mm and calibrations of 0.1 mm; micrometric depth gauges, with a measurement range up to 150 mm and calibrations of 0.01 mm; and indicator depth gauges, with a measurement range of 100 mm and calibrations of 0.01 mm.
Height-and-depth gauges with flat measuring rods have become widespread. Some of them have rods with an offset at the end—for example, for measuring the thickness of a groove—or rods in the form of cylinders 2 mm in diameter for measuring depths in hard-to-reach places. On height-and-depth gauges the dimension is marked off directly on a scaled ruler; micrometric and indicator depth gauges have replaceable measuring rods whose indications are read from a micrometer with a range of measurement of up to 25 mm or from an indicator with a range of measurement of 10 mm respectively.
N. N. MARKOV