The Mitutoyo 209 series Digimatic internal tube thickness caliper gauge has a combination analog/digital LCD display and large measuring depth for taking inside dimension (ID) measurements of hole diameters, thickness of grooves or tubes, and other hard-to-reach internal dimensions.

Depending on the model, these units may come with either ball contact points suitable for measuring internal wall thickness of tubes, or disc contact points suitable for measuring flat surfaces. The calipers have an Ingress Protection 67 (IP67) rating, which ensures that components are resistant to debris and to submersion in liquid under standard conditions for up to 30 minutes. At minimum, functions include zero-set, preset, automatic power off, inch/metric, and conversion data hold. An output port transmits results to a Mitutoyo miniprocessor or computer for statistical process control (SPC) through an interface cable (sold separately). The unit comes with, and is powered by, a single AA battery that lasts approximately 350 hours with continuous normal use.

Calipers measure the distance between two opposing sides of an object. They make inside, outside, depth, or step measurements, according to their type. Calipers are commonly used in architecture, metalworking, mechanical engineering, and machining. The simplest calipers have two legs to mark the two points and require a ruler to take the measurement. More complex calipers use two sets of jaws instead of legs and have up to two graduated scales. Vernier, dial, and digital calipers give direct and accurate readings and are functionally identical, having a calibrated scale with a fixed jaw, and another jaw with a movable pointer that slides along the scale. The vernier caliper has a scale sliding parallel to the main scale for an additional, fractional reading to improve measurement precision. The dial caliper has a circular dial with a pointer on a toothed gear rack replacing the second vernier scale. As with the vernier, this second measurement is added to the reading from the main scale to obtain the result. The digital caliper takes a differential by zeroing the display at any point along the slide, with an LCD that displays a single value in English and/or metric units.

Mitutoyo manufactures precision measuring tools, metrology equipment, and systems. The company was founded in Tokyo in 1934 and formed Mitutoyo America Corporation in 1963, which is headquartered in Aurora, IL.