The MS Instruments PLC Barrel Straightness Gauge is a device used to measure the straightness of a barrel or tube at multiple positions along its length. The system comprises the laser and target assemblies along with a charger and a data-logging unit. This latter device comes in two forms: A standalone simple display of target positions or a Notebook PC unit.

A low-power eye-safe laser with integral rechargeable battery is inserted into a collar matching the internal dimensions of the tube. The laser is then inserted into the barrel and positioned at the base of the barrel. Insertion and removal of the assembly is by simple screw-in rods.  The target assembly is inserted into the barrel in a similar manner to the laser assembly, and may be moved along the length of the barrel to analyze the straightness along the length.