SLQ-300B Horizontal instrument zero calibration is based JJF1084-2002 square levels and strip test level calibration specification requirements of the design can be used to calibrate the level of cooperation as meter, square levels, of the test level of zero error, with accuracy high stability, easy operation. The main technical indicators (1) Measuring range: 150-300mm Article type level; 300 × 300mm and below the size of square levels. (2) adjust the zero table flatness: 330 × 100mm flat zero order requirements. (3) the accuracy of the parallel flat feet: flatness 0.6μm / 300mm; Parallelism 1μm / 300mm. (4) the accuracy of the mandrel: garden taper 1μm / ф36 × 300mm. Measurement variability (5) of the machine: 2μm / m. (6) Volume: 500 × 200 × 240mm. (7) Weight: 32kg. Third, the instrument consists of: consists of (1) Feet (2) of the base (3) zero bit table (4) parallel flat feet (5) semi-cylindrical backer rod (6) flat mandrel (7) positioning block