ITF

17 v. Rebound. Record four valid measurements per ball (disregarding bounces that deviate significantly from vertical) and report mean rebound height in centimetres to one decimal place. vi. Internal pressure. a. Packaging. All sealed packaging is measured using a standard pressure gauge with needle attachment and rubber seal. b. Ball. Four balls are tested. Measurements are taken using a standard pressure gauge with needle attachment. Note: this test does not apply to Stage 2 and Stage 3 balls. vii. Durability. Select six balls at random from the sample that was tested for approval. Apply the wearing regime described in Section 1.3. Visually inspect the balls for signs of detachment of the fabric cover, and cracks or ruptures. Record the results for mass, size, deformation and rebound, as described in paragraphs (i) to (v) above. Report the change in the specified properties from the original results for each test. Note: this test does not apply to Stage 1, Stage 2 and Stage 3 balls. 1.5 Calibration The apparatus used for the various tests must be regularly checked for accuracy of calibration as follows: Size. The ring gauges should be checked for accuracy against a known traceable reference every two years. The tolerance on ring gauge diameter should be ± 0.0064 cm (0.0025 inches). Size (Durability). The drop gauge should be checked monthly with calibrated slip gauges. The accuracy of the drop gauge should be ± 0.002 cm. Mass. The weighing scales should be checked with calibration weights monthly. The accuracy of the scales should be ± 0.01 g. Rebound. Where the 'video' system is used for measuring rebound, the horizontal alignment of the light beam must be checked at the beginning and end of each test sequence. The accuracy of drop height and the frosted and transparent scales should be checked monthly. The accuracy of the drop height and both scales should be ± 0.3 cm (0.1 inches). Pressure. Pressure gauges should be checked for accuracy annually. The accuracy of the gauges should be ± 0.3 kPa (0.04 psi). Deformation. The Stevens machine should be checked daily for beam balance with the contact weight removed. It should be checked also for accuracy of platen

• Cover