Prototype of Depth Standard for Elastomer Hardness Tester

National Institute of Metrology (Thailand) has fabricated the prototype of depth standard to calibrate the depth of indentation for elastomer hardness tester according to ISO 18898, ASTM D2240 and ASTM D1415. It was designed as a displacement device consisting a linear scale inside which can measure the indentation-depth covered the measuring range from 0-2.5 mm. The depth standard can acquire the value of indentation depth in accordance with the scale of elastomer hardness tester indicated from 100 shore to 0 shore in steps. The calibration for the prototype of depth standard was carried out by a set of gauge blocks. The accuracy of the prototype was within ±1 µm which met the requirement according to ISO and ASTM standard. Then, the depth standard was used as a part of the indentation-depth measuring system. The calibration stand which was the other part of the indentation-depth measuring system was investigated as a problem issue due to the stand deformation during the indentation depth calibration. NIMT solved the problem by installing another laser measuring device to compensate the movement of elastomer hardness tester due to the deformation of stand. This paper also pointed out the use with a caution of depth calibration procedure by gauge blocks according to ASTM D2240. (paper)