Superficial Rockwell Hardness Tester/Superficial Hardness. Model No. 900-420. Features. Reading in all Superficial Rockwell Hardness scales such as HRN & HRT, as well as Automatic conversions to Brinell HB and Vickers HV. Touch Screen selectable system. Upper/Lower Limit Settings. . Features: Model No. 900-420 Superficial Rockwell Hardness. Tester. This digital Superficial Rockwell hardness tester with fully automated load/unload procedures affords highly sensitive and accurate readings. Micro computer controlled Touch Screen with USB output to flash drive. Utilizing the guidelines of ASTM E-18, the 900-420 digital Superficial Rockwell hardness tester. offers programmable scale conversions, dwell times, statistical capabilities and test counter. Capable of testing in all of the Superficial Rockwell hardness scales. For full conformance to the latest E18-20 specification, please call 201 962-7373. Direct Loading Method With Load-Cell Instead Of Dead Weight System. High Speed Test Cycle and Extremely Accurate Loading Control. . Automatic conversions to HB, HV, Superficial Rockwell Scales. Touch Screen selectable system. Upper/Lower Limit Settings. Test resolution: 0.01HR Rockwell unit;. Operation temperature:50Deg. – 95Deg. F 10 Degrees C – 35 Degrees C. Ambient environment: clean, no vibration, no strong magnetic field, and no corrosive medium;. Power supply:single phase, AC, 110-220 with manual change, 50 – 60Hz, 4A;