Leeb Rebound Principle

The portable hardness testers used most commonly for metals are based on the Leeb rebound method invented by Proceq scientist Dietmar Leeb in the 1970s.
 
The Equotip Piccolo 2 / Bambino 2 operate according to the Leeb principle, in which the hardness value is calculated from comparing the energy of a test body before and after impacting on a sample. This Energy QUOtient (EQUO) is quoted in the hardness unit HL and is calculated from comparing the impact and rebound velocities (vi , vr) of the impact body. It rebounds faster from harder samples than from softer ones, resulting in a greater energy quotient which is defined as 1000·vr/vi.