The HT-1000A and HT-2000A hardness testers operate on the Leeb principle, a dynamic hardness test method based on velocity measurement. They include a guide tube and an impact body. The impact body contains a magnet and tungsten-carbide ball, measurements are performed using a spring to propel an impact body through a guide tube towards the test surface. When the ball is within 1 mm of the part’s surface, the magnet induces a voltage into a coil surrounding the guide tube. After penetration, the impact body rebounds and the magnet returns through the coil inducing a second voltage. Both voltages are proportional to the velocity of the impact body.
Leeb hardness value (HL) is determined using the following formula: HL = (Vb/Va) x 1000
Where Vb is the rebound velocity of impact body and Va is the impact velocity of impact body.