The Leeb Hardness TKM359CE operation principle is the dynamic method of hardness control. The hardness measurement procedure is: 1) Install the probe normally to the surface of the test subject. 2) By pressing the probe housing, "advanced" the probe- bring it into the working state. 3) Press the release button on the probe. 4) The hardness measurement results will appear on the tester display in 1 second approximately.