What factors affect the performance of a Vickers hardness tester?

Taiwan Nakazawa answers for you, regulations regarding ball indenters:
(1) The steel ball diameter must be selected according to regulations. Brinell hardness values obtained under different steel ball diameter conditions vary from each other and cannot be compared.
(2) The Vickers hardness of the steel ball should be no less than 850HV10, and the Vickers hardness of the cemented carbide ball should be no less than 1500HV10.
(3) The surface roughness Ra of the steel ball should be no greater than 0.04μm. Regarding the steel ball: besides the ball diameter, the Vickers hardness value is also related to the ball hardness and ball surface roughness, etc.
Regarding the specimen: the Vickers hardness value is related to the specimen material, specimen shape, specimen surface roughness, and specimen temperature, etc.