In the package plate making industry, three kinds of measuring equipment are basically required, that is ultrasonic hardness tester, surface roughness tester and coating thickness gauge. As is known to all, copper plating and chrome plating are two essential processes of plate making. Firstly, there is hardness requirement both for the copper plating and chrome plating. Thus a digital ultrasonic hardness tester is needed to check their hardness in the factory. Secondly, a surface roughness tester is required to make sure the surface of the plate roller is qualified for engraving. Finally, the thickness of copper plating or chrome coating should also reach the requirement of processing. So coating thickness gauge is also a must-have tool for plate making factories.