The main component of chocolate is cocoa butter. Cocoa butter is polymorphic and thus can exist in different crystal forms. These crystal forms are created when chocolate is cooled. The crystal form in which cocoa butter mainly crystallizes determines the properties of the chocolate.
The type V crystals in particular provide a pleasant hardness, a glossy solid texture and a typical hollow sound when broken. Tempering is the process of obtaining these stable Beta V crystals. The temper meter measures the quality of the tempering, and is therefore the most important measurement that should characterize chocolate.