The structural design of the instrument

(1) Plastic casing(with related equipment excluded): plastic casing should be of fairly good thermal stability, and the working temperature of materials is required to behigher than the maximum temperature of equipment casing. The plastic casing is made of fire-resistant materials and inflammation-resistant materials.

(2) Light metal casing-the total content of aluminum, titanium, magnesium is required to be no more than 15%; for the instrument of category II, the content of magnesium is required to be no more than 6%。