How to distinguish bimetallic thermometer and common glass thermometer?

Bimetallic thermometer is the use of two different metal working in the principle of expansion degree of different temperature changes. Bimetallic thermometer is mainly used in industry of element is one with two or more pieces of metal laminate composed of multilayer metal together. To improve the temperature measuring sensitivity, is usually made of metal spiral coil shape. When multi-layer metal temperature change, the layers of metal expansion or contraction, makes the spiral coil rolled up or let go. As a result of the spiral coil end fixed and the other end connected to a free rotating pointer, therefore, when the bimetallic strip feel the temperature change, Pointers can be on a circular dividing scale to indicate the temperature. This kind of instrument of temperature measurement range is - 50/500℃。 The thermometer and the rod of glass liquid thermometer USES similar, but can be used under the condition of higher mechanical strength. Glass is according to the mercury thermometer, alcohol, toluene, etc liquid has obvious physical properties of heat bilges cold shrink. Glass mercury thermometer consists of temperature measurement package, expansion tubes and parts such as scale, generally speaking, there are internal standard and external standard ( Also called type) Two kinds. Internal standard mercury thermometer scale divided on thin tube expansion behind milky glass. The plate sealed in the glass with bulb protection shell. Usually used for measuring water supply temperature, backwater temperature, economizer exit water temperature, import and export air temperature and air preheater. External standard mercury thermometer has a thick glass tube, rod frame directly on glass tube on the surface, suitable for measuring the temperature of the liquid and gas in the lab. In the expansion of the mercury thermometer thin tube inserted into the two wire, when the temperature reaches the rating, the mercury will lead on, due to the effect of current drive control system, or the device sends out sound and light alarm signal.