The commonly used method and characteristics of thermometer

According to the way of measuring temperature of the thermometer can be divided into two categories, contact and non-contact measuring temperature method. Any two objects of different degree of cold and hot contact, is bound to produce heat transfer phenomenon, quantity of heat, high degree of heat by the object to the low degree of heat, until the degree of hotness or coldness of two objects are consistent to reach thermal equilibrium condition. So can choose objects of a certain physical quantities, Such as the volume of a liquid, the resistance of the conductor, etc. ) The nature of the change with temperature, it is concluded that the temperature of the object to be tested. Measurement of physical properties of the object, must be continuous and single value changing with temperature, better repeatability. Common thermometer for the contact method of measurement are expanding body thermometer, pressure type thermometer, bimetallic thermometer, thermal resistance, thermocouple, etc. Their characteristic is simple, reliable, high precision, has the lag, the movement of solid measurement difficulties, temperature measurement components easily damaged, the temperature field with the object being measured medium produces chemical reaction, temperature limit restricted by high temperature resistant material. Non-contact method of temperature measurement, temperature measurement device is not in direct contact with the object to be tested, it is to use the object or thermal radiation for measuring temperature, the temperature measurement range, in principle is not limited by temperature limit, responsive, no lag, don't destroy the temperature field of the object to be tested, but the object emissivity, smoke, steam, distance and other factors, the temperature measurement error is bigger.