Capillary thermometer is pressure type thermometer. Pressure type thermometer, is based on the sealing temperature measuring system of liquid evaporation changes in the relationship between saturated vapor pressure and temperature, the thermometer for temperature measurement. The principle of capillary thermometer is based on the sealing temperature measuring system of liquid evaporation in saturated vapor pressure and the change of the relationship between temperature, the temperature measurement. Bag when I feel the temperature change when temperature, saturated vapor produced the corresponding pressure in the closed system, cause the change of curvature elastic element, make its produce a shift in the free end, again by the displacement amplification mechanism of gear into the indicated value, the thermometer with a bulb small volume, fast response, high sensitivity and direct reading characteristics, almost set the glass rod thermometer, bimetallic thermometer, all the advantages of the gas pressure thermometer, it can be made into shock, anti-corrosion type, and can realize remote contact signals, heat resistance, 0 10 ma, or 4 20 ma signal. Is currently the most widely use scope, performance is one of the most comprehensive mechanical thermometer table. Capillary thermometer bulb is directly with contact to feel the temperature change of measured medium components, so it has high strength, small expansion coefficient, high thermal conductivity and corrosion resistance and other properties. According to the working material and filling of different measured medium, temperature, package can be produced from copper alloy, steel or stainless steel. Capillary thermometer capillary is to use materials such as copper or steel cold pulling into seamless tube, used to pass the pressure change.