How to check standard mercury thermometer?

Standard mercury thermometer is made of liquid mercury as fill glass rod thermometer, the index value of 0. 5 ℃ or 0. 1℃。 As temperature measurement by dry mercury substance has a higher accuracy compared with other substances, so commonly used as a standard equipment, check some other industrial thermometer, bimetallic thermometer for example, it can also be used as precision thermometer. Why to verification standard mercury thermometer? Instrument to tell everyone: in the process of production, calibration bimetallic thermometer thermometer is an important work in process, in order to the accuracy of the calibration, the requirement is very important to the accuracy of the standard mercury thermometer, so every two years a standard mercury thermometer must be sent to the professional technical center verification, have issued by the national testing center of metrology verification certificate before it can be applied to the production of calibration bimetallic thermometer.