Thermocouple and the thermocouple, are we often can see the temperature of the instrument at ordinary times, both in industry application is very extensive. When measuring temperature, however, need to know if the measured object under 350 ℃ temperature range selection of thermocouple; If more than 350 ℃ temperature range of the object being measured in the selection of thermocouple. Of thermocouple and thermocouple installed at the same time, should pay attention to temperature measuring accurate, safe and reliable and convenient maintenance, and shall not affect the equipment operation and production operations. To meet the above requirements, in the choice of thermocouple and thermocouple installation site and insertion depth should pay attention to the following points 1, in order to make the measurement end of the thermocouple and the thermocouple, and had good heat exchange between the measured medium, should choose the observation points, try to avoid the valve, elbow and pipe and equipment near the corner of the furnish thermocouple or thermocouple, thermocouple with a protective casing and thermocouple with heat transfer and heat loss. At the same time in order to reduce the measurement error, thermocouple and thermocouple should have enough insert depth: 1, for the measurement of pipeline fluid temperature thermocouple, generally should be measuring end is inserted into the pipe ( Vertical or inclined installation) 。 As the current body of pipe diameter is 200 mm, the thermocouple or thermocouple insertion depth should choose 100 mm; 2, for high temperature and high pressure and high velocity of temperature measurement, Such as main steam temperature) , in order to reduce cases of fluid resistance and prevent cases break under the action of a fluid, can take protecting tube shallow inserted way or use hot thermocouple. Shallow inserted type thermocouple protection tube, its depth into the steam pipe should be no less than 75 mm; Heat sets the standard of thermocouple insertion depth is 100 mm; 3, if need to measure is the temperature of flue gas, although the flue is 4 m in diameter, thermocouple or thermocouple insertion depth of 1 m. 4, when measuring the original insertion depth of more than 1 m, shall be installed vertically, as far as possible or add racks and protecting tube.