First thinking are the elements of the thermocouple device should measure precision, safe reliable and maintenance bento, operation and does not affect the equipment operation and consumption. To meet the above request, in the choice of thermocouple device site and insertion depth to pay more attention to the following: 1) In order to make the measurement and measurement of thermocouple side has an abundance of heat exchange between the measured medium, should be the reasonable choice of observation, as far as possible to prevent the valve, elbow and corner around pipeline and equipment installed thermocouple. 2) With a thermocouple with heat transfer and heat loss protection casing, in order to can reduce the measurement error, thermocouple and thermocouple should have enough insertion depth. (1) measurement of pipeline fluid temperature thermocouple, general conditions should be put in which measurement device or tilting device is inserted into the pipeline where vertical. For example, or flow pipe diameter is 200 mm, the thermocouple insertion depth should be 100 mm. (2) to participate in the demand of measurement is the extension of the flue temperature, so although flue is 4 meters in diameter, the thermocouple insertion depth of 1 meter can. (3) when the measuring element insertion depth beyond one meter, the vertical device, it should be possible or disguise and protect casing.