The use of the temperature instrument1

Temperature meter is the measuring instrument are used in industry, and in many areas has a very important role, users in the use of the temperature instrument for its use has knowledge, for the user's operation and maintenance are of great help, the following is to introduce the use of the temperature instrument.

1, the principle and structure of thermocouple thermometer

thermocouple thermometer is the contact of two different metal conductor, heated to produce thermoelectric potential made of the principle of measuring temperature instrument. Mainly by the thermocouple, compensation conductor and electrical measuring instrument ( Galvanometer) Of three parts. With two different conductors or semiconductor ( Hot electrode) One end of the welded to each other, to form a thermocouple work side ( Hot side) Measured medium, insert with it to measure the temperature. The free end of the thermocouple, The cold end) Respectively through wires connected to measuring instrument. When the work end and free end of the thermocouple temperature difference exists, the thermoelectric potential are produced, so there is current on the compensating conductor through, and the bigger the temperature difference, the thermoelectric potential and wires on the current. By observing the pointer deflection Angle measuring instrument, can be directly read out the temperature of the measured medium. Commonly used ordinary pin rhodium - Rhodium thermocouple ( WRLL type) The maximum temperature of 1600 ℃. The common pin rhodium - Platinum thermocouple ( WRLB) The maximum temperature of 1400 ℃. Ordinary nickel-chromium - Nickel silicon thermocouple ( WREU） The maximum temperature of 1100 ℃.

thermocouple thermometer, the advantages of high sensitivity, wide measurement range, without external power supply, is advantageous for the long distance measure and record, etc. Defect is need compensation conductor, the installation cost is more expensive. On the industrial boiler, commonly used to measure the steam temperature, furnace flame temperature and flue gas temperature.

2, install and use requirements for thermocouple thermometer

( 1) Thermocouple installation site should be easy to work, is not affected by collision, vibration, etc.

（ 2) Thermocouple must be placed in the middle of the measured medium, and should make it as far as possible to the flow direction of the measured medium into a 45 ° Angle, depth of not less than 150 mm. Measuring the temperature, the general should be vertical insertion. If vertical insert with difficulty, also can be installed horizontally, but should not be greater than 500 mm, the length of the inserted the chamber of a stove or furnace otherwise must be supported.

（ 3) Thermocouple installed, the insert application marl plug the hole, so as to avoid external after cold air invading affect measurement accuracy. Thermocouple should be protected with ceramic slowly inserted into the measured medium, so as to avoid because of protecting tube cracking temperature mutations.

（ 4) Thermocouple temperature changes in the free end had a great influence on the measured results, must often correction or free end temperature constant.

3, thermal resistance thermometer

thermal resistance thermometer is the use of a conductor or semi-conductor resistance varies with temperature change and change the nature of the made, by measuring the size of metal resistance, it is concluded that the measured temperature value. Common materials for thermal resistance are pin and copper.

thermal resistance generally want to protect casing, outside to protect casing material heat resistance, corrosion resistance, temperature under upheaval, good sealing and adequate mechanical strength.

with the temperature of the thermal resistance measurement under 500 ℃, has higher measuring accuracy than thermocouple. Pin thermal resistance can be measured 200 ℃ ~ 650 ℃, copper heat resistance can be measured 50 ℃ ~ 150 ℃ temperature range. Thermal resistance can also remote measuring and display. Installation is similar with thermocouple. Thermal resistance and temperature display instrument become temperature display device by wire connection, used to measure the temperature of the gas, liquid and steam.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor