Basic principle of single-head tube temperature measurement

According to the functional relationship between thermal electromotive force and temperature, the single-head tube index table is made; the index table is obtained under the condition that the temperature of the free end is 0°C, and different single-head tubes have different index tables.

 

The single head tube is the temperature sensing element and the main instrument. It directly detects the temperature and converts the temperature signal into a thermal electromotive force signal, and then converts it into the temperature of the measured medium through an electrical instrument (secondary instrument).

 

The basic principle of single-head tube temperature measurement is that two material conductors with different compositions form a closed loop. Overvoltage occurs in a circuit when there is a temperature gradient in the circuit. At this time, an electromotive force is generated between the two ends-the thermal electromotive force, which is the so-called Seebeck effect.

 

When the third metal material is connected to the single-head tube circuit, as long as the two junction temperatures of the material are the same, the thermoelectric potential generated by the single-head tube will remain unchanged, that is, it will not be affected by the third metal connected to the circuit . influences. Therefore, when measuring the temperature of the single-head tube, the measuring instrument can be connected, and the temperature of the measured medium can be known after the thermal electromotive force is measured. Two uniform conductors of different composition are thermodes, the hotter end being the office end and the cooler end being the free end, usually at a constant temperature.

 

When there is a temperature difference between the two connection points 1 and 2 of the conductors A and B, an electromotive force will be generated between the two, thus forming a large and small current in the circuit. This phenomenon is called the thermoelectric effect. Single head tubes use this effect to work.

 

Two conductors from different elements (called single-ended wires or thermodes) are connected at both ends to form a loop. When the junction temperature is different, an electromotive force is generated in the circuit. This phenomenon is called thermoelectric effect, and this electromotive force is called thermoelectromotive force. The single-head tube uses this principle to measure temperature. Among them, one end directly used to measure the temperature of the medium is called the working end (also called the measuring end), and the other end is called the cold end (also called the compensation end); the thermoelectric potential generated by the tube.