One, what is a thermocouple
Thermocouple is the industry of the most commonly used temperature detecting element of, the work principle of the thermocouple is based on the effect of Seebeck seeback that two different components of the conductor ends connected into a circuit, such as two connecting end temperature different, in the loop produced the current thermal physical phenomena.
Two, the basic principle of thermocouple temperature measurement
Thermocouple is a temperature sensing element, is a primary instrument, the direct measurement of the temperature and the temperature signal is converted into a thermoelectric EMFs signal, again through the electric instrument (two meters) into the temperature of the measured medium.
Basic principle of thermocouple is two kinds of different components of the material composed of a conductor loop, when the temperature gradient at the two ends there, the loop will have current through. At this time between the two ends of the exists electromotive force -- thermoelectric EMFs, this is the so-called Seebeck effect.
Two different components of the homogeneous conductor for the thermal power, the temperature of the higher end of the working end, the lower end of the temperature for the free end, the free end is usually at a constant temperature. According to the functional relationship of thermo electromotive force and temperature, thermocouple indexing table was made; indexing table are obtained at 0 DEG C temperature of the free end condition, different thermocouples with different indexing table.
In the thermocouple loop access the three kinds of metal materials, as long as the material of two contacts are at the same temperature, thermocouple thermoelectric is poised to remain unchanged, that is not subject to the effects of a third metal connected to a loop in the. Therefore, the temperature at the thermocouple, can access measurement instruments, thermal electromotive force measured, you can know the temperature of the measured medium.
A thermocouple is welded to the conductor or semiconductor B and A of the two different materials to form a closed circuit, as shown in fig..
When there is a temperature difference between the conductor A and the B two rigid points 1 and 2, the electric potential is generated between the two, thus forming a current in the loop, which is called the thermoelectric effect. Thermocouple is the use of this effect to work.
Two different components of the conductor (known as thermocouple wire or thermocouple wire) are connected to the synthesis loop, when the junction temperature is not at the same time, in the loop will produce electromotive force, this phenomenon is called the thermoelectric effect, and this electromotive force is called the thermal potential. Thermocouple is the principle of temperature measurement, which is directly used to measure the temperature of one end of the medium called the working end (also known as the measurement side), the other end is called the cold end (also known as the compensation side), cold end and the display instrument or supporting instrument connection, the display instrument will point out the thermocouple thermoelectric potential.
Thermocouple is actually a kind of energy converter, which converts heat energy into electric energy, which is used to measure temperature, and it should pay attention to the following problems:
1: thermocouple thermoelectric potential is the temperature difference between the two ends of the thermocouple, rather than the temperature difference between the two ends of the temperature function;
2: thermocouple generated by the size of the thermoelectric power, when the thermocouple material is uniform, and the length and diameter of the thermocouple has nothing to do, only with the thermocouple material component and the temperature difference between the two ends of the;
3: when the thermocouple wire material composition of the two components determine the size of the thermocouple thermal potential, only with the thermocouple temperature difference; if the thermocouple cold end of the temperature to maintain a certain, the thermocouple thermocouple thermoelectric power is only a single function of the working end temperature.