Thermocouple working principle
发表日期：2016-01-09
When there is a circuit composed of two different conductor or semiconductor a and B, whose two ends are connected to each other, as long as two nodes at different temperature, end temperature T, said is a working end or the hot end, the other end temperature T0, said the free end (also known as reference end) or cold end, loop will produce an electric potential, the electromotive force of the direction and magnitude of a conductor material and two contact temperature. This phenomenon called "thermoelectric effect", consisting of two conductor loop called the thermocouple, the two conductors called "thermoelectric pole", the electromotive force generated is called "thermal electromotive force".
Thermoelectric EMFs by two part of the electric potential, the part is two conductor contact electromotive force, another part is thermo electromotive force of a single conductor.
The size of the loop thermocouple thermoelectric EMFs, and composition of the temperature of the thermocouple conductor material and two contact related, but has nothing to do with the shape and size of thermocouple. When fixing the thermocouple two electrode materials, thermoelectric power is two T and the junction temperature of t0. The difference of function.
This relationship has been widely applied in practical. Because of the constant cold end T0, thermocouple thermoelectric EMFs only with the hot end (measurement) end of the temperature change and change, namely the thermoelectric EMFs corresponds to a certain temperature. As long as we use a measurement method of thermal electromotive force can achieve the purpose of temperature measurement.
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 (Seebeck effect). Two different components of the homogeneous conductor for power, high temperature of the end to end, the lower the temperature of the end to the free end of the free end, 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. Thermocouple temperature measurement requirements of the cold end (end measurement is a hot end and connected with the measurement circuit through the lead end known as cold end temperature remains constant, the thermal electromotive force only and temperature measurement is a certain proportion of the. If the measurement is cold, the temperature change of the cold end will seriously affect the accuracy of the measurement. Take certain measures in the cold end compensation for the cold end temperature change caused by the impact of the cold end of the thermocouple called normal. Special compensating wire for connecting with measuring instrument.
Calculation method of thermocouple cold end compensation:
From millivolts to temperature: temperature at the cold junction is measured and converted to corresponding millivolt value, and the thermocouple MV values are added, the conversion temperature;
MV: to measure the actual temperature and cold end temperature from the temperature to, were converted to millivolt values, after subtracting obtained millivolt values and temperature.
Thermoelectric EMFs by two part of the electric potential, the part is two conductor contact electromotive force, another part is thermo electromotive force of a single conductor.
The size of the loop thermocouple thermoelectric EMFs, and composition of the temperature of the thermocouple conductor material and two contact related, but has nothing to do with the shape and size of thermocouple. When fixing the thermocouple two electrode materials, thermoelectric power is two T and the junction temperature of t0. The difference of function.
This relationship has been widely applied in practical. Because of the constant cold end T0, thermocouple thermoelectric EMFs only with the hot end (measurement) end of the temperature change and change, namely the thermoelectric EMFs corresponds to a certain temperature. As long as we use a measurement method of thermal electromotive force can achieve the purpose of temperature measurement.
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 (Seebeck effect). Two different components of the homogeneous conductor for power, high temperature of the end to end, the lower the temperature of the end to the free end of the free end, 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. Thermocouple temperature measurement requirements of the cold end (end measurement is a hot end and connected with the measurement circuit through the lead end known as cold end temperature remains constant, the thermal electromotive force only and temperature measurement is a certain proportion of the. If the measurement is cold, the temperature change of the cold end will seriously affect the accuracy of the measurement. Take certain measures in the cold end compensation for the cold end temperature change caused by the impact of the cold end of the thermocouple called normal. Special compensating wire for connecting with measuring instrument.
Calculation method of thermocouple cold end compensation:
From millivolts to temperature: temperature at the cold junction is measured and converted to corresponding millivolt value, and the thermocouple MV values are added, the conversion temperature;
MV: to measure the actual temperature and cold end temperature from the temperature to, were converted to millivolt values, after subtracting obtained millivolt values and temperature.
