Access in the thermocouple loop when the third metal material, the two contacts at the same temperature as long as the material, produced by the thermocouple thermoelectric is set to remain the same, which is not affected by the third metal access in the loop.
Therefore, when the thermocouple temperature measurement, can be connected to the measuring instrument, measured after the thermoelectric emfs, can know the temperature of the measured medium.
Thermocouple measuring temperature to the cold end (
Measure the end for the hot end, by the end of the lead connected to the measurement circuit is called cold junction)
Temperature remains constant, the size of thermoelectric potential and measured temperature in certain proportion relationship.
When measuring, the cold end (
Changes in temperature, will be affected the accuracy of measurement.
Take action at the cold end compensation due to the impact of the cold end temperature change is called the thermocouple cold junction compensation.
Attachment: thermocouple cold junction compensation calculation method: from millivolt to temperature: measure the cold end temperature and conversion for the corresponding millivolt values, millivolt values with thermocouple, the temperature conversion.
From temperature to millivolt: measure the actual temperature and the cold end temperature, the conversion of millivolt values respectively, would draw millivolt values working principle of two kinds of different ingredients of conductor (
Called the thermocouple wire or hot electrode)
Two ends synthesis loop, when the junction temperature is not at the same time, in the circuit will generate electromotive force, this kind of phenomenon called the thermoelectric effect, and the electromotive force called thermoelectric potential.
Thermocouple is to use the principle of temperature measurement, which directly used for measuring the medium temperature is called at the end of the working side (
Also known as the measuring end)
, on the other side called cold end (
Also known as compensation)
The cold end connected to the digital display table or meter, display instrument will point out the thermocouple thermoelectric potential.
Thermocouple is actually a kind of energy converter, it converts heat into electricity, using thermoelectric potential generated by the measuring temperature, for the thermocouple thermoelectric potential, we should pay attention to the following questions: 1, the thermocouple thermoelectric potential is thermocouple temperature on both ends of the work of the [
Degree function is poor, rather than the thermocouple cold end with the job, a function of temperature difference on both ends.
2, the size of the thermocouple thermoelectric potential produced by, when material is uniform thermocouple, has nothing to do with the length and diameter of thermocouple, only with the thermocouple at the ends of the material composition and temperature difference.
3, when the two thermocouple wire thermocouple material composition is determined, the size of the thermocouple thermoelectric potential associated with the temperature difference of thermocouple, only if the thermocouple cold end temperature keeping, this into the thermocouple thermoelectric potential is only the end temperature of single value function.
Will be two different welding material A conductor or semi-conductor A and B, form A closed loop, when the conductor A and B two persistent point temperature difference between 1 and 2, occurs between the electromotive force, thus forming the size of A current in the circuit, this kind of phenomenon called the thermoelectric effect.
Thermocouple is in using this effect to work.