Thermocouple Thermometer - Thermoelectric Effect Temperature Measurement
Definition:
A pair of conductors of different materials that produce an electric potential in a circuit based on the Zerbeck effect. A sensitive element in which a pair of conductors of different materials are joined together at one end and the thermoelectric effect is applied to achieve temperature measurement.
Overview :
A thermocouple is a temperature sensing element that is an instrument. It measures the temperature directly and converts the temperature signal into a thermoelectric potential signal, which is converted into the temperature of the medium being measured by an electrical instrument (secondary instrument). The basic principle of thermocouple temperature measurement is two different components of the material conductors form a closed loop, when the two ends of the temperature gradient exists, there will be a current through the loop, at this time there is an electric potential between the two ends of the electric potential - thermoelectric potential, which is known as the Seebeck effect. Two homogeneous conductors of different compositions are hot electrodes, the higher temperature end is the working end and the lower temperature end is the free end, which is usually at some constant temperature. According to the thermal electromotive force as a function of temperature, the thermocouple scale; scale is the free end of the temperature in the conditions of 0 ℃, different thermocouples have different scales.
In the thermocouple circuit access to a third metal material, as long as the temperature of the two contacts of the material is the same, the thermal potential generated by the thermocouple will remain unchanged, i.e., unaffected by the access of the third metal in the circuit. Therefore, in the thermocouple temperature measurement, can be connected to the measuring instrument, measured after the thermal potential, you can know the temperature of the measured medium.
Thermocouple temperature measurement requires its cold end (measuring end for the hot end, through the lead and the measuring circuit connected to the end is called the cold end) of the temperature remains unchanged, the size of the thermoelectric potential and the measurement of the temperature is a certain proportionality. If the temperature of the cold end (environment) changes during measurement, the accuracy of the measurement will be seriously affected. In the cold end to take certain measures to compensate for the cold end of the temperature change caused by the impact of the cold end of the thermocouple is called the cold end of the compensation.
Attachment: thermocouple cold end compensation calculation method: from millivolt to temperature: measure the temperature of the cold end, converted to the corresponding millivolt value, and the thermocouple's millivolt value is added, converted to temperature. From temperature to millivolt: Measure the actual temperature and the cold end temperature, convert them to millivolt value, subtract them to get the millivolt value, that is to say, the temperature.
