Specific use of thermocouples in production in various industries

Thermocouples are used to measure furnace temperature. The thermocouples with response divisions are mainly selected according to the high or low target temperature. Of course, it is also necessary to consider whether the measured atmosphere is reducing or oxidizing. However, if armored thermocouples are used, I have not considered too much the impact of redox atmosphere on the life and measurement accuracy of thermocouples.

The requirements are slightly stricter. Most furnaces need to be connected with two upper thermocouples. Among them, at least one should be used for temperature control and the other for recording. Because our processing process must be traceable. Specific use of thermocouples in production in various industries

When encountering a relatively large furnace body (more than 5 meters in length), it should be divided into several temperature zones for independent measurement and control. For example, the upper, middle and lower partitioning method, etc. More stringent furnaces should be tested for furnace temperature uniformity regularly. That is, multiple thermocouples (or other sensors) are evenly arranged in the working area to simulate normal use and load to test whether the temperature of the furnace body is uniform over time and other factors. That is, whether the temperature measurement point of the temperature control thermocouple can represent the actual temperature of the furnace temperature. Multiple measurements take their own values.

Thermocouples are mainly used for measurement and calibration.
Moreover, thermocouples are primary instruments that convert temperature into electric potential. This weak electric potential must be transmitted to secondary instruments for processing, display or printing.
Secondary instruments are divided into analog and digital types. Now they are basically digital.

A thermocouple cold end temperature compensation circuit, which includes a voltage temperature sensor TMP35 and a K-type thermocouple. The working principle of the thermocouple is to generate an electric potential difference based on the temperature difference between the hot end and the cold end. Since the temperature of the cold end is often not 0℃ during actual measurement, the thermocouple must be temperature compensated. The thermocouple temperature compensation formula is as follows:

E (t, 0) = E (t, t0) + E (t0, 0)

Among them, E (t0, 0) is the actual measured electromotive force, t represents the hot end temperature, t0 represents the cold end temperature, and 0 represents 0℃. In the field temperature measurement, since the cold end temperature of the thermocouple is generally not 0℃, but changes within a certain range, the measured thermoelectric potential is E (t, t0). If you want to measure the thermoelectric potential E (t, 0) corresponding to the actual measured temperature, you must compensate for the compensation potential E (t0, 0) required for the cold end not to be 0℃. Moreover, the characteristics of the compensation potential changing with the cold end temperature must be consistent with the thermoelectric characteristics of the thermocouple, so as to obtain a better compensation effect. This is a circuit diagram for thermocouple cold end temperature compensation. The temperature sensor TMP35 completes the temperature compensation work very well. The voltage output by TMP35 is first divided by a resistor and then amplified by an amplifier, which is the E (t0, O) corresponding to the K-type thermocouple.