Thermocouples used for temperature measurement. Mainly according to the measured target temperature response index to select the thermocouple. , of course, also want to consider reducing or oxidizing atmosphere is to be tested only with thermocouple, I don't have much to consider REDOX atmosphere of thermocouple life and the influence of the accuracy of measurement. Some is a little more strict requirements, most of the furnace body to connect two a thermocouple. Which is at least one temperature control with, another recording. Because our process need to be able to trace, encounter more large furnace ( The length of 5 meters above! ) Independent survey control going into several zones. Such as 3 partitioning method and so on. More stringent furnace to furnace temperature uniformity tests on a regular basis. Is more than the thermocouple ( Or other sensors) Evenly arranged in the workspace, to simulate normal use process and load, to test with the changes of factors such as time, the furnace temperature is uniform. The temperature control of thermocouple temperature measurement points can represent the real temperature of the furnace temperature, usually only measuring the value of each take. Thermocouple applications mainly include the measurement and calibration, and thermocouple is to belong to an instrument, is converting temperature potential, the weak electric potential to deliver to secondary instrument for processing display or printing. Secondary instrument is divided into analog and digital. Basic are digital now. A thermocouple cold junction compensation circuit, circuit includes TMP35 voltage type temperature sensor and type K thermocouple. The working principle of thermocouple is according to the hot side and cold side temperature difference and produce electric potential difference. Due to the actual measurement, the cold end temperature is often not O ℃, so the thermocouple temperature compensation. Thermocouple temperature compensation formula is as follows: E ( t, 0) = E ( t, t0) + E ( t0,0） Among them, the E ( t0,0） Is the actual measuring electromotive force, t on behalf of the hot end temperature, t0 on behalf of the cold end temperature, 0 ℃ O. Temperature measurements at the scene, the thermocouple cold junction temperature is generally not as O ℃, but changing within a certain scope, therefore measured thermoelectric potential for E ( t, t0) 。 If you want to measure the real measured temperature of the thermoelectric potential (E t, 0) , it is necessary to compensate the cold end is not required to 0 ℃ compensation electric potential (E t0,0） , and the compensation characteristics of the electric potential changes with the cold end temperature must be consistent with the thermocouple thermoelectric properties, so as to obtain a good compensation effect. Is a thermocouple cold junction compensation circuit diagram. Temperature sensor TMP35 very good completed the temperature compensation, TMP35 output voltage of the resistor voltage divider first, then through the amplifier amplification, is the corresponding E K type thermocouple.