Medium low temperature measurement system based on K-type thermocouple

Temperature is a very basic physical quantity, and many physical quantities are closely related to it. Therefore, the correct measurement and precise control of temperature are of great significance in agriculture and industrial production, people's daily life, and scientific research. At present, thermocouple sensors are the most common temperature measuring components in the domestic and foreign instrumentation industry, and are also the most widely used thermoelectric sensors in the field of contact temperature measurement.
K-type thermocouple, as a major temperature measuring element, has the characteristics of simple structure, convenient use, wide temperature measurement range, and high temperature measurement accuracy. However, there are several issues with the application of K-type thermocouples.
1) Nonlinear. The output thermoelectric potential of thermocouples is non-linear with temperature, therefore linearization is necessary for application.
2) Cold compensation. The thermoelectric potential output by the thermocouple is the difference between the potential at the cold end when it is maintained at 0 ℃ and the measuring end. However, in practical applications, the temperature at the cold end varies with the ambient temperature, so cold end compensation is required.
3) Signal output. The output signal of K-type thermocouple is an analog signal. In order to facilitate connection with subsequent microcontroller circuits, it is necessary to convert the analog signal into a digital signal.
MAX6675 [0] is a thermocouple amplifier and digital converter that integrates thermocouple amplifier, cold junction compensation, A/D converter, and SPI serial port.