The MAX6675 is a complicated monolithic thermocouple digitizer, built-in signal booster, 12-bit analog / digitalized thermocouple converter, cold-junction compensation sensor and corrector, digital controller, one SPI interface and one relevant logic controller.
The MAX6675 is with signal conditioning amplifier inside converting thermocouple signal to voltage signal compatible with ADC input signal. Connect T and T-input terminal to low noise amplifier A1 to detect high precision of input signal and insulate thermocouple wire and interference source. Thermoelectric force output from thermocouple will be amplified by A1, buffered in A2 voltage follower and transmitted to ADC. Before converting temperature voltage value to equivalent temperature value, users need to compensate temperature of the thermocouple cold junction. Cold junction temperature is the difference value between ambient temperature and 0' actual reference value.
The thermocouple functions as detecting temperature difference between hot and cold junction. Thermocouple hot nodes temperature ranges from 0'C to 1023.75'C. Cold junction temperature is the ambient temperature of circuit board installing CJMCU-MAX6675, which ranges from 20'C~85'C. When cold junction temperature fluctuates, the MAX6675 can detect the temperature change of hot end precisely.