Generic MAX6675 Thermocouple Sensor Module - K-Type, SPI Interface

The module requires a 5V DC supply for proper operation. While the MAX6675 IC itself can tolerate 3.3V logic on its SPI lines (SO, CS, SCK), the module's VCC pin must be supplied with 5V. For 3.3V microcontroller systems, ensure logic level translation is used for the SPI signals if the MCU is not 5V tolerant.

Connect the thermocouple wires to the module's '+' and '-' screw terminals. Industry standard for K-type thermocouples typically uses a yellow wire for positive (+) and a red wire for negative (-). If temperature readings decrease when the probe tip is heated, reverse the connections. The module includes high-impedance differential inputs to minimize errors from lead resistance.

The module uses a standard SPI (Serial Peripheral Interface) protocol. The microcontroller must initiate communication by pulling the CS pin low, then provide clock pulses on the SCK pin to read a 16-bit data packet from the SO pin. This packet contains the 12-bit temperature value and status bits for thermocouple break detection.

The MAX6675 IC is factory-calibrated, and the module does not require user calibration. Its specified accuracy is ±1.5°C (approximately 8 LSB) for the temperature range of 0°C to +700°C, with a resolution of 0.25°C. Accuracy outside this range or with poor wiring may vary.

The built-in detection circuitry monitors the thermocouple connection. If the thermocouple wire opens or breaks, the module sets a specific status bit in the SPI data output. This allows the host microcontroller to identify a sensor fault, enabling failsafe operation in critical monitoring applications instead of reporting erroneous temperatures.