MAX31855KASA+

The MAX31855KASA+ from Analog Devices is a sophisticated cold-junction compensated thermocouple-to-digital converter designed specifically for Type K thermocouples. It integrates a low-noise amplifier, ADC, cold-junction temperature sensor, and SPI interface into a single 8-pin SOIC package. The device provides 14-bit (0.25C) resolution for thermocouple measurement and 12-bit (0.0625C) resolution for cold-junction compensation, delivering a fully digitized temperature output with no external signal conditioning required. Built-in fault detection identifies open thermocouple, short to GND, and short to VCC conditions.

The MAX31855KASA+ operates by simultaneously measuring the thermocouple voltage and the cold-junction (reference junction) temperature. A precision low-noise amplifier amplifies the small thermocouple Seebeck voltage, which is then digitized by a 14-bit sigma-delta ADC. The integrated cold-junction temperature sensor measures the reference junction at the connector point with 12-bit resolution. The device automatically performs cold-junction compensation in the digital domain, calculating the true thermocouple hot-junction temperature using the measured thermocouple voltage and cold-junction temperature. Temperature data is output through a read-only SPI interface as a 32-bit word containing thermocouple temperature, reference junction temperature, and fault status bits.

• Industrial oven and furnace temperature monitoring
• 3D printer hot-end and heated bed temperature control
• HVAC and building automation temperature sensing
• Appliance temperature measurement and safety cutoff
• Laboratory and scientific temperature measurement