Cold-Junction Compensated, 1-Wire Thermocouple-to-

By Maxim Integrated 129

Cold-Junction Compensated, 1-Wire Thermocouple-to-

Maxim's MAX31850/MAX31851 cold-junction compensated, 1-Wire® thermocouple-to-digital converters perform cold-junction compensation and digitize the signal from a K-, J-, N-, T-, S-, R-, or E-type thermocouple. The converters resolve temperatures to 0.25°C, allow readings as high as +1768°C and as low as -270°C, and exhibit thermocouple accuracy of 8 LSBs (2°C) for temperatures ranging from -200°C to +700°C.

Communication with the master microcontroller is over a 1-Wire bus that by definition requires only one data line (and ground) for communication. Operating power can be obtained directly from the data line ("parasite power"), eliminating the need for an external power supply.

Each device has a unique 64-bit serial code, which allows multiple units to function on the same 1-Wire bus. Therefore, it is simple to use one microcontroller (the master device) to monitor temperature from many thermocouples distributed over a large area.

Four location address inputs simplify mapping of individual units to specific locations.

  • Cold-junction compensation
  • Versions available for multiple thermocouples types: MAX31850 supports K-, J-, N-, T-, and E-types; MAX31851 supports S- and R-types (see table 1 in the full data sheet)
  • Detects thermocouple shorts to GND or VDD
  • 14-bit, 0.25°C resolution
  • 1-wire interface (read-only); power can be obtained from interface (parasite-powered mode)
  • Detects open thermocouple