Overview of temperature daughter boards
The Duet range of machine controllers support one or more temperature daughter boards which provide expanded temperature sensor connectivity using Maximum integrated ICs. These daughter boards connect to the Duet digitally over SPI.
Number of temperature daughter boards supported
The Duet 3 6HC and 3HC each support up to two temperature daughter boards stacked. PT100 and Thermocouple daughter boards can be mixed and matched. The Duet 3 Toolboard 1LC does not support a temperature daughter board.
The Duet 2 WiFi and Duet 2 Ethernet support up to two temperature daughter boards stacked, with a further two stacked on the Duex2 or 5. This provides a total of 8 digital temperature inputs. PT100 and Thermocouple daughter boards can be mixed and matched.
The Duet 2 Maestro supports 1 temperature daughter board for two SPI temperature input channels. On the Maestro either a Thermocouple or PT100 daughter board can be connected, but not both.
There have been two versions of the thermocouple board. the change from version 1.0 to 1.1 was to made to move to the MAX31856 sensor IC.
Version 1.1 thermocouple boards
- MAX31856-based daughter boards each supporting two thermocouples of type B, E,J K, N, R, S or T.
- MAX31855-based daughter boards, each supporting two K-type thermocouples
For setting up Duet controllers to use thermocouple sensors see: Connecting thermocouples
MAX31856 sensor IC details
The MAX31856 performs cold-junction compensation and digitizes the signal from any type of thermocouple. The output data is formatted in degrees Celsius. This converter resolves temperatures to 0.0078125°C, allows readings as high as +1800°C and as low as -210°C (depending on thermocouple type), and exhibits thermocouple voltage measurement accuracy of ±0.15%. See the Maxim integrated website for more details on the MAX31856.
Other Temperature sensors
The Duet range of machine controllers support various other temperature sensors. See: