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%. The thermocouple inputs are protected against overvoltage conditions up to ±45V.
A lookup table stores linearity correction data for several types of thermocouples (K, J, N, R, S, T, E, and B). Line frequency filtering of 50Hz and 60Hz is included, as is thermocouple fault detection. A SPI-compatible interface allows selection of thermocouple type and setup of the conversion and fault detection processes.
- Provides High-Accuracy Thermocouple Temperature Readings
- Includes Automatic Linearization Correction for 8 Thermocouple Types
- ±0.15% (max, -20°C to +85°C) Thermocouple Full-Scale and Linearity Error
- 19-Bit, 0.0078125°C Thermocouple Temperature Resolution
- Internal Cold-Junction Compensation Minimizes System Components
- ±0.7°C (max, -20°C to +85°C) Cold-Junction Accuracy
- ±45V Input Protection Provides Robust System Performance
- Simplifies System Fault Management and Troubleshooting
- Detects Open Thermocouples
- Over- and Undertemperature Fault Detection
- 50Hz/60Hz Noise Rejection Filtering Improves System Performance
- 14-Pin TSSOP Package
CNC.xyz MAX31856 Breakout Board
9-Pin 0.100" Header
|1||VIN||Input 3.3-5 VDC to board|
|2||3V3||Output 3.3 VDC from the regulator|
|5||SDO||Serial Data Out|
|6||SDI||Serial Data In|
|7||CS||Serial Chip Select|
|8||DRDY||Data Ready - Active Low|
|9||FAULT||Fault - Active Low|
2-Pin 0.100" Terminal Block
|1||TC+||Thermocouple Input (positive)|
|2||TC-||Thermocouple Input (negative)|
- VIN - Power input can range from 3.3-5VDC.
- 3V3 - Power output from the 3.3V on-board regulator.
- GND - Power / logic ground.
- SCK - This is the serial clock.
- SDO - Serial Data Out or Master In Slave Out (MISO) for data sent from the MAX31856 chip.
- SDI - Serial Data In / Master Out Slave In (MOSI) for data sent to the MAX31856 chip.
- CS - Chip Select for data transmission, active low.
There are also two pins available for signaling in varying installations where additional functionality is desired for example in 3D printers and CNC machines.
- DRDY - Data Ready for situations where the MAX31856 chip processes averages that may take several processing cycles to calculate, active low.
- FAULT - Fault signal which can be configured to trigger under varying conditions (open thermocouple, shorted thermocouple, outside of normal range... etc.), active low.
You can download our Arduino Library from our Github page: https://github.com/CNCxyz/MAX31856
Bill of Materials (BOM)
|Line #||Quantity||Part Code||Description|
|1||1||IC1||MAX31856 Thermocouple Chip|
|2||1||U1||SPX3819 3.3V Voltage Regulator|
|3||3||R1, R2, R3||100 ohm Resistor 0603|
|4||1||R4||330 ohm Resistor 0603|
|5||2||C1, C2||1.0uF Capacitor 0603|
|6||5||C3, C4, C5, C6, C7||0.1uF Capacitor 0603|
|7||1||FAULT||Red LED 0603|
|8||1||J1||2 Position Terminal Block|
|9||1||J2||9 Position Header|