e-tinkers / max31855

MAX31855 Arduino Library

MAX31855 Arduino Library

A simple and lightweigth Arduino library for MAX31855 thermocouple-to-digital convert chip. I created this library because some of similar libraries are unnecessary complicate with extra dependency library or some with wrong negative temperature reading.

Basic Usage

The basic usage of the library can be as simple as this:

#include <MAX31855.h>

#define CS 10

MAX31855 sensor(CS);

void setup()
{
  Serial.begin(115200);
  while(!Serial);
  sensor.begin();
}

void loop()
{
  Serial.print("Temperatures in Celsius- ");
  Serial.print(sensor.thermocoupleTemperature());
  delay(1000);
}

See demo.ino for more complete usage with fault detection as well as reading the internal chip(junction) temperature.

Notes

According to MAX31855 datasheet, It is strongly recommended to add a 10nF differential capacitor, placed across the T+ and T-pins, in order to filter noise on the thermocouple lines.

In additional to thermocouple temperature reading, MAX31855 also provides an output for its internal(junction) temperature reading, which can be access via MAX31855::internalTemperature(), the internal chip junction temperature provides the reading between 127 and -55 degree Celsius with precision of 0.0625/C. See datasheet for more details. Depend on where the sensor board is mounted, this internal temperature can be viewed as the temperature that is close to Ambience temperature.

The MAX31855::begin() returns a non-zero fault status, the value could be used to further detect the root cause of the the thermocouple connection fault.

Value   Root Cause
1       The thermocouple is not connected
2       The thermocouple is short with the GROUND
4       The thermocouple is short with VCC

License

MIT License. See LICENSE file for details.

max31855's Issues

Reading fail status, possible mistake

Hello, I think there is a mistake in reading the fail status. According to the datasheet, I believe that line 58 should be either:
_fault = data[3] & 0x01;
or
_fault = data[0] & 0x07;

Best regards and HNY!