MAX31855

Connects over

SPI

Made by

Maxim Integrated

Datasheet

datasheets.maximintegrated.com

Use it

hardware {
    device max31855: MAX31855(cs: 16)
}

every 1s {
    let value: float = max31855.temperature()
    log("max31855", "temperature={value}")
}

The MAX31855 goes on the SPI bus; give it its cs pin as an argument.

Methods

• max31855.temperature() -> float

  Thermocouple temperature °C

• max31855.internal() -> float

  Cold junction temperature °C

• max31855.is_fault() -> int

  1 if fault detected

Wiring

Specifications

Voltage

3.0V – 3.6V (NOT 5V tolerant on SPI lines)

Current

0.9 mA active

Thermocouple

K, J, N, T, S, R, E types (chip variants)

Range

−270°C to +1372°C (K-type)

Resolution

0.25°C

Tips

• Cold-junction compensation is automatic — the IC has its own temp sensor for it.
• Use the included terminal block if possible — solid solder joints to thermocouple wires can introduce a stray junction.
• Open-circuit / short-to-GND / short-to-VCC faults are reported in the status register.

Alternatives worth knowing:

• MAX31856: Programmable thermocouple type, integrated FIR filter, more features.