Overview
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The MLX90614 family of sensors use infrared thermopile detectors to determine the temperature of objects without touching them. This sensor can tolerate ambient temperatures from -40 to 85°C and works for object temperatures from -70 to 382.2°C. It provides a measurement resolution of 0.02°C and has an accuracy of ±0.5°C at room temperature. The device comes in a compact TO-39 package that weighs just 0.03 oz (0.9g), and it features filters that give it immunity from ambient IR and sunlight. Please see the MLX90614 datasheet (749k pdf) for more information.
Application Examples
- Fire detector on a firefighting robot
- Movement detector
- Thermal relay with a programmable threshold (e.g. for use in a thermostat)
- Body temperature measurement
- Monitoring of component temperatures, such as motor drivers
- Multi-zone temperature control—up to 100 sensors can be read via two common wires
MLX90614 connection to SMBus. |
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Using the Sensor
The sensor supports two possible interfaces: SMBus (default) and 10-bit PWM output. The SMBus is completely compatible with I²C (also called TWI) buses for frequencies below 100 kHz and can be used to configure and enable the PWM output if so desired. In addition to the sensor’s datasheet, Melexis’s application note on MLX90614 SMBus communication (589k pdf) and our application note on interfacing Orangutans with the MLX90614 help demonstrate how to use this sensor.
Please note that accurate readings can only be achieved if the sensor is in thermal equilibrium and under isothermal conditions (i.e. there are no temperature differences across the sensor package). The measured object temperature is the average of all objects in the sensor’s field of view.
