Tag Archives: Infrared Thermopile Sensor

Infrared Thermopile Sensor for the Raspberry Pi

The usual process for measuring temperature is to place the probe directly touching the surface whose temperature is to be measured. That assumes the sensor is placed on the tip of the probe and must be in contact with the surface of interest. However, heat is a radiation and as infrared rays emanating from the surface carry information about how hot the surface really is, it should be possible to measure temperature remotely. Texas Instrument has designed a contact-less infrared thermopile sensor, the TMP006, and Adafruit is offering this on a breakout board suitable for the popular single board computer, the RBPi or Raspberry Pi.

Therefore, using this Infrared Thermopile Sensor with the RBPi, you can measure temperature of an object without touching it. The TMP006 is an embedded thermopile sensor that absorbs Infrared radiation emitted by a surface towards which you point it. It generates a small voltage proportional to the radiation falling on it, which the RBPi substitutes in a polynomial equation. The RBPi solves the equation, thereby converting the voltage into degrees, either Centigrade or Fahrenheit, as the user requires. TMP006 is capable of measuring over an area, so it is handy for determining the average temperature of an object.

As the TMP006 sensor comes in an ultra-small package, a BGA with 0.5mm pitch, it is impossible to solder manually. That is why Adafruit is offering this sensor already soldered on an easy to use breakout board. As the sensor works with three or 5V logic, no logic shifting is necessary to interface it with the RBPi. The sensor IC has two address pins and works with the I2C protocol. Therefore, you can hook up eight such TMP006 sensors to the RBPi, should you need to expand on the measurement. The Adafruit board has a 0.1” breakaway header to allow easy soldering, making it easy for using the sensor on a breadboard. The board also has two mounting holes for attaching it to an enclosure.

Users must note that TMP006 works by measuring the emissivity of an object. The sensor is suitable for measuring the temperature of a surface that has an emissivity greater than 0.7. The surfaces of most polished and shiny metal objects have an emissivity value too low for use with the TMP006. However, for measuring the temperature of surfaces with low emissivity, you can paint it with lampblack paint, which has an emissivity of 0.96.

The TMP006 accurately detects signals in almost the entire field of view of the sensor. For calculation of the final temperature, the sensor integrates all the signals present in the field of view. Therefore, more the signal that the IR sensor can capture from the target better is the accuracy of its measurement.

The percentage of signal absorbed by the IR sensor depends on the angle of incidence of the signal with respect to the sensor. Therefore, for best results, you must place the TMP006 directly underneath the target object. This will make the surface of the target parallel to the TMP006, and the angle of incidence between them will then be zero degrees, allowing the sensor to capture the maximum amount of signal.