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Issue 22.6 ('Preemptive Threads')
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FEATURE

Ambient and Infrared Temperature Sensor

More Raspberry Pi Fun

Issue: 22.6 (November/December 2024)
Author: Eugene Dakin
Author Bio: Eugene works as a Senior Oilfield Technical Specialist. He has university degrees in the disciplines of Engineering, Chemistry, Biology, Business, and a Ph.D. in Chemical Engineering. He is the author of dozens of books on Xojo available on the xdevlibrary.com website.
Article Description: No description available.
Article Length (in bytes): 17,410
Starting Page Number: 29
Article Number: 22605
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Excerpt of article text...

Infrared sensors allow temperatures to be measured in applications where contact thermometers cannot be implemented or are difficult to use. A few examples of applications where infrared measurement is preferable include rotating electric motors, conveyor belts, moving machinery, and areas near electrical power with high voltages.

There are many types of infrared sensors, and this article uses an MLX90614 sensor mounted on a GY-906 board. This configuration is quite common and can be purchased from many online stores. Some differences in sensors include target size and distance, surface type, temperature range, and whether they are on a portable or fixed mount (see Figure 1).

Three measurements are taken from the MLX90614 infrared sensor: ambient temperature, object temperature, and emissivity. When the button is pressed, a timer starts and is set to read the measurements every 300 milliseconds, which is about three times per second.

Ambient temperature refers to the surrounding temperature of the GY-906 board, while the object temperature is the infrared energy (as temperature) emitted from the object. For example, if you hold the sensor up to the canal in your ear, the MLX90614 would measure the infrared heat from your ear, which should be about 35.8 ?C to 38.0 ?C, or 96.4 ?F to 100.4 ?F.

Emissivity is a measurement of the surface type being measured. Emissivity is a ratio of the energy radiated. Human skin has an emissivity of 1.0, meaning that the energy emitted by skin, also known as a black body, is 100%, or 1.0. Objects and metals with low emissivity values do not typically provide accurate object temperature readings. Low emissivity values, such as those of polished or shiny surfaces, are reflective and have lower emissivity values.

Table 1: Emissivity Values (Omega, https://assets.omega.com/pdf/tables_and_graphs/emissivity-table.pdf, accessed 16 June 2024.)

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