We launched our indoor air quality monitor AirGradient ONE at the beginning of this year. We measure PM, CO2, TVOCs, temperature and humidity. When we started the development we would have never thought that achieving an accurate temperature measurement was by far the most difficult thing.
It took us 8 hardware iterations to get it right! We experienced with different enclsoure shapes, orientations and PCBs (component placement).
Our experience is similar to the author of this article:
Your biggest enemy is internal heat produced by active components, mainly the MCU but also by other sensors like the PM sensor and CO2 (NDIR).
How we solved it:
1) Minimize heat from energy by using components that have low energy consumption and make extensive use of sleep functions of the MCU as well as sensor components (e.g. PM sensors can be put to sleep).
2) Make use of physics. Our monitor is wall mounted and uses the convection mechanism. So nearly all components that heat up like LEDs, MCU etc. are located at the very top inside the enclosure. Optimize the vents at the top and bottom of the enclosure and create an unobstructed air flow through the enclosure based on natural convection.
3) Plan for enough space. To get temperature right, you need a lot of air around the temperature sensor that is free from radiation from other heat sources. So we specifically designed the PCB to have the temperature sensor at a 'finger' at the bottom with a lot of space to other components and ensured there is a good air flow around.
If you are interested to see our design, have a look at our open-source, open-hardware DIY Pro monitor [1].
We integrated a lot of the things we learned designing the commercial monitor mentioned above into these build instructions [2] that allow you to build your own highly accurate monitor and then also be able to change the firmware and adjust to your needs. In fact, our kit contains exactly the same plastic injected enclosure we use for our commercial monitor (but you can also just 3D print the one from the build instructions and get the other parts by yourself).
[1] https://www.airgradient.com/open-airgradient/kits/ [2] https://www.airgradient.com/open-airgradient/instructions/di...