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Air Quality Shorts: Part 1 - Temp and Humidity Sensors

Good Air Quality Sensing Starts With Temperature & Humidity.

Whether you are measuring CO2, Particulate or VOC, it is vitally important to have a benchmark of Temperature and Relative Humidity (written as “RH%”). This is because most of the readings you are observing are related to particles carried in air. The air that carries the chemicals and compounds is affected by Temp and RH% as its density for once will change, and a range of other factors. Secondly, if the air is warmer it will have more kinetic energy, and so if you are wanting to relate one reading on a cool dry day to a warm humid day, or a cold damp day to a hot dry day - you will need these two data points to stand a chance of correlating these multivariate factors.

Jude holding Temp & RH Sensor

Even if you are not sure how to do this, the point is to get the Temp and RH% logged, so you have the data to retrospectively improve.

Close up of sensor on PCB


Some sensors do actually have Temp and RH% sensors onboard so this may not always be needed, but as these SHT4x sensors are so cheap, it’s likely you’ll add one anyway for robust readings.

Jude holding sensor PCB

The Video gives an overview of the SHT40 sensor used in the DesignSpark ESDK, but of course, you can also buy these attached to breakout boards also if you are not planning to build a PCB from scratch.

Sensor guide showing breakout boards

Showing the SHT40 sensor, with the recommended ‘cut-out’ around it to allow thermal isolation. This and many other useful tips are detailed in the Sensirion Design Guides, available from their website.

Sensor guide showing recommended cut-out

They also cover some useful background info on what Humidity and Relative Humidity actually mean.

Sensor guide showing definitions

If you are interested, check out the website for details:

The Air Quality Shorts Series.

The following series will give you an overview of sensors of interest. Right now we have:

But stay tuned, as we also have more sensors in development! So follow this Article for updates...

Winner of the 2020 Alastair Graham-Bryce "Imagineering" Award (IMechE), Jude thrives in high risk collaborations, uncertainty and pressure - drawing from global networks and experiences to deliver high profile campaigns and digital/physical products. A leading Creative Technologist & Physical Prototyping Expert, Jude has worked for NHS, Dyson, LEGO, and a number of start-ups. He is one of the eight featured inventors in BBC Two's Big Life Fix.
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