imsolidstate

Air quality sensor (TVOC and eqCO2)

I’ve been curious about the inexpensive gas sensors available now and whether they are useful at all. They are being built into new equipment to estimate air quality. I decided to pick one up and attach it to my K64 dev board for some hands on evaluation.

Its very responsive, but I haven’t achieved what I want to call a steady baseline. There’s an odd requirement in the datasheet to perform a measurement every second, and you can preload a baseline reference but it’s not clear exactly what you gain from that. There is also compensation for humidity but I don’t currently have that sensor. Here in Colorado its always pretty dry anyway.
At home it is usually in the 100-200ppb range for TVOC, sometimes climbing to almost 1000. I live in an older home so I guess that isn’t a surprise, however when I reset it and it turns back on sometimes the readings will be lower. At work its rarely above about 30ppb.
Sensirion has provided a nice document that describes TVOC in more detail and gives ranges for acceptable levels. It also hints that you can calibrate the sensor with ethanol but doesn’t explain how.
If anyone has used one of these and has more information on improving accuracy please leave a comment.

Tags: Electronics