02-16-2024 07:12 PM
I have been experimenting with the BME680's gas sensing using 5 BME680 breakout boards inside a small gas chamber. I am using an ESP32, BSEC2 library, and sampling every 3 seconds on LP mode. Here is one test I ran a few times:
- Ran the BME680's for multiple days until IAQ accuracy reached 3
- Flush chamber with ultra zero air until readings stabilize (https://www.calgasdirect.com/gasco-105l-1-zero-air-calibration-gas-20-9-o2-balance-nitrogen-a-105-li...)
- Fill chamber with 1ppm isobutylene in Nitrogen calibrated gas until readings stabilize (https://www.calgasdirect.com/isobutylene-calibration-gas-c4h8-1-ppm-balance-nitrogen-in-a-103-liter-...)
The BME680's bVOC values immediately get pinned at 1000ppm when the gas enters the chamber. I understand it is calibrated to a different gas mixture, but there isn't anything that can explain a 1000x difference. Isobutylene has a molecular weight of 56.1 g/mol and I calculated the bVOC gas mixture to have a molecular weight of 51.29 g/mol. I would appreciate any help or thoughts people have.
Thanks!
Solved! Go to Solution.
03-19-2024 02:11 AM
Hi mhoff87,
Did you have further feedback?
03-21-2024 04:53 PM
Hi BSTRobin,
I will run this test when I get the chance and get back to you.
Thank you,
Mark
03-25-2024 06:33 PM - edited 03-25-2024 08:03 PM
I ran air>Isobutylene>air. Attached are graphs of the results. Tests were run at 4800ft (1463m) above sea level.
04-25-2024 11:04 AM
Hi mhoff87,
Thank fo your feedback.
We think you didn't get the point,
when testing 'Isobutene', you should mix filed air with isobutene, not all isobutene.
As we mentioned before, our sensor can not operate without oxygen.
05-29-2024 10:32 AM
Hi mhoff87,
Did you have further feedback?