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!
