How good are measurements?
- View live demo of AQMesh vs reference installed in Stratford-upon-Avon, UK
- AQMesh performance proven by independent EuNetAir study of air quality sensor systems
- Professor Rod Jones of the University of Cambridge presents a paper showing very encouraging results for AQMesh
AQMesh has been in development, global trials and available for sale since 2013. During that time, AQMesh v.3.0 showed that trends could be identified and the product was suitable for a number of air quality applications. Developments at the end of 2014 – improvements in electrochemical sensors and the AQMesh processing algorithms – have given a dramatic improvement in performance with AQMesh v.4.0, v.4.1. and v.4.2. The process and benefits of sensor characterisation at manufacture include optimal correction for environmental factors, correction of gas span and baseline offset.
The most popular method for measuring AQMesh performance is by co-locating AQMesh pods immediately next to an air quality monitoring reference station and carrying out regression analysis of AQMesh readings against those from the RTMS, where a higher R2 shows a closer match in readings from the two types of equipment (an R2 value of 1.0 is a perfect relationship, and is unlikely to be achieved even by two co-located reference instruments; R2 of 0.0 would indicate no relationship at all between the instruments).
The table below shows that the R2 value achieved has shown a significant improvement from v.3.0 and v.4.2:
|Date||To December 2014||January 2015 – October 2015||January 2015 – October 2016||Limited release||October 2016 – present|
|NO2 sensor||Significant O3 cross-gas effect||O3-filtered||O3-filtered||O3-filtered||O3-filtered and improved response at higher ambient temperatures|
|NO2 sensor characterisation||Manufacturer’s data||Manufacturer’s data||Manufacturer’s data plus characterisation at factory||Quality check||Quality check, accuracy and precision tests|
|Online processing||Correction for cross-gas effects and environmental factors||Correction for cross-gas effects and environmental factors||Correction for cross-gas effects and environmental factors||More sophisticated correction for cross-gas effects and environmental factors||Optimised electronic set-up and performance enhancements below LOD|
|Typical R2 against reference in co-location trials*||0-0.3||0.1-0.7||0.5-0.8||0.7-0.95||>0.8|
|Typical pre-scaled mean variance*||Requires scaling||Requires scaling||Requires scaling||Dependent on variance between sensors||<+/-5ppb|
R2 of >0.6 for NO2 is generally considered to be a strong enough performance for AQMesh to be suitable for most air quality monitoring applications.
*Readings at 15 minute average intervals
A number of independent comparison studies have been published online – please note any date / AQMesh version against the table above to establish whether the study relates to the latest version.
Standard operating procedure
The standard operating procedure provides users with all the necessary information to get the best possible performance with AQMesh.