Building-block sensor
The building-block (Lego) sensor is a hands-on teaching module that illustrates how light scattering can be used to detect particle pollution.  It cannot detect atmospherically relevant levels of pollution. 

AirU package
The AirU package will be distributed to Salt Lake County schools, beginning in the Fall of 2017.  AirU can measure relevant levels of particle and carbon monoxide pollution.   It contains sensors for:

  • Temperature and relative humidity with a HDC 1080 sensor (Datasheet).
  • Intensity of Visible Light with an OPT3001 (Datasheet).
  • CO and NO2 with a SGX Sensor Tech MiCS-4514 (Datasheet). This is a metal-oxide based sensor.
  • GPS location with the Adafruit Ultimate GPS Module, based on the FGPMMOPA6H chip from GlobalTop Technology (Datasheet).
  • Particulate matter (PM) with a Plantower PMS 3003 laser particle counter (Datasheet).   It uses a fan to draw air through a chamber where it is exposed to a laser-induced light, and 90o scattered light is detected by a photo-diode detector.  According to the manufacturer, it detects PM in the range of 0.3 um to 10 μm, and it has a 10-second response time. The sensor converts light scattering to PM1, PM2.5 and PM10 concentrations. We estimate the laser wavelength at approximately 650.  See our paper evaluating the performance of this sensor.
  • Location with an Adafruit Ultimate GPS (Datasheet).

At the core of the AirU is a secure WiFi certified CC3200MOD microcontroller. This system uses an IoT development platform that requires no prior hardware knowledge to provide the end user with a remote monitoring via a website. Backup data is stored to a micro SD card. If wifi is available each AirU station will push data to the website. If it is not available, the AirU will store data to the on-board microSD card. If wifi becomes available, AirU will push the data to the online database. The air-quality information is written to a CSV file with a file name of the form "m-d-Y.csv".

Sensor Calibration
Because low-cost sensors can perform inconsistently, we are evaluating PM sensor performance in three different ways:

  • Co-locating the PM sensor with federal reference methods at Utah Division of Air Quality’s Hawthorne monitoring station (Kelly et al) during a variety of different pollution events including winter-time inversions, fireworks, and wildfires.
  • Evaluating sensor performance in the field.
  • Calibrating the PM sensors in an aerosol chamber with two different types of test particles, ammonium nitrate and alumina oxide. The chamber tests eight PM sensors and a reference sensor. This cylindrical chamber was designed to maximize the uniformity of particle concentration.
airu-board
Our current sensor design
Side view of the aerosol calibration chamber
Aerial view of the aerosol calibration chamber
COMSOL simulation of particle distribution inside the aerosol calibration chamber