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DST ObservAir Operating Manual

Distributed sensing technologies
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ObservAir
Operating Manual
Distributed Sensing Technologies
Released: November 1, 2020
Version: 1.0
© 2020 Distributed Sensing Technologies, LLC

Table of Contents

1.
Introduction .............................................................................................. 3
1.1.
Principle of operation .................................................................................... 4
1.1.1.
Aerosol absorption photometer (Black carbon) ............................ 4
1.1.2.
Electrochemical cells (Gaseous pollutants) .................................... 6
1.2.
Environmental compensation .................................................................... 7
1.3.
Base package contents ................................................................................. 8
2.
Technical Specifications ......................................................................... 9
2.1.
General specifications ................................................................................... 9
2.2.
Measurement performance ..................................................................... 10
2.3.
Operational limits and warnings ............................................................ 11
3.
Operating Instructions .......................................................................... 13
3.1.
Hardware overview ....................................................................................... 13
3.2.
3.2.1.
Sensor startup .......................................................................................... 15
3.2.2.
3.2.3.
Sensor menu Interface ......................................................................... 15
3.2.4.
Attenuation reset ..................................................................................... 16
3.2.5.
Sensor shutdown ..................................................................................... 16
3.2.6.
Sensor alarms and errors .................................................................... 16
3.3.
Filter tab replacement ................................................................................ 17
3.4.
Battery charging ........................................................................................... 18
3.5.
Data collection from onboard SD card ............................................... 19
3.5.1.
Settings file ................................................................................................ 19
3.5.2.
Data file ....................................................................................................... 21
3.6.
Computer (serial USB) connection ....................................................... 22
3.6.1.
Connecting to Arduino Serial Monitor ............................................ 22
3.6.2.
Serial data collection ............................................................................. 23
3.6.3.
Sensor configuration: Serial commands ....................................... 23
3.7.
WiFi connection ............................................................................................. 25
3.8.
Firmware updates ........................................................................................ 26
1
ObservAir
®
Operating Manual

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Summary of Contents for DST ObservAir

  • Page 1: Table Of Contents

    ObservAir Table of Contents Introduction ....................3 1.1. Principle of operation ..................4 1.1.1. Aerosol absorption photometer (Black carbon) ......4 Operating Manual 1.1.2. Electrochemical cells (Gaseous pollutants) ........6 1.2. Environmental compensation ..............7 1.3. Base package contents ................. 8 Technical Specifications .................

  • Page 2: Introduction

    The ObservAir is designed to be easily deployed anywhere, and trusted to deliver accurate air quality measurements reliably and conveniently. If you have any questions about integrating the ObservAir into your air quality monitoring efforts, please contact us at info@dstech.io.

  • Page 3: Principle Of Operation

    Optical attenuation (ATN) is defined in terms of the two light intensity configured to measure concentrations of black carbon (BC). BC is a type of measurements, as shown below. In the ObservAir, both measurements are particulate matter (PM) pollution generated by the incomplete combustion reported as the bit count from the photodiodes’...

  • Page 4: Electrochemical Cells (Gaseous Pollutants)

    The Mass Absorption Coefficient (MAC) is a calibration factor that relates ObservAir for 12 to 24 hours in an environment that is free of the analyte the time differential of ATN to BC concentrations in the flow. The MAC varies gas(es) and average the voltage differential data collected over the entire depending on the air pollution source, PM composition and other factors.

  • Page 5: Base Package Contents

    Each by the manufacturer, and where possible, DST validation of the ObservAir is delivered with its own unique zero-calibration sheet, as shown electrochemical cells in the ObservAir platform. All baseline measurement in Figure 3 below.

  • Page 6: Measurement Performance

    Moisture/rain: Even when fitted with the weatherproof cover, the • ObservAir must not be directly exposed to rain or moisture of any kind without an appropriate DST enclosure. When fitted with external sampling lines, these must be fitted with rain covers or water catches to ensure that water is not aspirated into the sensor.

  • Page 7: Operating Instructions

    Positive pressure air in the sensor can damage The ObservAir is shown in Figure 4 below. The sample air inlet and outlet sensing elements and other hardware.

  • Page 8: Interactive Led Button: Sensor Display And Control

    Each ObservAir comes with a magnetic cover, shown in Figure 6, that 3.2.1. Sensor startup mounts to the front panel and covers the USB port, SD card slot, and filter To turn on the sensor, press and hold the button for 5 seconds until the tab to protect the sensor from moisture and dust penetration.

  • Page 9: Attenuation Reset

    ATN will be set to zero for the current light intensity values. 3.2.5. Sensor shutdown To turn off the ObservAir, hold the LED button to cycle through the menu until the first red flash and release. The sensor will flash red two more times to confirm that it is shutting down.

  • Page 10: Battery Charging

    3.5. Data collection from onboard SD card While the ObservAir is operating, data is written to the onboard SD card in real time as both a primary means of data collection and a reliable physical backup when wireless data transmission protocols are implemented. By default, the ObservAir creates a new data file every time it starts up.

  • Page 11: Data File

    3.5.2. Data file ObservAir unit. Most factors in this field are for DST’s internal protocols, The ObservAir data is written in comma separated value (csv) format to a but those pertinent to the end user are listed below: .txt file. Each line in the file represents a datalogging event, and starts with a.

  • Page 12: Computer (Serial Usb) Connection

    3.6. Computer (serial USB) connection The ObservAir can stream data and receive commands via a USB serial connection to a computer. While any serial monitor may be used to communicate with the sensor, we recommend the free and open source Arduino Serial Monitor for the basic operations outlined in this manual.

  • Page 13: Wifi Connection

    $ATNreset$ Reset the attenuation (ATN) to 0 4. A captive portal (Figure 13) will appear requesting your WiFi network’s SSID and password. The ObservAir is only compatible with 2.4 GHz WiFi BC, GAS1, Set the LED to pollutant concentration networks.

  • Page 14: Firmware Updates

    In this configuration, the receive the update. flow rate of zero air is set slightly higher than the ObservAir inlet flow, and a. If a unit is unable to connect to a WiFi network, it will automatically the excess zero air is vented to the atmosphere through a purge on the reboot into WiFi provisioning mode and breathe blue.

  • Page 15: Flow Rate Calibration

    O over 60 seconds. If the sensor meets or exceeds this criterium, it has passed 1. Turn on the ObservAir and allow it to warm-up for at least 15 minutes. the leak check and may be deployed. 2. Connect ObservAir to a serial monitor (Section 3.6).

  • Page 16: Best Practices

    ATN values. Therefore, it is best practice to only 2. Jimenez, J.; Claiborn, C.; Larson, T.; Gould, T.; Kirchstetter, T. W.; operate the ObservAir while the optical ATN is < 80, and replace the filter Gundel, L. Loading Effect Correction for Real-Time Aethalometer when this threshold value is exceeded.
  • Page 17 (1) searching the literature or regulatory databases for representative BC concentration data, or (2) conducting preliminary Data logging period testing with the ObservAir at a flow rate setting of 100 ccm. The logging 2 sec 15 sec 1 min 1 hour interval is dictated by the application context and goals.

  • Page 18: Operational Settings For Common Applications

    The sensor may be mounted inside a bag or from a monitoring in rural or remote areas with BC concentrations < 0.5 strap (such as those provided by DST), but take care to clip an . In these scenarios when filter loading is low, it is generally µg/m...

  • Page 19: Indoor/Outdoor Monitoring Guidelines

    LED button, and will for the ObservAir to leak or for the flow rate sensor’s output to drift trigger a hard reset when exposed to the magnets in the cover. When a hard...
  • Page 20 Figure 14. Hard reset using the magnetic cover ObservAir Operating Manual...

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