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ObservAir
Operating Manual
3.8.
Firmware updates
As we continue to make improvements and introduce new features, new
versions of the firmware will be released using over-the-air (OTA) updates.
Please follow the instructions below to update your unit(s) firmware.
1.
Setup an update appointment by emailing
. Please
include the phrase “OTA Update: SN” where SN represents your unit(s)
serial number(s).
2.
Provision the unit(s) with your WiFi network’s credentials according to
the instructions provided here (Section 3.7).
3.
During the time period scheduled with our team, turn on your ObservAir
unit(s) and cycle through the menu interface until the LED flashes
purple twice (OTA firmware update mode).
4.
The ObservAir will restart into OTA firmware update mode, and breathe
purple once it is successfully connected to the internet and ready to
receive the update.
a.
If a unit is unable to connect to a WiFi network, it will automatically
reboot into WiFi provisioning mode and breathe blue. Follow steps
3 to 5 in Section 3.7 to provision WiFi credentials.
5.
With the LED breathing purple, plug the unit(s) into the wall charger
and wait for the units to receive the update.
a.
If no update is received, OTA update mode will automatically turn
off and restart after 12 hours if no update has been applied. Please
check that your unit is on during the appointment scheduled with
DST staff.
6.
After firmware update is received and applied, the sensor will blink
purple three times to confirm that the update was successful and will
then restart into the normal operating mode.
7.
Turn off the unit(s), and remove the SD card to read the Settings file. In
the ‘Sensor Settings’ section, check that the ‘Firmware’ field has been
updated to the latest version (version number will be provided while
scheduling appointment with DST staff).
3.9.
External sample lines
The ObservAir can be fitted with external sample lines that extend outside
an enclosure and/or pull air directly from a flow conditioning device (e.g. a
diluter or dryer). Sample lines should be made of soft rubber tubing with
an inner diameter (ID) of 3/32 inch, such that they fit snuggly over the
nozzles (1/8-inch outer diameter). Inlet lines must be electrically
conductive to prevent particle loss. McMaster-Carr part numbers
1909T3
and
5648K23
may be used for the inlet and exhaust lines, respectively.
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ObservAir
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Operating Manual
4.
Maintenance and Calibration Procedures
4.1.
Zero calibration of pollution sensors
Each ObservAir comes with a zero-calibration sheet, but it is good practice
to periodically verify the sensor’s baseline performance, especially before
and after deployments. To zero calibrate the BC sensor, an inline HEPA filter
(collection efficiency must be >99%) may be fitted on the inlet nozzle such
that no PM is sampled. DST distributes inlet filters for calibration, but HEPA
filters widely available for homebrewing are also typically adequate for this
purpose. If zero calibrating gas sensors, it is best practice to get a cylinder
of zero air (calibration gas that is devoid of any analyte species). To
conserve zero air, the ObservAir can be operated in a closed volume that is
filled with zero air: A high-quality Tupperware can easily be outfitted with
inlet/outlet valves for this purpose. Alternatively, the ObservAir may sample
a controlled flow rate of zero air from the cylinder. In this configuration, the
flow rate of zero air is set slightly higher than the ObservAir inlet flow, and
the excess zero air is vented to the atmosphere through a purge on the
sample line. This open system prevents pressurization of the ObservAir,
which can damage the sensor. Whichever calibration configuration is
chosen, the ObservAir should collect zero concentration data every 2
seconds for at least 24 hours at the desired flow rate setting. Using the 2-
second data collected, it is possible to determine the pollution sensors’
baseline noise levels at various measurement time intervals (1 minute, 1
hour, etc.). DST can also zero-calibrate ObservAir units, please contact
for information on our calibration services.
4.2.
Span calibration of pollution sensors
Span calibration of the ObservAir is not straightforward, particularly since
no calibration standards exists for BC. Typically, the best and most practical
method of span calibration outside of a dedicated laboratory or research
setting is collocation at a regulatory monitoring station. Using your local
environmental protection agency’s website (e.g.,
airnow.gov
in the US),
locate an air quality monitoring station near you, and deploy your sensor(s)
as close by as possible (<1 km in all cases, but < 50 m is best). Depending
on the agency, it may be possible to contact your local branch or
representative and ask about collocation opportunities. In most cases, the
ObservAir can simply be left outside near the station for 24 hours with little
to no setup (no plug or connection required). Compare the data collected
by the ObservAir to that collected simultaneously at the regulatory station
and calibrate/adjust accordingly.