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26 

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 

[email protected]

.  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.   

 

 

27 

ObservAir

®

 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 

[email protected]

 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.  

Содержание ObservAir

Страница 1: ...rational limits and warnings 11 3 Operating Instructions 13 3 1 Hardware overview 13 3 2 Interactive LED button Sensor display and control 14 3 2 1 Sensor startup 15 3 2 2 Default LED mode Pollutant c...

Страница 2: ...pport WiFi and USB communication protocols and include a 16GB removable SD card for onboard data storage Units may also be supplemented with an LTE LoRa or SigFox communication module and a GPS unit f...

Страница 3: ...collection area is 3 mm in diameter After the first filter the air flow passes through a second reference filter assembly that is identical to the first Since the air is filtered devoid of PM the int...

Страница 4: ...plication Operate the 7 ObservAir Operating Manual ObservAir for 12 to 24 hours in an environment that is free of the analyte gas es and average the voltage differential data collected over the entire...

Страница 5: ...technical specifications are summarized in the tables below All electrochemical cells are sourced from Spec Sensors Gas measurement performance specifications are adapted from data provided by the ma...

Страница 6: ...intervals 2 3 Operational limits and warnings Environmental limits Only operate the ObservAir within the conditions listed in Table 1 Temperature and relative humidity must remain between 5 to 40 C an...

Страница 7: ...nd may result in permanent damage to the unit and or harm to the user Please contact DST Technical Support at info dstech io regarding any problems with your unit that cannot be resolved with the inst...

Страница 8: ...llutants For every new start up event a new data file is created on the SD card txt file and is assigned a filename that contains the sensor s ID number and the start up time date Section 3 5 1 3 2 2...

Страница 9: ...f 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 3 2 6 Sensor alarms and...

Страница 10: ...ront panel 19 ObservAir Operating Manual 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 c...

Страница 11: ...e ADC s raw count Full scale value is 8388607 d ATN Optical attenuation unitless e BC Black carbon in g m3 f T Temperature in C g RH Relative humidity in h FR Sample flow rate in ccm i VBAT Battery vo...

Страница 12: ...tings Figure 12 6 With the Serial Monitor configured ObservAir data is displayed in real time at the time interval set by the user Commands can also be sent to the sensor using the dialog box at the t...

Страница 13: ...8 to 1 2 Set flow rate calibration coefficient Table 7 ObservAir serial commands and descriptions 25 ObservAir Operating Manual 3 7 WiFi connection Provisioning WiFi credentials to the ObservAir allo...

Страница 14: ...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...

Страница 15: ...but clearly the calibration is only as good as the reference measurements collected 4 4 Leak check The ObservAir incorporates a monolithic design architecture that is more robust than traditional ins...

Страница 16: ...loading artifact is not static it depends on the emissions source e g biomass vs diesel atmospheric conditions seasonality and other factors Therefore filter loading correction algorithms should be c...

Страница 17: ...ing can be optimized to meet your needs For example if greater BC measurement resolution is desired at the expense of filter life the flow rate can be increased past the minimum value Conversely flow...

Страница 18: ...exhaust stacks vehicle tailpipes and other pollution sources When sampling emissions directly do not exceed the ObservAir s maximum temperature relative humidity range and pollution concentration rat...

Страница 19: ...If BC measurements are proportionally lower than the reference value then it is also possible but less likely that the ObservAir is leaking Given these potential error modes it is important to valida...

Страница 20: ...38 ObservAir Operating Manual Figure 14 Hard reset using the magnetic cover...

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