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34 

ObservAir

 Operating Manual 

5.4.

 

Operational settings for common applications 

 
Table  9  provides  typical  BC  concentrations  and  operational  settings  for 
some  common  sampling  scenarios.  Note  that  the  guidance  provided  is 
approximate  and  mostly  meant  to  serve  as  an  illustrative  guide:  Some 
applications may not be well described/served by the parameters listed.    
 

 

 

Table 9. 

General settings for several monitoring applications 

 

 

Ambient monitoring: 

When deploying the ObservAir as a static network 

node over long periods (weeks or months), the flow rate should be set 
as low as possible to maximize filter life and reduce the maintenance 
effort, especially when network sites are remote or numerous. Ambient 
monitoring  applications  typically  require  data  with  low  temporal 
resolution – hourly measurements are often sufficient – and this helps 
reduce the flow rate requirements. Referring to Table 8, it can be seen 
that the minimum flow rate setting of 25 ccm provides suitable hourly 
measurements for nearly all BC concentrations. However, it should be 
noted that this achieves a nominal BC measurement resolution that is 
~10% of the average concentration, which may not be sufficient for all 
applications (e.g., regulatory monitoring). If greater resolution is desired, 
flow rate should be increased to the values listed in Table 9. Similarly, 
special  consideration  should  be  given  when  conducting  long-term 
monitoring  in  rural  or  remote  areas  with  BC  concentrations  <  0.5 

µ

g/m

3

.  In  these  scenarios  when  filter  loading  is  low,  it  is  generally 

advisable to operate the sensor at a high flow rate setting (100 to 200 
ccm) to maintain BC measurement integrity.  

Average BC  

(

µ

g/m

3

Flow rate 

(ccm)

Time 

Resolution

Filter life

Ambient: 

Background/rural

Low            

(0 to 1)

High       

(100 to 200)

Low         

(1 hour)

High  

(Weeks/Days)

Ambient:         

Typical

Medium         

(0.3 to 5)

Medium    

(50 to 100)

Low         

(1 hour)

High  

(Weeks/Days)

Ambient:          

Dense Urban

High           

(5 to 50) 

Low         

(25 to 50)

Low         

(1 hour)

Medium   

(Days)

Emissions capture 

(direct source)

Extreme         

(> 100)

Medium     

(50 to 100)

Medium      

(10 to 60 sec)

Very low 

(Hours)

Mobile/Personal

Medium/High    

(0.3 to 50) 

High       

(100 to 200)

High         

(2 to 10 sec)

Low          

(1 day)

 

 

35 

ObservAir

®

 Operating Manual 

 

 

Emissions source characterization: 

The ObservAir can be configured to 

characterize emissions from stationary 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 ratings (Table 3). As with other instruments, 
the ObservAir may require that emissions from the source be diluted, 
cooled,  and/or  dried.  For  transient  monitoring  applications,  such  as 
engine  testing,  measurements  are  typically  required  every  2  to  10 
seconds, and therefore the ObservAir’s sample flow rate must usually 
be set >100 ccm to maintain adequate measurement resolution. When 
sampling over long periods (stack monitoring over hours or days), the 
sample flow rate may be lowered to 25 or 50 ccm to maximize filter 
life,  especially  when  concentrations  are  highly  elevated.  Sampled 
concentrations  depend  on  the  source  and  flow  conditioning  system 
implemented (e.g. diluter), but it is not unusual for BC concentrations 
to exceed 100 

µ

g/m

3

 when capturing emissions directly.  

 

 

Mobile  monitoring: 

When  sampling  from  a  mobile  platform, 

measurements must be logged as fast as possible to maintain adequate 
spatial resolution required for the air pollution maps that are ultimately 
generated.  Therefore,  the  ObservAir  should  be  configured  to  log 
concentration  data  every  2  to  10  seconds  at  the  maximum  flow  rate 
setting of 200 ccm to maximize the temporal resolution of both BC and 
gas concentration measurements. Always operate the ObservAir inside 
the  mobile  platform  (e.g.  car  or  van)  with  an  electrically  conductive 
sample line running outdoors. Do not mount sensors on the exterior of 
mobile  platforms  without  the  dedicated  DST  mount  and  enclosure. 
When mounting the ObservAir inside the mobile monitoring platform, 
take care to minimize exposure to mechanical vibrations, excessive heat 
and/or direct sunlight over extended periods.   

 

 

Personal  monitoring: 

Personal  monitoring  guidelines  largely  mirror 

those provided for the mobile platform: Operate the sensor at a high 
sample  flow  rate  (100  to  200  ccm)  to  maximize  the  quality  of  BC 
measurements  collected  every  2  to  10  seconds.  Depending  on  the 
application  and  concentrations  sampled,  some  consideration  may  be 
given optimizing the flow rate for filter life (e.g., each filter lasts a full 8-
hour  workday).  The  sensor  may  be  mounted  inside  a  bag  or  from  a 
strap  (such  as  those  provided  by  DST),  but  take  care  to  clip  an 
electrically  conductive  sample  line  to  the  subject’s  lapel  or  other 
appropriate location. 

 

 

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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