18
ObservAir
Operating Manual
s
Figure 10.
Step 3 of filter tab replacement: Push the filter tab into the
sensor until it is fully seated (notch should be flush with front panel) and
tighten the thumbscrew firmly.
It is best to change the aerosol filter while the ObservAir is powered off.
However, if this is not possible or inconvenient, the filter may also be
changed while the sensor is running. In this case, the LED button will flash
red rapidly while the filter is removed to indicate that an error is occurring.
When the filter is replaced and tightened, the LED will go back to normal
breathing mode, indicating current pollutant concentrations. If the LED
flashes red rapidly after replacement, check that the filter tab has been
inserted fully into the sensor and is properly aligned in the slot: The notch
on the tab should be directly above the solid white circle and flush with the
front panel. The sensor will automatically detect the new filter and reset the
ATN to 0. The ATN can also be reset manually (Section 3.2.4).
3.4.
Battery charging
Whenever possible, the ObservAir’s internal battery should be recharged
using the included micro-USB cable and 2.1A power adapter. The sensor
charges fastest when it is powered off and connected to the 2.1A power
supply: a depleted battery will fully charge in about 5 hours in this
configuration. When the sensor is off and charging, the LED button shines
a solid and turns off when charging is complete. The sensor can also be
plugged into the charger while it is powered on and operating. The battery
will automatically recharge in this state, but at a lower charging current
than when the sensor is powered off. When in normal operation, the LED
button will briefly flash yellow once to indicate that a charging cable has
been successfully connected. The sensor will also trickle charge while
connected to a computer’s USB port.
Filter notch aligned with solid white mark.
Notch tip flush with front 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 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. Each
file
represents
a
data
collection
“mission”,
and
is
called
“DataXXX_YYMMDD_HHhMMm.txt” where XXX represents the ObservAir
unit’s ID, followed by the date and time of startup. The SD card also
contains a file called “Settings_DataXXX.txt” (where again XXX represents
the unit’s ID) that contains a running log of the sensor’s operational
settings. A comprehensive overview of both files’ contents is provided below.
3.5.1.
Settings file
For each sensor mission, a new entry is appended to the settings file with
the corresponding data file name as the header. Each entry in the settings
file is composed of four sections:
1.
Header:
The name of the corresponding data file for which the listed
sensor settings apply.
2.
Sensor Settings:
This field contains information on the sensor’s
configuration and operational settings. Fields are defined below and
appear in the order listed.
a.
SN
Serial number.
b.
ID:
User assigned sensor ID. Default is the unit’s SSN.
c.
Version:
Hardware version number.
d.
Firmware:
Firmware version number.
e.
GAS1:
First optional gas sensor mounted onboard.
f.
GAS2:
Second optional gas sensor mounted onboard.
g.
flowRate:
Sample flow rate setting in units of ccm. Default is 100
ccm.
h.
samplePeriod:
The data collection sample rate in seconds. Default
setting is 2 seconds.
i.
envComp:
DST’s proprietary environmental compensation
algorithms are active (‘True’) or pollution concentration
measurements are direct from the sensor(s) and uncompensated
(‘False’). Default setting is True.
j.
DLPFilter:
Digital low pass (DLP) filter is active (‘True’) or turned off
(‘False’). The DLP filter decreases measurement noise but increases
the minimum 90% response time from ~2 to 8 seconds when
monitoring BC concentrations. Gas measurement response time is
minimally affected. Default setting is True.