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6
G
ENERAL FEATURES
6.1 Operating principles
6.1.1
The
Always on
principle
The FDL Mini
is “Always on” meaning that w
henever it has power (from external supply or
internal battery) and the “
Off-dongle
” is not connected, it will log data using the settings last
specified by the user.
6.1.2
File creation
The FDL Mini will keep logging data to a file until a new file is created. A new file is created
when:
•
The FDL Mini
is switched off and turned on again (e.g. mounting the “
Off-dongle
”
for
5 seconds and removing it again. Wait 30 seconds before connecting to a PC)
•
The internal time setting of the FDL Mini is changed
•
The FDL Mini sampling rate is changed
•
STOX support is either enabled or disabled for one of the data channels
6.1.3
Download of data
The data can be downloaded at any time from the FDL Mini using the SensorTrace Logger
software. Downloading data will not interrupt the data logging process. The FDL Mini will
continue to store data in the same file and append it to the data that are already stored.
Therefore, when data is downloaded at the end of a deployment the file will contain all data
from that deployment. Downloading data during a deployment can be used as a sneak peek
to see how things are going.
6.1.4
Data calibration
Data are recorded uncalibrated in the FDL Mini. Calibration is performed after download of
data to the SensorTrace Logger. Each sensor must be calibrated before or after the
deployment. This calibration is imported into the data file retrieved from the FDL Mini and
applied to the data retrieved from the FDL Mini.
6.2 Support for STOX sensors
Sensor channels with built-in amplifiers support the use of STOX sensors for measuring
extremely low O
2
concentrations. The timing and the polarization for the on/off cycles of
the front guard can be set individually for each channel. The data file will contain both the
signal for oxygen concentration and a signal indicating whether the front guard polarization
is on or off.
6.3 Sensor connections
At the time of ordering it is decided for each channel whether the amplifier is internal or
external. With internal amplifier the sensor is mounted directly on the bulk-head connector