Low Frequency Extension; Data Collection - ActiGraph wGT3X+ User Manual

stillness for three (3) minutes indicates that the unit is likely in an "off" condition regardless of
orientation. As such, epochs that follow three motionless minutes of activity are flagged as "off," i.e.,
the inclinometer code is equal to zero. These values are not retroactive. That is, the first three minutes
of zero activity are not flagged as "off." In addition, 30 minutes in the "off" orientation will cause the
inclinometer value to indicate off after that time period has elapsed regardless of motion.
At this time, the inclinometer feature is being validated by the research community.

Low Frequency Extension

The Low Frequency Extension (LFE) option, though not a mode or channel, is another data collection
option during device initialization, and during post-processing for the wGT3X+ and wActiSleep+. The
Normal proprietary filter algorithm used in ActiGraph products is used to eliminate any acceleration
noise outside of the normal human activity frequency bandwidth. This filter is customized to work with
ActiGraph's Energy Expenditure
(baseband) of the filter cutoff, effectively expanding the bandwidth of the accumulated data. This
option is useful when measuring actigraphy data for subjects who move slowly or take very light steps
(for example, the elderly). For more details, contact ActiGraph at support@theactigraph.com.

Data Collection

During initialization, the user chooses the raw data sample frequency (30Hz up to 100Hz in 10Hz
increments). The wGT3X+ and wActiSleep+ collect data from all on-board sensors in raw data format.
Data recorded includes:

Vertical Axis Activity Acceleration Data (Axis 1)

Horizontal Axis Activity Acceleration Data (Axis 2)

Perpendicular Axis Activity Acceleration Data (Axis 3)

Ambient Light (Lux)
Although Steps and Inclinometer are not directly measured during data collection,
these values can be derived from the 3-axis data during *.gt3x file
decompression.
Unlike previous ActiGraph products, the wGT3X+ and wActiSleep+ do not filter or accumulate data into
epochs. Raw data is collected at the selected sample rate and is post-processed in the ActiLife. Because
these devices collect data from all sensors at all times, users can generate native ActiLife *.agd files
containing any desired combination of parametric data at a later time. This helps facilitate backward
compatibility and enhances the flexibility of the data by allowing users to compare data to studies which
use different filter techniques or accumulation sizes (e.g., 1 second epochs versus 60 second epochs).
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Algorithms. The LFE option, when enabled, extends the lower end
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