User's Manual

Averages and MAD's at one minute sample rates are comparable to those taken at any
other sample rate.
Additionally, the accelerometers can record peak counts. Peaks are points in the
accelerometer signal where acceleration has reached its highest point relative to the
samples immediately surrounding it. The point sample channels allow the experimenter
to record all accelerometer samples acquired at 32 samples per second.
The Armband measures several basic physiological quantities in the various ways
described above. Below are descriptions of each of these physiologic measures.
Accelerometer
• Description: An accelerometer measures motion forces exerted on the body in a
single plane. Static and dynamic forces are measured in two perpendicular axes:
longitudinal which is parallel to the arm and transverse which is perpendicular to
the arm.
• Channels: There are a total of 8 accelerometer channels. They are:
1. Transverse Accelerometer - point
2. Transverse Accelerometer - peak
3. Transverse Accelerometer - average
4. Transverse Accelerometer - MAD
5. Longitudinal Accelerometer - point
6. Longitudinal Accelerometer - peak
7. Longitudinal Accelerometer - average
8. Longitudinal Accelerometer MAD
• Technology: The accelerometer is a 2-axis micro-electro-mechanical sensor
(MEMS) device that measures motion.
• Units: Meters per second squared relative to earth gravity. For example, a data
reading of 1 is one earth g, or approximately 9.8 meters per second squared
(m/s²).
• Calibration: Two known orientations.
• Scenario: The accelerometer MAD is a measure of stillness and movement. For
example, while sitting still watching a movie, the accelerometer MAD values will
be near zero, but while jogging the accelerometer MAD values will be high. The
accelerometer average is a measure of both acceleration and orientation relative to
the ground. For example, a sleeping person may not be moving, but can still
register 1g acceleration due to gravity. On a roller coaster, a person may be
subject to higher than normal average accelerations. The peaks summary is related
to the frequency of vibration to which the wearer is subjected. An Armband worn
by the person riding the roller coaster will record large counts in the peaks
channel whereas the sleeper will likely generate values near zero.
Heat Flux