USER MANUAL
STM 550X / EMSIX
–
ENOCEAN MULTI-SENSOR
© 2020 EnOcean | www.enocean.com F-710-017, V1.0
STM 550x / EMSIx User Manual | v1.0 | February 2020 | Page 75/79
9.2
Acceleration detection
Acceleration detection enables to track the utilization of an asset (is a machine running, is a
chair occupied, …) based on the characteristic vibrations associated with this
utilization.
Acceleration sensors
–
unlike gyroscopic or compass sensors
–
work based on changes of the
acceleration vector. When an acceleration sensor (i.e. STM 550x) is at rest then the acceler-
ation vector is the gravity vector of the earth. Changes in asset orientation (e.g. measuring
the tilt of a window to distinguish between open and closed state) can therefore only be
detected if the orientation of STM 550x relative to the gravity vector changes.
Figure 55 below illustrates two cases:
◼
The position of the window in the left case (window tilt) could be detected if STM
550x is attached to the window part that is tilted since the orientation of STM 550x
relative to the gravity vector would change
◼
The position of the window in the right case (window open / rotation) could not be
detected if STM 550x is attached to the window part that is rotated since the orien-
tation of STM 550x relative to the gravity vector would remain the same.
STM 550x would however report that the window was moved due to the resulting
acceleration and deceleration.
The surface towards which STM 550x is attached should therefore be chosen to maximize
orientation changes relative to the gravity vector.
Gr
av
ity
Gr
av
ity
Figure 55
–
Tilt versus gravity vector
