USER MANUAL
STM 550 / EMSI
–
ENOCEAN MULTISENSOR FOR IOT APPLICATIONS
© 2020 EnOcean | www.enocean.com F-710-017, V1.0
STM 550 / EMSI User Manual | v1.3 | September 2020 | Page 83/97
11.3
Acceleration sensor
Acceleration sensors measure the acceleration vector in all three dimensions {x; y; z}. This
sensor can be used both to determine the device orientation (relative to the earth gravity
vector) and the device acceleration (e.g. if a device is moved or shaken). Both cases will be
discussed below.
11.3.1
Device orientation use cases
If an object is at rest or continuously moving at the same speed, then the magnitude of the
vector will be 1g (i.e. the magnitude of the measured acceleration vector will be equivalent
to the magnitude of the earth gravity vector at the location of the device which will be ap-
proximately 1g).
Measuring the magnitude in all three dimensions allows determining the orientation of an
object relative to the earth gravity as shown in Figure 62 below. This illustration assumes
that STM 550 is placed flat onto a surface parallel to the earth surface (e.g. a table).
Figure 62
–
Acceleration vector based on device orientation
Note that it is not possible to distinguish cases where STM 550 is rotated but its orientation
relative to the direction of earth gravity remains the same. This is shown in Figure 63 below
for the case of device rotation across the earth gravity vector axis.
Figure 63
–
Device rotation across earth gravity vector axis