4
Shock sensor
The fusionTrack device is equipped with a shock detection circuitry, hereafter called shock sensor. The
shock sensor is a very low power, battery powered electronic unit designed by Atracsys based on a mi-
crocontroller (
µ
C). The unit is composed of three accelerometers, a temperature sensor, a real time clock
(RTC) and a non-volatile memory. Two of the three accelerometers are continuously monitoring shocks that
might happen to the tracking system and the third one is providing the device orientation. Additionally, the
shock sensor also records information about the use of the tracking system, such as the number of boot
or the usage time.
The primary purpose of the shock sensor is to detect and record shocks encountered by the tracking
system above a certain threshold, actually set to
100
g
, where
g
=
9
.
81 m s
−
2
is the average Earth gravi-
tational constant. Thanks to the built-in rechargeable battery, theses shocks are recorded even when the
tracking system is not powered. Each shock event is timestamped by the real-time clock. If such a shock
event over the threshold has happened, the user is informed over the SDK if the corresponding option is
activated.
The battery is automatically recharged each time the fusionTrack device is powered. Therefore, in a
regular usage scenario, the battery is always (almost) fully charged. A completely empty battery is fully
recharged in 24 h. The system runs autonomously for approximately 6 months without recharging the
battery. In case the battery runs out of power, the shock sensor will be safely stopped and, thanks to the
non-volatile memory, the recorded data stays saved. Shocks that might happen during the time where the
shock sensor has an empty battery are of course not logged anymore. The user however is informed, if
the battery runs out and therefore non-recorded shocks might have happened. In such an empty battery
event, to validate the accuracy of the tracking system, Atracsys recommends to run an AVT analysis (see
Chapter 13).
The fusionTrack device should be recharged for 24 h, if it is
stored for 6 months.
4.1 Registers
An error registers and a status register are accessible using the
atnet64
software, using the
info_uC *
command.
4.1.1 Status register
Bit
7
6
5
4
3
2
1
0
Reserved Reserved No bat-
tery
Reserved Reserved Reserved Reserved Enabled
21
