W
IRELESS
H
IGH
-P
RECISION
T
ILT
S
ENSOR
C
OPYRIGHT
©
2019,
R
ADIO
B
RIDGE
I
NC
.
W
IRELESS
H
IGH
-P
RECISION
T
ILT
S
ENSOR
P
AGE
8
OF
15
The report-on-change messages are sent when the tilt angle increases away from vertical or
decreases back to vertical a specified amount from the last report. For example, consider a
report-on-change value that is set to 5 degrees and the current angle from the vertical axis is
15 degrees. If the angle increases to 20 degrees an 0x04 event is sent. If the angle decreases
back to 15 degrees, an 0x03 event is sent.
6.2.1.
Temperature Compensation
The temperature reported in byte 0x03 of the uplink message is a two’s compliment
signed integer value representing the ambient temperature inside the sensor in degrees
C. This is reported because MEMS-based accelerometers are sensitive to temperature and
thus skew the tilt angle at temperatures significantly above or below room temp.
If tilt precision under 1 degree is required and the sensor is not at or near room
temperature (25 degrees C), then the temperature output can be used to further calibrate
the device. A temperature dependence curve is shown below at an orientation of 0-
degrees.
-1
-0.5
0
0.5
1
1.5
2
2.5
3
-40
-20
0
20
40
60
80
100
Tilt
Of
fs
et
(De
gre
es
o
f Ti
lt)
Ambient Temperature (Degrees C)
Tilt Offset At 0-Degrees of Tilt
The tilt measurement is skewed when the temperature is significantly
above or below room temp.
