6
5.1 ActiveThreshold and InActiveThreshold
Formula
Active Threshold/
InActiveThreshold =
Critical value ÷ 9.8
÷ 0.0625
* The gravitational acceleration at standard atmospheric pressure is 9.8 m/s
2
* The scale factor of the threshold is 62.5 mg
Active Threshold
Active Threshold can be changed by ConfigureCmd
Active Threshold range is
0x0003-0x00FF
(default is 0x0003);
InActiveThreshold
InActiveThreshold can be changed by ConfigureCmd
InActiveThreshold range is
0x0002-0x00FF
(default is 0x0002)
* Active Threshold and
InActiveThreshold can not be the same
Example
Assuming that the critical value is set to be 10m/s
2
, the Active Threshold would be set
10/9.8/0.0625=16.32
Active Threshold would be set integer as 16.
5.2 Calibration
The accelerometer is a mechanical structure that contains components that can move freely.
These moving parts are very sensitive to mechanical stress, far beyond solid-state electronics.
The 0g offset is an important accelerometer indicator because it defines the baseline used to measure acceleration.
After installing R311FD, users need to let the device rest for 1 minute, and then power on. Then, turn on the device and wait for
the device taking 1 minute to join the network. After that, the device will automatically executes the calibration.
After calibration, the reported three-axis acceleration value will be within 1m/s
2
.
When the acceleration is within 1m/s
2
and the
velocity is within 160mm/s, it can be judged that the device is stationary.
