4.1.1 Sensor Special Features
The X16-5 implements an 8X over-sample and finite impulse response (FIR) filter algorithm at sample
rates up to 400Hz. This means that the digital accelerometer sensor provides 8X the sample rate
requested in the config.txt file. For example, “samplerate=400” sets the sensor to stream at 3200 Hz,
which is the maximum capability of the ADXL345. The eight samples are averaged and processed
through the FIR filter to improve the response characteristics. The oversampling and FIR algorithm
increases the sensor's native 13-bit resolution to the 16-bit data recorded in the data file.
The X16-5 will support sample rates of 800, 1600, and 3200 Hz but the X16-5 deactivates the
oversampling and FIR filter and records the native 13-bit resolution from the sensor. However, these
sample rates are not guaranteed and the time stamps may become inaccurate or the logger operation
could become unstable. Performance is dependent on the microSD card capability.
Figure 20 shows an example configuration setting the logger to record at 800 Hz. The 13-bit data from
the sensor is right padded (LSB) into a 16-bit value to maintain consistency with the oversampled data.
Therefore, the conversion factor is still 2048 counts/g.
4.2
Operating and Storage Conditions
The X16-5 is protected from general handling conditions by the plastic enclosure but is not protected
from adverse environmental conditions, such as rain, sweat, splashes, and water submersion. The
temperature range is limited primarily by the lithium-polymer battery capabilities, which begins to
degrade at about 40°F (4°C).
Gulf Coast Data Concepts
Page 20
X16-5, Rev New
Figure 20: 800Hz Sample Configuration
; Example X16-5 Config file
; set to 800Hz
samplerate = 800
; record constantly
deadband = 0
deadbandtimeout = 0
; set file length
samplesperfile = 100000
; set status indicators
statusindicators = normal
Add “filteroff” to the config.txt file to remove the over-sample/FIR filter algorithm and the
logger will record the native 13-bit resolution from the ADXL345 accelerometer sensor.
The recorded data is “right padded” to a 16-bit value so the conversion factor remains
2048 counts/g. The resulting data is less sensitive and noisier than the filtered data but
this option allows the end-user to implement custom filter algorithms post-process.
