User Manual
Slam Stick User Manual
Version No. 2.0
29
NOTE:
Although the device can use temperature or pressure to start a recording, it will
not stop the recording if the temperature/pressure returns to a level inside the trigger
range. Limit the recording length and turn on re-triggerable if you are only interested in
data when it is outside the specific temperature and/or pressure range
Acceleration Trigger (Analog)
The acceleration trigger should be used when the application asks that only vibrations exceeding
a specific acceleration should be measured. This is a useful trigger for measuring shock events,
and when coupled with the Limit recording time to trigger, the battery life can be extended for a
Slam Stick and save the user from obtaining unwanted data.
The Slam Stick X piezoelectric accelerometer has a DC offset that is removed in the Slam Stick
Lab. But the device does not account for this level and calibration of the DC offset proved
impossible because of its dependence on temperature change rate. Therefore if using an Analog
acceleration trigger it is best to use a level greater than 1/5 the measurement range. For
example, a 25g accelerometer should not have a trigger level less than 5g. If you would like to
trigger off smaller levels it’s strongly encouraged to use the DC accelerometer as the trigger. Note
that this is not a concern for Slam Stick S (uses a piezoresistive accelerometer) customers.
But if the user would prefer to use the piezoelectric accelerometer as the trigger you will need
to determine the offset values of an accelerometer, do the following:
1.
Set the Slam Stick on a flat surface and take a recording. Do not apply an external vibration
to the Slam Stick.
2.
After 10 seconds, stop the recording and open the data file in the Slam Stick Lab software
(see the ‘Analysis’ section for information on how to view data in the Slam Stick Lab
software)
3.
Select “Data” (at the top of the viewing window)
4.
Select “Remove Mean” and then “Do Not Remove Rolling Mean”
5.
Observe the ‘g’ value that each axis corresponds to in the data. Those are the baseline
values that should be used when setting an Acceleration trigger. Depending on the
orientation of the device, the offset may or may not differ.
NOTE:
The offset values should be used as a baseline for setting the Acceleration trigger
values and it is suggested that the Acceleration trigger value be set to no less than 0.5g
away from the offset value.
Acceleration Trigger (DC)
This trigger uses the DC MEMS accelerometer for triggering. Midé highly recommends using this
trigger over the analog accelerometer trigger for three reasons. One, there is no concern over
the moving DC offset for this accelerometer. Two, this accelerometer is much lower power so it
will last longer in this trigger mode. The third reason is that you can trigger for a specific axis.
