2.3.2 Power Saving Strategies
Write operations to the mircoSD card is the most significant power drain to the battery. Switching the
microSD card to SLC type memory will nearly double the operating time of the logger. Finding SLC
type microSD cards is very difficult since the flash memory industry has moved to MLC. However,
there are several feature configurations that will reduce power consumption and help extend the battery
life.
•
Use the deadBand feature to reduce the recorded data. Since the microSD card is the most
significant power draw, then reducing the data writes will translate into much better battery life.
For example, setting the deadBand=1024 will keep the logger from writing data to a file when
motion is less than 0.5g. Reducing the data by 20% can increase the battery life by 30%.
•
Turn off the over-sample/FIR filter feature using the “filterOff” option. This will reduce the
power consumption by about 20% at the expensive of lower effective resolution (see the
discussion in section 4.1.1)
2.4
Setting The RTC
A real time clock (RTC) integrated into the X16-5 determines the time for each line of data recorded.
The RTC is initialized using a user-created text file named “time.txt” that is loaded by the logger upon
booting. The time file method of setting the RTC does not require special communication drivers, so it
can be implemented using a simple text editor. Direct initialization of the RTC is possible but requires
specific device drivers and software from Gulf Coast Data Concepts.
Initializing the RTC with a time.txt file is accomplished as follows:
Step 1: Use Wordpad, or an equivalent text editor, to create a simple text file called
“time.txt”.
Step 2: Enter on the first line the current date and time as “yyyy-MM-dd HH:mm:ss” in
24-hr format. Figure 11 provides an example time.txt file that will initialize the
RTC to 2:26:30 pm June 16, 2014.
Step 3: Save this file to the root directory of the microSD card (same location as the
config.txt file) and close the text editor.
Step 4: Remove the logger form the PC. The logger will automatically find the time.txt
file and intialize the RTC with the time stored in the file. The file is deleted after
initialization.
The RTC maintains ±50ppm accuracy (-40°C to +85°C), which means that the accuracy may drift
about 4 seconds every day. The RTC is powered by the battery at all times, even when the logger is
“off”.
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X16-5, Rev New
The logger is always “on” maintaining the real time clock and will eventually discharge the
battery completely after several months. The completely discharged battery will take
additional time to recharge. Keep in a cool (20°C/ 68°F) dry environment to avoid damage
of the battery pack.
