Gulf Coast Data Concepts X16-1C User manual

USB Accelerometer
Model X16-1C
1 Features
•3-axis accelerometer
•Single gain mode set to +/-16g
•15-bit resolution
•User selectable sample rate of 12, 25,
50, 100, and 200 ertz
•User selectable deadband setting
•Accurate time stamped data using Real
Time Clock (RTC)
•Convenient on/off button
•Data recorded to a removable microSD
card (2GB included)
•Easily readable comma separated text
data files
•Data transfer compatible with Windows
or Linux via Universal Serial Bus
(USB) interface (no special software)
•System appears as USB Mass Storage
Device to Windows and Linux OS’s.
•Standard replaceable “AA” type battery
•LED indicator lights for system status
•Weighs 2oz (55g) with alkaline battery
2 Applications
The X16-1C is applicable to:
•Continuous time stamped shock and
motion monitoring of critical freight.
•Monitoring human motor activity, or
actigraphy, such as exercise intensity or
sleeping disorders.
•Automotive performance monitoring
•Educational purposes
3 Description
The USB Accelerometer X16-1C uses a low
noise digital accelerometer sensor, precise time
stamped data logging, microSD memory
storage, real-time data access and USB
connectivity. Acceleration is collected in X, Y,
and Z axes and stored at a user selectable rate
of up to 200hz. When connected via the USB
to a personal computer, the X16-1C appears as
a standard mass storage device containing the
comma delimited data files and user setup files.
The commercial standard “AA” battery
provides extended life operation suitable to
long term data acquisition applications.
Figure 1: USB Accelerometer X16-1C
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USB Accelerometer Model X16-1C
3.1 Operating Instructions
The X16-1C is a simple, economical solution to capture continuous motion data and quickly deliver
the information for analysis. The following instructions outline the steps to begin using the X16-1C.
Configuration settings and mounting methods will depend on the particular application.
Step 1: Disassemble the enclosure by unscrewing the #6 machine screw. Place a
AA type battery into the battery holder with the positive battery terminal
facing away from the USB connector. Reassemble the enclosure.
Step 2: Plug the X16-1C into a computer and allow the computer operating
system to register the device as a Mass Storage Device.
Step 3: Configure the X16-1C by editing the appropriate tags in the config.txt
file located in the root directory of the microSD card. Choose faster
sample rates to capture fast acceleration events. Setting the deadband
will filter small sensor readings, reduce the number of write operations to
the microSD card, and extend the battery life. Use the combination of
deadband and dwell to captured triggered events (see section 3.2.4.3).
Step 4: If necessary, initialize the RTC clock by creating a time.txt file (see
section 3.2.6).
Step 5: Unplug the X16-1C from the USB port and firmly attach the system to
the target object. Depending on the g-force intensity expected, tape, tie-
wraps, pipe clamps, or glue are suitable methods of attachment. The
0.75” #6-32 screw can be replaced with a longer screw to firmly attach
the X16-1C enclosure to the target object.
Step 6: Press the button located at the rear of the enclosure to initiate data
recording, (see Figure 2). The red LED will blink as the configuration
file is accessed. If the time.txt file is present, the RTC is initialized with
the time written in the file. Then, the blue LED will begin to blink at a 1
second interval indicating the system is operating. The red LED will
blink periodically as data is written to the microSD card.
Step 7: To stop recording, press and hold the on/off button for about 3 seconds.
The LEDs will begin to blink rapidly for 2 seconds. Release the button
and the X16-1C turns off. Data recording is restarted by pressing the
button again (see Step 5).
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USB Accelerometer Model X16-1C
Figure 2: Starting t e X16-1C
3.2 Electrical
3.2.1 Sensor
Table 1: Accelerometer Sensor C aracteristics
Parameter Condition Min Typical Max Units
Acceleration range ±16.0 g
Resolution 0.001 g/count
Linearity X, Y, Z axis ±1 %FS
Zero-g Offset Level
Accuracy
X, Y axis -150 +150 mg
Z axis -250 +250 mg
Inter-Axis Alignment Error ±0.1 Degrees
Cross-Axis Sensitivity ±1 %
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USB Accelerometer Model X16-1C
Figure 3: Accelerometer Sensor Orientation
3.2.2 Indicator LEDs
System status is indicated by the two LEDs located near the USB connector. The blue LED indicates
system operation. A steady blinking blue LED, once per second, indicates a properly operating
system. The blue LED blinks once per second when the USB Accelerometer is recording data, in
standby mode, or is connected to a computer via the USB port. The red LED blinks when data is
written from the internal cache to the microSD memory card. The period at which the red LED blinks
depends on the deadband setting and sample rate. The red LED will also blink with uman Interface
Device ( ID) communication activity when connected to a PC. The “statusindicators” tag in the
configuration file turns off or changes the brightness of the status indicators (see section 3.2.4.11).
3.2.3 Battery
3 2 3 1 Main Battery
The X16-1C is powered by a single “AA” sized battery. Typical operation times using an alkaline
battery range from 3 to 7 days depending on system configuration, battery quality, and microSD card
type. The RTC continues to operate from the battery when the device is “off”. The RTC should be
reinitialized if the battery is removed or depleted. The battery is not used when the device is connected
to a computer USB port.
Gulf Coast Data Concepts recommends an alkaline battery (ANSI type 15A or IEC type LR6) or
lithium battery (ANSI type 15L or IEC FR6) to operate the X16-1C. A lithium (Li/FeS2) battery
provides approximately 30% more capacity and wider operating temperature range than an alkaline
battery. Extended operation is achieved by connecting a 5V supply via the USB connector (such as a
personal electronics USB charger or USB battery pack).
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USB Accelerometer Model X16-1C
3.2.4 System Configuration Options
The X16-1C is configured using a set of tags and settings stored in a text file named “config.txt”,
which is located in the root directory of the microSD card. The system reads the configuration file at
boot time. Table 2 lists the configuration file tags. A tag is followed by an equal sign (“=”) and an
applicable tag setting. A line finishes with a newline character (For Windows systems, Wordpad is
recommended for editing the config.txt file. Notepad does not terminate lines appropriately). Tags are
not case sensitive. Tab and space characters are ignored. Lines starting with a semicolon (“;”) are
treated as comments and ignored by the system. The system will use the default settings listed in
Table 2 if the config.txt file is not found.
Table 2: Configuration File Tags and Descriptions
Tag Valid Settings Default Description
deadband An integer between
0 and 32767
0 Sets the deadband to a range expressed in “counts”.
A new sample is recorded if any sensor axis
exceeds the previous recorded reading by the
deadband value
deadbandtimeout An integer between
0 and 65535
3 Specifies the period in seconds when a sample is
recorded regardless of the deadband setting. This
feature ensures periodic data is recorded during
very long periods of inactivity.
dwell An integer between
0 and 65535
1 The number of samples recorded after a deadband
threshold triggered event
microres - Off The presence of this tag sets the device to record
time stamps with 0.1ms effective precision.
rebootondisconnect - off on disconnect The presence of this tag causes the system to start
recording after disconnect from a USB port.
rtcclocktrim An integer between
-127 and 128
0 Fine adjustment for RTC correction
samplesperfile An integer greater
than 0
28896 The number of lines of data per data file before a
new file is created
samplerate 12, 25, 50, 100, 200 25 Sets the rate at which data is collected and recorded
to the microSD card.
starttime and stoptime See section 3.2.4.9 - Defines when to start and stop recording
stoponvusb - Off Stops data logging if 5v USB power is present (see
section 3.2.4.10)
statusindicators “Normal”, “ igh”,
“Off”
Normal LED status indicators can be activated with normal
brightness (Normal), activated with high brightness
( igh), or completely deactivated (Off).
timeoutonusb - Off Stops USB if no host communications detected (see
section 3.2.4.12)
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USB Accelerometer Model X16-1C
3 2 4 1 deadband
“deadband” defines the minimum difference between recorded sensor readings. A new sample from
the accelerometer sensor must exceed the previous recorded reading before the microcontroller records
the data. The deadband setting is expressed in "counts" units and is applied to the output of each axis.
There are 1024 counts per g. The deadband value can be set to an integer between 0 and 32767. The
deadband function is an effective way to reduce the amount of data collected and extend the system
battery life. The deadband functions as a event threshold limit when used in conjunction with the
“dwell” feature.
Figure 4: Grap ical Illustration of t e Deadband Feature
3 2 4 2 deadbandtimeout
“deadbandtimeout” defines the period in seconds when a sample is recorded by the device regardless
of the deadband setting. This feature ensures periodic data is recorded during extended periods of
inactivity. A valid setting for the deadbandtimeout is an integer between 0 and 65535.
3 2 4 3 dwell
The “dwell” tag defines the number of consecutive samples recorded at the set sample rate after a
deadband threshold event. The deadband threshold event occurs when a sensor reading exceeds the
last recorded value by the deadband setting. A valid dwell setting is an integer between 0 and 65535.
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USB Accelerometer Model X16-1C
Figure 5: Grap ical Illustration of t e Dwell Feature
3 2 4 4 microres
The “microres” option sets the device to record time stamps with 0.1ms precision. In micro-resolution
mode, the time stamps are recorded as XX.YYYYZZ where XX are seconds, YYYY are 0.1
milliseconds, and ZZ are spurious digits that should be ignored. The micro-resolution option should be
implemented at sample rates of 100 hertz or greater to provide the best timing precision. The power
saving features of the X16-1C are disabled in micro-resolution mode and battery life is shortened
accordingly.
3 2 4 5 rebootondisconnect
The X16-1C incorporates an on/off button for initiating and terminating the data recording process.
Data recording is automatically started upon disconnect from a computer USB port if the tag word
“rebootondisconnect” is included in the configuration file. Note that the system must first be turned on
and the configuration file read before the rebootondisconnect option is implemented by the system.
Subsequent disconnects will then cause a reboot and immediate data recording.
3 2 4 6 rtcclocktrim
The “rtcclcocktrim” setting adjusts the RTC oscillator frequency. Positive values increase the
oscillation period (lower frequency) and negative values decrease the oscillation period (higher
frequency). A valid setting is an integer between -127 and 128. By default, the RTC provides +/-
2ppm (parts per million) precision between 0°C and 40°C. This feature should be used by advanced
users only.
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USB Accelerometer Model X16-1C
3 2 4 7 samplesperfile
“samplesperfile” defines the number of data lines each file can have before a new file is created. This
tag controls the size of the data files into easily manageable lengths for later processing. This setting is
loaded as a signed 32-bit integer, which can translate into very large data files. The user should
exercise caution before setting large files and test the end-user application for data limitations.
3 2 4 8 samplerate
The “samplerate” tag defines the data rate in ertz, or samples per second. Valid sample rate settings
are 12, 25, 50, 100, and 200 z. At 100 z or greater, the configuration file should also include the
“microres” tag to provide the best timing precision (see section 3.2.4.4).
3 2 4 9 starttime and stoptime
The X16-1C starts and stops data recording based on the times defined using the “starttime” and
“stoptime” tags. The times must be in “DD MM ” 24-hr format with the three entries separated by
a space. Entries marked with “*” operate as a wild card. The X16-1C continues to record after the
start time unless defined otherwise by the stoptime tag. Note that the configuration option does not
include the month. Example timing configurations:
Example 1: On the 15th day, start recording at 12:30pm and stop
recording at 6:00pm.
starttime = 30 12 15
stoptime = 00 18 15
Example 2: Start recording at the beginning of every hour and stop
recording 45 minutes later.
starttime = 00 *
stoptime = 45 *
3 2 4 10 stoponvusb
The “stoponvusb” tag stops data logging operations when a 5v supply is detected on the USB
connector. By default, the device switches power from the internal battery to the USB 5v and
continues to log data.
3 2 4 11 statusindicators
The brightness intensity of the LED status indicators is defined using the “statusindicators” tag and
valid settings of “normal”, “high”, and “off”.
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USB Accelerometer Model X16-1C
3 2 4 12 timeoutonusb
The “timeoutonusb” tag returns the microprocessor to normal operating speed if no USB
communications are detected within 7 seconds after connection to a USB port. This reduces the power
requirements when operated from an external 5v USB supply. By default, the microprocessor
continues at high-speed mode waiting for USB communications. Utilize the timeoutonusb feature
when operating the device from an external 5v USB battery pack.
3 2 4 13 Example Configuration Files
Example A) The following configuration records data constantly at 25 hertz. The device will boot and
begin logging data once removed from a computer USB port. Each data file is 30,000 lines long or
about 25 minutes.
Figure 6: Configuration File Example A
Example B) Setting the deadband to 50 counts causes the device to record only changes greater than
0.05g. The deadbandtimeout setting forces a sample write every 60 seconds. Status indicators will
turn off about 10 seconds after the device turns on.
Figure 7: Configuration File Example B
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USB Accelerometer Model X16-1C
Example C) The micro-resolution is activated to provide the best timing precision at the 100 z
sample rate. If motion exceeds 100 counts (0.1g), the device captures continuous data 100 times a
second for 2 seconds or until the change in acceleration falls below 0.1g. The timeoutonusb option
reduces the system power requirements while connected an external 5v USB battery pack.
Figure 8: Configuration File Example C
3.2.5 Data Files
Data is written to files in comma separated text format starting with the file header information and
followed by event data entries. Each data line contains a time entry and the raw accelerometer sensor
readings from the X, Y, and Z axes. The time entry is in seconds past the start time recorded in the
header. The raw sensor data format is signed digital “counts”. The raw counts are converted to “g” by
dividing the value by 1024. Table 3 lists the valid header tags, although not all tags may occur in the
header.
The X16-1C creates a new data file when the system is booted or when the maximum number of data
lines is reached in the previous data file. A system boot condition occurs when the on/off button is
pressed, 5v power is restored to the system via the USB connector, or when the X16-1C is removed
from a computer USB port with the “rebootondisconnect” feature enabled. Data files are placed in a
folder named “GCDC” and are named data-XXX.csv, where XXX is a sequential number starting with
001. The system will create up to 999 files. At the beginning of each file, a header is written
describing the system configuration and the current time when the file was created. Figure 9
represents an example data file.
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USB Accelerometer Model X16-1C
Table 3: Data File Header Tags
Tag Description
DEADBAND A new sample from the sensor must exceed the last reading by the
deadband value
DEADBANDTIMEOUT The period in seconds when a sample is recorded regardless of the
deadband setting
GAIN Always indicates “low” for the X16-1C
EADERS The names of each column of data in the file
SAMPLERATE Rate at which data is recorded to the microSD card
START_TIME The current time when the data file was created
TEMPERATURE Temperature of sensor in °C when data file was created
TITLE The name of the USB Accelerometer X16-1C unit
VERSION The version control information of the USB Accelerometer firmware
Figure 9: Example Data File
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USB Accelerometer Model X16-1C
3.2.6 Real Time Clock
A real time clock (RTC) is integrated into the X16-1C system and is used to determine time for each
line of data recorded. The RTC maintains ±2ppm accuracy (0°C to +40°C) and is powered by the
primary battery. The RTC will reset if the battery is removed or depleted. The RTC also provides the
system temperature (°C) recorded to the header of each data file.
The RTC is set using a text file named “time.txt” located in the root directory of the microSD card.
The system looks for the time.txt file upon booting. If the file exists, the time stored in the file is
loaded to the RTC and the time.txt file is deleted. The time information in the time.txt file must be in
the exact “yyyy-MM-dd :mm:ss” 24-hour format, occur on the first line, and end with a newline
character. The time file method of setting the RTC does not require special communication drivers so
it can be implemented using any text editor. Direct initialization of the RTC is possible but requires
specific device drivers from Gulf Coast Data Concepts.
3.2.7 Memory Card
The X16-1C stores data to a removable 2GB microSD flash memory card. The device operates using
FAT16 file structure, which limits the maximum microSD card capacity to 2GB. The “config.txt” and
“time.txt” files must occur in the root directory (see section 3.2.4 and section 3.2.6). The X16-1C
functions as a Mass Storage Device to computer operating systems when transferring data to and from
the microSD memory card.
The X16-1C is compatible with microSD and microSD C type cards but the card must be formatted to
FAT16 for proper operation of the X16-1C. Under Windows XP, the card must be formatted using the
“FAT” file system and the default allocation size. Do not select “Quick Format” or “FAT32”. The
X16-1C will create a folder called “GCDC”, if not already present, to place the data files (see section
3.2.5).
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USB Accelerometer Model X16-1C
3.3 Mechanical
The X16-1C electronics are enclosed in a three-part plastic enclosure. The semi-transparent blue
colored ABS plastic allows attenuated sight of the two indicator LEDs. The top and bottom enclosure
components and the printed circuit board are secured together with a 0.75” long #6-32 screw and nut.
Longer screw lengths can facilitate attachment of the X16-1C to other structures. A slip-on cap
protects the USB connector. The X16-1C weighs 2oz (55g) with an alkaline battery.
3.3.1 Dimensions
Figure 10: Enclosure Dimensions
3.3.2 Assembly
Figure 11: Exploded View of USB Accelerometer X16-1C
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1.01
1.04
4.10
0.75" Length
#6-32 Machine Screw
PCB Encl sure
(T p)
PCB Encl sure
(Cap)
Printed Circuit B ard
PCB Encl sure
(B tt m)
#6-32 Hex Nut

USB Accelerometer Model X16-1C
4 Software
The X16-1C records data to comma delimited text files and uses text based files for configuration
settings. Therefore, no special software is required to utilize the X16-1C. owever, Gulf Coast Data
Concepts provides the Java based software program XLR8R that allows easy visual presentation of the
data, copy-paste export of data segments, as well as configuration file and time file creation utilities.
XLR8R is included on the microSD card of each X16-1C unit or can be downloaded from the website
at www.gcdataconcepts.com. For data analysis, Gulf Coast Data Concepts recommends using a
commercial or open source mathematics package, such as MatLab, Microsoft Excel, OpenOffice Calc,
Octave, R, or similar applications.
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