ADXL202EB232 Analog Devices Inc, ADXL202EB232 Datasheet - Page 3

• Manufacturer Part Number: ADXL202EB232
• Manufacturer: Analog Devices Inc

Specifications of ADXL202EB232

• Lead Free Status / Rohs Status: Not Compliant

GRAPHS.
Click on one of the following icons; Line/Chart,
FFT, or Spirit Level to display the corresponding
graph.
Line Chart
The Line chart will show you the output of the X and
Y accelerometers in either % duty cycle or
acceleration in G’s. Using the drop down edit box
can change the amount of data that appears on the
graph. The amount of averaging can be changed
with the slide bar. The graph can be paused using
the pause/resume button on the lower right hand side
of the dialog box. The accelerometer can be zeroed
by pressing the zero button. This allows relative
measures to be performed.
FFT
The displayed parameter can either be the X or Y
acceleration in G.’s. The top trace is in the time
domain and the bottom graph is the frequency
response. The number of points to perform the FFT
on can be selected on the left side of the dialog box.
Spirit Level
The demo board can also be used as a tilt sensor that
this display demonstrates. The Roll axis is defined
to be the Ax axis and the Pitch axis is the Ay axis.
Holding the left mouse button while over the knob
will set the display range or by clicking on the
number and entering a value. For best results the
demo board should be calibrated prior to use.
CALIBRATION
Clicking on “Configure a Connection” allows the
user to modify the sensitivity and/or the 0-g value.
To automatically calibrate the sensitivity and the 0-g
value click on the “Calibrate” button. The software
calculates the sensitivity by the formula (Maximum -
Minimum)/2 where the Maximum and Minimum are
the maximum and minimum values seen per axis as
the demo board is rotated around. The 0-g value is
calculated by taking the average value of the
Maximum and Minimum values seen, (Maximum +
Minimum)/2. Care should be taken in rotating the
demo board in a smooth fashion. For best results the
demo board should be calibrated before each use.
Sampling Rate
The sampling rate is the rate of which the demo
board is sending data. To set the sampling rate click
on “Configure a connection”. One can either set the
maximum sample rate or a fixed sample rate. The
fixed sample rate must be at a rate the host computer
can sustain. To get the highest sampling rate, make
sure that the X-Analyze software is the only program
running and all other unnecessary programs has
been closed.
Analyze software and the Windows O.S. fixed rate
sampling can typically only be done at less than 60%
of maximum sample rate if the Update Rate is set to
“as fast as possible.”
Data Logging
To save the values to a file click on the “Log all
Connections” button. To stop data logging click on
“Stop Logging” button. Note the button will toggle
between “Log all connections” and “Stop Logging”
depending if data logging is active or not. Open the
Configure a connection window to specify the file
name, location and logging rate.
sampling is required, the best approach would be to
save the samples to a file and then perform post
processing. Also close any unused programs and
eliminate any screen or mouse activity. To get the
best constant rate, set the datalogging rate and the
update rate to the same value. Note: On occasion,
missing samples might be noticed, this is a
limitation in the X-Analyze software and Windows
O.S. There has been much work to reduce, but not
completely eliminate the problem.
Averaging
Software averaging improves the noise rejection,
however it reduces how quickly the accelerometer
can respond to changes. Adjust the setting to the
application requirements. The default setting is 5
averages.
COMMUNICATIONS PROTOCOLS
The default RS-232 parameters are 38400 baud, 8
data bits, 1 start bit, no stop bits.
protocol consists of a single ASCII command ‘G’
which returns a 4 byte data packet. The data packet
consists of 2 bytes each of X-axis and Y-axis duty
cycle data. See Tables 1,2, and 3.
Table 1: Data Commands
ASCII Decimal/(Hex)
G
Table 2: Packet Structure
Byte Number
1
2
3
71/(0x47)
Because of limitations in the X-
Value
0-255
0-255
0-255
Description
X Axis MSB
X Axis LSB
Y Axis MSB
Description
Request data
The RS-232
If constant