28029 Parallax Inc, 28029 Datasheet - Page 251

• Manufacturer Part Number: 28029
• Description: KIT PARTS SMART SENSORS W/TEXT
• Manufacturer: Parallax Inc

Specifications of 28029

• Accessory Type: Parts Kit
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: BASIC Stamp® or Javelin Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 28029PAR

Chapter 6: Accelerometer Projects · Page 239
Figure 6-12: Position Graph Derived from Initial Position, Initial Velocity and Acceleration Data
The equation that calculates position in the G17 cell is:
=G16+(F16*0.03)+((0.5*E17*9.8/100)*(0.03^2))
G16 is the position after the previous sample, which is S
, the initial position. F16*0.03
0
1
2
t, initial velocity multiplied by time. (0.5*E17*9.8/100)*(0.03^2) is
is v
/
at
, where t
0
2
is again 0.03 seconds.
While this technique is pretty accurate over short periods of time, some error creeps into
each measurement from several sources. Rough surfaces and vibration will effect the
acceleration measurements. Also, while the equations assume the acceleration between
each measurement is constant, in many cases, the acceleration will change during the
time between each sample. In addition, each accelerometer measurement will tend to be
a few percent off because of the nature of the MX2125. The MX2125's datasheet
(available from Memsic's web site - www.memsic.com) explains these errors, the largest
of which are called zero offset and sensitivity errors. They will vary from one chip to the
next, and they are also influenced by temperature. Taking precision measurements with
the MX2125 involves an A/D converter, a floating point coprocessor, and data collected
from calibration tests. This calibration procedure is outside the scope of this text. To
find out more about this topic, consult #AN-00MX-002 Thermal Acceleromters
Temperature Compensation, which is available at Memsic's web site.