http://www.analog.com/UploadedFiles/...ADXL202E_a.pdf
Duty Cycle Decoding
The ADXL202E’s digital output is a duty cycle modulator.
Acceleration is proportional to the ratio T1/T2. The nominal
output of the ADXL202E is:
0 g = 50% Duty Cycle
Scale factor is 12.5% Duty Cycle Change per g
These nominal values are affected by the initial tolerance of the
device including zero g offset error and sensitivity error.