ADXl278: Linearity measurement and drift

Document created by analog-archivist Employee on Feb 23, 2016
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We are interested in using the ADXL278, split range 37/70g sensor for inertial
and shock measurement during an impact test. I have reviewed the specification
and have a few questions: 1, How do you derive the linearity measurement of
0.2% to 2%? 2, Do the sensors suffer from any drift or hysteris, thermal,
mechanical etc.

 

1. How do you derive the linearity measurement of 0.2% to 2%?
The linearity of the devices is measured on all devices in production. It is
based on a direct relationship between THD and non-linearity. We measure THD
and can directly calculate the maximum non-linearity from this measurement and
mathematical relationships between THD and non-linearity.

2, Do the sensors suffer from any drift or hysteris, thermal, mechanical etc.
All mechanical sensors exhibit temperature drift and hysteresis. Our devices
are measured for performance at both the hot and cold ends of the rated
temperature range. All min's and max's on our datasheet are fully measured and
guaranteed in production. Our mechanical designs do not require temperature
compensation, so there are no step discontinuities when sweeping the devices
over temperature (such as with digital temperature compensation.)

As for mechanical hysteresis, our devices do not perform differently on the
return from impulse than on the impulse - they move only a very small distance
of the total available gap when an input acceleration is applied, as their
resonant frequency (directly related to the spring constant of the structure)
is quite high (24kHz).

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