An Introduction to Quartz Inertial Technology
Systron Donner Inertial's family of
quartz inertial sensors use one piece, micromachined inertial sensing
element to measure
angular rotational velocity. These sensors produce a signal output proportional to the
rate of rotation sensed.
SDI’s unique quartz inertial sensors
are micromachined using photolithographic processes, and are at the forefront of MEMS
(Micro Electro-Mechanical Systems) technology. These processes are similar to those used
to produce millions of digital quartz wristwatches each year. The use of piezoelectric
quartz material simplifies the sensing element, resulting in exceptional stability over
temperature and time, and increased reliability and durability.
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BEI GyroChip®
The GyroChip® uses vibrating quartz tuning tines to sense rate, acting as a Coriolis sensor, coupled to a similar fork as a pickup to
produce the rate output signal.
Each comprised of a pair of tuning forks, the GyroChip along with their support flexures and frames are batch fabricated from thin
wafers of single-crystal piezoelectric
quartz.
The piezoelectric drive tines are
driven by an oscillator to vibrate at a precise amplitude, causing the tines to move
toward and away from one another at a high frequency. This vibration causes the drive fork
to become sensitive to angular rate about an axis parallel to its tines, defining the true
input axis of the sensor.
Vibration of the drive tines causes them to
act like the arms of a spinning ice skater, where moving them in causes the skater's spin
rate to increase, and moving them out causes a decrease in rate. For vibrating
tines ("arms"), an applied rotation rate causes a sine wave of torque to be
produced, resulting from the oscillating torque at frequency of the drive
tines, in turn causing the tines of
the pickup fork to move up and down (not toward and away from one another) out of the
plane of the fork assembly.
The pickup tines thus respond to the
oscillating torque by moving in and out of plane, causing electrical output signals to be
produced by the Pickup Amplifier. Those signals are amplified and converted into a DC
signal proportional to rate by use of a synchronous switch (demodulator) which responds
only to the desired rate signals.
The DC output signal of the GyroChip is
directly proportional to input rate, reversing sign as the input rate reverses, since the
oscillating torque produced by Coriolis reverses phase when the input rate reverses.
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