Theory of Operation

BEI GyroChip
(aka the Quartz Rate Sensor (QRS) )

The GyroChip uses a vibrating quartz tuning fork 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's 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 "Coriolis Acceleration," 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.