MEMS gyroscope

A gyroscope measures rotation — how fast you are turning — and the MEMS version has no spinning wheel at all; instead it relies on a ghostly force called the Coriolis effect. Imagine walking straight toward the centre of a spinning merry-go-round: to anyone on the ride you appear to veer sideways, pushed by an invisible force. A MEMS gyro builds a tiny tuning fork or ring that is kept constantly vibrating back and forth; when the whole chip rotates, that vibration gets nudged sideways by exactly this Coriolis push, and the sideways nudge is proportional to how fast the chip is turning. Sense that sideways motion (again as a capacitance change) and you have measured angular rate.

The output is degrees per second (°/s), not an angle — so to know your heading you must integrate the rate over time, which means a small constant error ("bias") slowly piles up into a growing angle error called drift. A cheap phone gyro might drift several degrees per minute; a navigation-grade unit, far less. This is why a gyro is almost never used alone: it gives fast, smooth short-term rotation but wanders over minutes, while an accelerometer gives a noisy but absolutely-referenced 'down' direction. A sensor-fusion filter blends them so the gyro handles quick motion and the accelerometer quietly corrects the long-term drift — the partnership inside every drone, phone, and VR headset.