Which device measures angular rate around three axes?

• A. 3-axis accelerometer
• B. 3-axis gyroscope
• C. Magnetometer
• D. Tilt sensor

Answer: (B)

Angular rate around three axes refers to how fast something is rotating about each of the x, y, and z axes. A gyroscope is the instrument that measures this rotation rate, and a 3-axis gyroscope provides three values, one for each axis, giving the full angular velocity vector. This is different from an accelerometer, which measures linear acceleration along each axis (including gravity) and does not capture rotation speed. A magnetometer measures magnetic field and is useful for heading estimation rather than rotation rate. A tilt sensor detects orientation relative to gravity but not how quickly the object is rotating. Therefore, the device that measures angular rate around all three axes is the 3-axis gyroscope.