Application

# What Is The Functional Difference Between A Gyroscope And An Accelerometer?

An accelerometer is used to measure acceleration.A triaxial accelerometer can measure the direction of movement of a stationary platform relative to the Earth’s surface, but once the platform is in motion, things get much more complicated.If the platform is in free fall, the acceleration measured by the accelerometer is zero.If the platform accelerates in a certain direction, each axial acceleration value will contain the acceleration value generated by gravity, which makes it impossible to obtain the real acceleration value.For example, a triaxial accelerometer mounted on an aircraft with a roll Angle of 60 degrees would measure a vertical acceleration of 2G, when in fact the plane’s relative surface is tilted at 60 degrees.Therefore, the use of accelerometers alone cannot keep an aircraft on a fixed course.

The gyroscope measures the angular rate of rotation of the body around an axis.When the gyroscope is used to measure the angular rate of rotation in the axial direction of the aircraft body, the measured value is non-zero if the aircraft is rotating, and zero when the aircraft is not rotating.Thus, the gyroscope on an aircraft with a roll Angle of 60 degrees will measure zero roll angular rate, as will the gyroscope when the aircraft is flying straight and level.The current roll Angle can be estimated by the time integral of the angular rate value, provided that there is no accumulation of errors.Gyroscope measurements drift over time, and over the course of a few minutes or even seconds additional errors are bound to accumulate, ultimately leading to a completely incorrect understanding of the plane’s current roll Angle relative to the horizontal plane.Therefore, gyroscopes alone cannot keep an aircraft on a specific heading.

In a word, the accelerometer is correct over a long period of time (to determine the plane’s direction), and has errors over a short period of time due to the presence of signal noise.The gyroscope is more accurate in a short period of time and there will be error and drift in a long time.So you need both to make sure you’re on the right course.