Gyroscope Primer

Introduction

A MEMS (microelectrical-mechanical system) gyroscope is a device that is used for measuring orientation. Accelerometers can perform a similar function when they are stationary by measuring the components on each axis of Earth's gravitational field. However, if the accelerometer is experiencing acceleration other than gravity it will not be able to distinguish and consequently will not be able to determine orientation. This is where gyroscopes become useful.

How Gyroscopes Work

Gyroscopes contain small strips of metal that bend when the gyro twists and moves. By measuring the amount of bending the gryo can accurately report what angular velocity it is experiencing. Angular position is often what is desired however. In order to obtain angular position the angular velocity can be integrated over time. Once integrated the data will be similar to the data from a 3 axis compass, it is important to note however that the gyro data will be with respect to an arbitrary 0 where as the compass is with respect to the Earth's magnetic field. This means that the gyroscope will more often than not give you different numbers than the compass. The only time this is not true is when the gyro is zeroed directly parallel with the Earth's surface and pointing to the North magnetic pole.

Basic Use

In general gryoscopes must be calibrated, most are calibrated at the factory where they are manufactured though. Check the data sheets for the gyro you have to see if it requires manual calibration.

Once calibrated you are ready to start using the gyro. When you power it up you need to hold it as still as possible and then use the zero function or button to make the gyro ready to take accurate measurements.

Note that the gyro headings are the roll, pitch and yaw of the gyro with respect to the arbitrary zero point set at the beginning.