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IMU sensor basics | Inertial Measurement Unit

This page describes IMU sensor basics. The term IMU stands for Inertial Measurement Unit. IMU contains accelerometer, gyroscope and magnetometer.

What is IMU (Inertial Measurement Unit)?

• The single unit which houses an accelerometer and a gyroscope is known as IMU or Inertial Measurement Unit. It may also contain magnetometer.
• It provides necessary data to maneuver aircraft, spacecraft and watercraft especially when GPS signals are not available.

Let us understand sub units of IMU viz. accelerometer, gyroscope and magnetometer.
➨Accelerometer is a sensor which measures acceleration as well as gravity.
➨gyroscope measures rate of rotation of the device (i.e. angular velocity) in which it is mounted.
➨Magnetometer measures magnetic field surrounding to itself. This helps in determining its orientation relative to the magnetic field of the earth.

Accelerometer

MEMS Accelerometer

• Acceleration refers to rate at which velocity changes over time. Accelerometer is a sensor which measues acceleration as well as gravity. Its output is in units of gravity (i.e. letter 'g').
• It is used in the mobile phones to determine orientation of the phone with respect to ground. This helps to rotate the picture or screen display appropriately for user to view.
• Now-a-days accelerometer is packed along with gyroscope and magnetometer.
• The figure-1 depicts accelerometer implementation using MEMS.
accelerometer basics and working >> and advantages and disadvantages of accelerometer >>.

Gyroscope

MEMS gyroscope-A tilt sensor

• Definition: The device which is used for navigation and angular velocity measurement is known as Gyroscope. The Gyroscope made using MEMS technology is known as MEMS gyroscope.
• The MEMS gyroscope uses very small vibrating mechanism to detect changes in orientation. The gyroscopes can measure rotational velocity of one, two or three direction axis. 3-axis accelerometer is used to implement 3-axis gyroscope.
• There are various types of gyroscope viz. Mechanical Gyroscope, electronic gyroscope, MEMS gyroscope etc.
• The figure-2 depicts gyroscope implementation using MEMS.
➨Refer MEMS Gyroscope >> and difference between accelerometer and gyroscope >>.

Magnetometer

Earth Magnetometer

• Magnetometer is a device used to measure magnetic fields present around us. Magnetic fields are generated by current carrying conductor.
• The magnets creates magnetic field. Even our earth has its own magnetic field. Earth's magnetic field strength is proportional to 1/r3.
• Magnetometer is classified into various types viz. vector magnetometer, scalar magnetometer, Coil Magnetometer, Hall Effect Sensor Magnetometer, Magneto-resistive, Magneto-strictive, Fluxgate, Overhauser, Optically pumped Magnetometer etc.
• The figure-3 depicts Earth magnetometer.
➨Refer Magnetometer basics and types >> and advantages & disadvantages of magnetometer sensor >>.



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