Versatile Bio Sensor Guide: IMU

Understanding the inertial measurement unit sensor on the Versatile Bio


What it measures:

The inertial measurement unit (IMU) measures the linear and angular acceleration and orientation relative to the earth's magnetic field.  The IMU combines a gyroscope, accelerometer and magnetometer (compass), each operating in 3 axes of space for measurement of 9 degrees of freedom.


The sensor measures the movement and position of whatever it is attached to.  Up to 16 different IMU sensors can be connected to the Versatile Bio via the optional multiplexer upgrade.

Research Applications:

Biomechanics, Kinesiology,  sports, professional performance, etc.  IMU can also be used as a method of artifact removal and error correction when using other sensors (GSR, EEG, EMG, etc). 

How to use:

The IMU sensor is placed on the part of the participant to be tracked (i.e. the head, hand, etc). 

The magnetometer can be adversely effected by competing magnetic fields or EMF interference. 

Connector on Versatile Bio:

Digital Auxiliary Input

Visualization filters:

A data visualization filter is not necessary for IMU.  You may have to reduce the data scale until you see a signal. 

Data file:


The IMU system reports the following:

  • Channel 1:  X Axis, Linear Acceleration
  • Channel 2:  Y Axis, Linear Acceleration
  • Channel 3:  Z Axis, Linear Acceleration
  • Channel 4:  X Axis, Angular Acceleration
  • Channel 5:  Y Axis, Angular Acceleration
  • Channel 6:  Z Axis, Angular Acceleration
  • Channel 7:  X Axis, Magnetic Orientation
  • Channel 8:  Y Axis, Magnetic Orientation
  • Channel 9:  -Z Axis, Magnetic Orientation


Scales and Sensitivities of the individual sensors in the IMU:

  Sensor Scale Sensitivity
Linear Acceleration Accelerometer ±8g 0.24 mg
Angular Acceleration Gyroscope ±1000 º/s 0.03 º/s
Orientation Magnetometer ±4200 µT 0.6 µT

 

Data Conversion:

(VALUE) = recorded value in data file

  Sensor Conversion
Linear Acceleration (X, Y, Z) Accelerometer Acc in G = (VALUE) / 4096
Angular Acceleration (X, Y, Z) Gyroscope Acc in deg/second = (VALUE) / 32.8
Orientation (X, Y, Z) Magnetometer Mag in µT = (VALUE) * 0.6

 

Sensor Axis orientation

  • X, Y and Z are coaxial for the accelerometer and gyroscope
  • Z orientation is reversed for the magnetometer
  • Diagram for axis orientation for accelerometer and gyroscope:
  • Diagram for axis orientation for magnetometer:



Digital Multiplexer


This is an optional add-on that allows the connection of up to 8 IMU sensors per digital AUX input channel, for a total of 16 possible IMU sensors via two multiplexers.  See Versatile Bio Sensor Guide: IMU Multiplexer for more details.