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Motus Bioengineering Inc.


Sensor Comparison


Gyroscope - The best approach

  • Measures rotational motion -- human motion is rotational about joints.
  • Not influenced by gravity.
  • Both frequency & magnitude information accurate down to DC (zero frequency).
  • Only a single integration is needed to obtain angular displacement.
  • High signal to noise ratio.
  • High dynamic range.
  • Solid state gyros (with no spinning wheels) do not influence motion of subject being measured.
  • No intimate electrical contact with subject.
     
     
Accelerometer - inferior to Gyroscope (more info- click here)
  • Measures linear motion & gravity concurrently. Results cannot be decoupled without gyros. Does not measure human rotational motion.
  • Signal magnitude corrupted by gravity.
  • Frequency data good but bandwidth often not down to DC.
  • Difficult second integration required to obtain displacement.
  • Low signal to noise ratio piezoelectric accels. High for servo accels but includes gravity component.
  • High dynamic range.
  • Piezoelectric accels can be very small with no influence; servo accels much larger.
  • No intimate electrical contact with subject.

 

Electromyogram (EMG) - inferior to Gyroscope
  • Measures electrical current associated with muscular action. Does not measure movement directly.
  • Not influenced by gravity.
  • Frequency information good but magnitude less repeatable.  Contact resistance is a significant variable.
  • Displacement, velocity and power cannot be obtained.
  • Low signal to noise ratio. Sensitive to remote muscle activity and interference.
  • Low dynamic range.
  • Small sensing elements available with no influence on motion.
  • Intimate electrical contact with subject required. 

 

 

Motus Bioengineering Inc.
133 Carlisle Way,  Benicia, Calif. 94510

  Gary Felsing  707- 745-4194    Fax: 707-745-5551

e-mail: felsing@motusbioengineering.com
home page:  www.MotusBioengineering.com