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.