Electrical Goniometer Theory - Noraxon Ultium 808 User Manual

2D Goniometer SmartLead User Manual
In general, there are no fixed rules governing which size of sensor is most suitable for a particular
joint; this depends on the size of the subject. The sensor must be capable of reaching across the
joint so that the two endblocks can be mounted where least movement occurs between the skin and
underlying skeletal structure. In certain circumstances more than one size of sensor will be
appropriate. The following table is given for guidance only and refers to an adult population.
JOINT
wrist
forearm
elbow
ankle
knee
hip
back
back
neck
neck
finger DIP, PIP, MCP
toe
Single Axis Goniometer F35
Measures angles about x-x axis

15.1 Electrical Goniometer Theory

The working mechanism is the same for all three types of sensor (F35, SG, Q). Between the two
endblocks there is a protective spring. Inside this spring is a composite wire that has a series of
strain gauges mounted around the circumference. As the angle between the two endblocks varies
(Fig. 1), the change in strain along the length of the wire is measured and is equated to angle. Only
angular displacements are measured. If the two ends move linear relative to each other (Fig. 2),
(Rev D January 2020)
SENSOR MEASURED OUTPUT
SG65 or SG75 flexion/extension, radial/ulnar deviation
Q110 or Q150 pronation/supination
SG110 flexion/extension
SG110 or SG110/A dorsiflexion/plantarflexion, inversion/eversion
SG150 flexion/extension
SG150 flexion/extension, abduction/adduction
SG150/B flexion/extension/lateral flexion
Q150 axial rotation
SG110 flexion/extension, lateral flexion
Q110 axial rotation
F35 flexion/extension
F35 flexion/extension
Single Axis Torsiometers Q110 and Q150
Measures rotations in one plane
Twin Axis Goniometer Sensors SG Series
Measures angles simultaneously in two planes
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