To give a bit of background, I am working on a DIY wheel alignment just to save some money and possibly learn a thing or two. The camber/caster involves measuring an angle that is parallel to the force of gravity (pitch or roll or X or Y axis). The toe involves measuring an angle that is orthogonal to the force of gravity (yaw or Z axis).

I have a dual-axis inclinometer (this one) that measures pitch and roll. I was able to get very accurate readings for the camber. However, my thought was that rotating the inclinometer 90 degrees would allow the X/Y axes to become a Z axes. However, when I rotate it the screen itself changes to only provide measurements in the pitch/roll axes. After much more thought and looking around, I am starting to think that this inclinometer is not capable of measuring yaw because it depends on gravity to measure tilt.

  • How do these inclinometers typically work?
  • Are they independent of the force of gravity?
  • Are there particular models or methods that can be independent of gravity?
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    \$\begingroup\$ The link to your inclinometer didn't work. \$\endgroup\$ – John Birckhead Jul 27 '16 at 0:09
  • \$\begingroup\$ Just a thought, magnetometer for the toe? \$\endgroup\$ – D-on Aug 26 '16 at 3:53
  • \$\begingroup\$ There are no methods of getting "absolute" angle independent of gravity. However, there are techniques for measuring angles against a reference. \$\endgroup\$ – pjc50 Nov 24 '16 at 15:06

Inclinometer axes in general are sensitive to changes in angle when the axes are both perpendicular to the gravity vector (near zero.) As you rotate the axis from parallel to the earth's surface, the response from an axis is proportional to the sine of the angle. The difference between the sine of 0 degrees and 1 degree is .0175; between 89 degrees and 90 degrees the difference is .00015. So an inclinometer is more than 100 times more sensitive when measuring near its zero output when compared to trying to make a direct measurement of the gravity vector. This is the reason that inclinometers are generally two axis and not designed to measure high angles.

Some higher-end inclinometers work by means of a mass on a beam magnetically centered by providing a current through a coil; the coil current required to keep it centered provides the measurement. Less expensive inclinometers can have cantilevered beams and use capacitance to measure beam deflection. I'm sure there are other techniques. They all work using gravity.


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