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14
PART NO: 860029-001
Last Revised 01/06/15
8.0 CROSS-AXIS SENSITIVITY
Assuming you have stable and repeatable fixturing, and have followed all of the rules for target
mounting, pivot points, etc., under certain conditions the system may exhibit signs of error we
classify as cross-axis sensitivity.
8.1 Cross-axis sensitivity may occur under the following conditions:
The target must be one with x and y axes of tilt moving about a central pivot point (see Figure
4). When the target tilts full range in its x axis, it should be able to tilt full range in its y axis
without any change in the indicated output of the x axis (or vice versa). This may not be the
case. Cross-axis tilt can increase the coupling between the sensor and target, which causes a
slight change in output, though there is no change in the actual distance between the sensor
and target. This is a definition of error.
This error manifests itself as increased non-linearity of the output at the extreme end points of
target travel only. (This non-linearity can change overall linearity from the specified 0.1% to
about 0.3%.)
8.2 Additional points of emphasis about cross-axis sensitivity:
Again, the error manifests itself only at the end points of target travel (the last 20%) when the
target tilts fully in both x and y axes.
The degree of error is related to the angle between the sensor and target face. As a general
rule, for angles ± 1
o
or less, there is virtually no problem with cross-axis sensitivity.
Sensor/target angle is a function of the distance between the sensor and target pivot, and the
measuring range. A sensor with a range of ± 10 mils mounted 10 mils from the pivot will
experience 45
o
of tilt at the end points. This is an extreme example but suffices to illustrate the
point. A sensor with a ± 10 mil range must be mounted approximately 550 mils (13.9 mm – a
little over ½ inch) from the pivot to achieve a 1
o
angle between sensor and target.
This phenomenon is related to basic physics and is stable, repeatable, small in magnitude, and
can therefore be characterized. If necessary, users can provide a computer correction scheme.
Cross-axis sensitivity is not a problem for the majority of applications. If you anticipate or
experience the problem, contact Kaman Precision Products for test data, which specifies under
which conditions and to what degree cross-axis sensitivity exists.
