3.3.4 Nylon Gain Corrected
The Nylon had a wider range in button forces required so the gain correction requires larger values than the ABS
to obtain an even response.
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-1000
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Sample
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in Data Code
0
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-2500
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(a) Left Side
(b) Right Side
Figure 3-6. Nylon Gain Corrected
The downside to having the increased gain correction is the inverse response that can be seen on some button
channels while other nearby buttons are pressed. This occurs due to the mechanical nature of the button design
where the press on one button causes the other button surface to slightly flex away from the sensor coil. Since
the data moves in the opposite direction from the button press, the impact can be ignored in the application
and the baseline algorithm in the device has additional tools to handle this impact so that it does not become
an issue. That being said, cases like this can be minimized by isolating the mechanical movement as best as
possible.
Lastly, after gain correction on both materials, the difference between the two can be seen. From the graphs,
the ABS has a larger response to each force applied than the Nylon. This is partially be due to the difference
of materials but also due to the assembly of the housing. The adhesion between the PCB and button surface is
done by hand on the test units and can lead to imperfections in the design. This shows the importance of having
a tight assembly process to obtain consistent results between units.
Hardware, Software, Testing Requirements, and Test Results
Inductive Touch and Magnetic Dial Contactless User Interface Reference
Design
15
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