AN3150 Datasheet, PDF (12/25 Pages) Freescale Semiconductor, Inc – Soldering Recommendations for Pressure Sensor Devices

Proximity sensing electrode design
4
Proximity sensing electrode design
AN3150
Each application has its specific proximity detection requirement. The design of the
proximity sensing electrode is the result of the performance target requirement integrating
application constraints.
To help proximity sensor integrators, the following chapters provide experimental results that
can be used as guidelines to design the proximity sensing electrodes.
These tests have been performed on STM8T141 or STM8T143. The absolute performance
values like the detection distance, depend on the detection threshold setting or system gain
that are specific to the application.
4.1
Ring, spiral, plain electrode design
The performance results presented in this application note were measured using electrodes
with basic shapes. The differences between these electrodes were obtained by changing
only one parameter at a time in order to clearly show each parameter impact.
The differences between electrodes highlight the influence of:
• Electrode size with 5 mm, 10 mm, and 20 mm electrodes.
• Electrode shape with plain, spiral, and loop electrodes.
• Backside influences with grounded or non conductive electrode backside layers.
The PCB layouts used for these tests are shown in Figure 6.
• Electrodes 1, 4 and 7 include square spiral electrode shape
• Electrodes 2, 5 and 8 include square loop electrode
• Electrodes 3, 6 and 9 include full plain square electrode
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