DocID17048 Rev 3

19/25

AN3150

Proximity sensing electrode design

24

Figure 13. show that the surface size is not able to compensate the influence of the GND

plane.

The size of the electrode is significantly impacting the detection range. Theoretically,

increasing the size of the electrode has two important effects:

•

by user and the electrode. This in turn improves the sensitivity.

and consequently reduces the sensitivity.

4.3

Proximity detection range versus electrode shape

The objective of this test is to measure the influence of the electrode form factor. For an

electrode surface size of 200mm², different form factors are tested. For all electrode shapes,

different dielectric thickness have been evaluated.

4.3.1

Test description

Based on a 200mm² rectangle electrode, different width and length are tested according to

Figure 14. These test have been performed with a 0.8mm and 1.6mm dielectric thickness

(T) between the electrode and the GND plane. In all test cases the whole electrode surface

is covered by the test object.

Figure 14. Test boards form factors

For each dielectric thickness, different electrode size ranging from 50mm² to 250mm² have

been tested (see Figure 11.)

MS31259V1

7.5 mm

4.7 mm

14.1 mm

3.5 mm

2.8 mm

200 mm

2