User guide

Getting Started with CapSense Document No. 001-64846 Rev. *A 53

Figure 3-35. Recommended Button and Slider Layout Bottom Layer

3.7.12 Shield Electrode and Water Tolerance

Fingers and water interact in a similar, but not identical, way with electric fields. There is enough difference between

the two to make possible techniques for discriminating between a touch and a spill. On printed circuit boards and flex

circuits, a practical level of water tolerance is achieved with the use of a shield electrode. These special electrodes

add no material cost to the system because they are incorporated into the same circuit board layout as the touch

sensor. The purpose of the shield electrode is to set up an electric field pattern around the touch sensors that helps

attenuate the effects of water. The shield electrode works by mirroring the voltage of the touch sensor on the shield.

To learn more about how water tolerance is achieved with a shield electrode, refer to Cypress Application Note

AN2398, Capacitance Sensing - Waterproof Capacitance Sensing

Figure 3-36. Shield Electrode Plane

1 cm

Sensor-1

Sensor-2

PCB

– Top Layer

Shield Electrode

Plane