DocID17048 Rev 3

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AN3150

Capacitive system ground

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Capacitive system ground

Having a battery supplied portable system versus a wire-grounded system affects the

sensitivity of the sensor. This is illustrated in Figure 3 which shows the difference in

detection range between grounded and ungrounded proximity sensors. Three different

electrode designs are considered (see Section 4: Proximity sensing electrode design for

more details).

Figure 3. Detection range comparison between portable and grounded system

(test performed on STM8T141)

3.1

Connected applications

From a capacitive sensing point of view, connected applications form two groups.

Group one consists of applications where the ground is directly connected to earth. With this

touch/proximity sensor sensitivity. This is the best case scenario, but mostly reserved to

some home appliances and white goods applications.

capacitance is a combination of several capacitances as shown in Figure 4. This group

includes most consumer products, for example USB powered devices.

the value is fixed, it cannot be misinterpreted as a touch or device proximity.

ai17447V2

Portable system

Grounded system

gnd

shield

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