There are several different kinds of capacitive stylus. But in general,
they all work by using an array of sensors to monitor the electrostatic
field around the screen. When your finger touches the screen, it
changes the electrical capacitance of that portion of the screen. This
is detected as a change in voltage at various locations. The
microprocessor captures, filters, and analyzes the data. Then
it calculates the coordinates of where the touch occurred. You can read
more about capacitive sensing here: http://en.wikipedia.org/wiki/Capacitive_sensing
When a capacitive stylus is used, the same principles apply. The only difference is
that the stylus is acting as a conductor to transmit electrical charge
between your hand and the phone. In order to function properly, a
capacitive stylus must meet several criteria.
1. A conductive surface: It must be able conduct an electrical charge
between your hand and the screen. If the material is too resistive or if
the distance between your hand and the screen is too great, the signal
reaching the screen may be too weak to be detected.
2. At least 1/4 inch wide: When filtering data, the processor ignores
areas that are significantly smaller than a human finger tip. This helps
avoid unintentional activation. Having a stylus that is about 1/4
inch wide will ensure that there is enough surface area to be detected.
3. A relatively flat end: Having a flat tip ensures that the whole face can get close enough to the screen to be detected.
4. A smooth surface: This will ensure that you don't scratch up your screen.
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