Touch sensor works on principle of change of capacitance
due to contact by hand. Under normal circumstances the door knob or the object being
protected has a certain capacitance which is constant. When this object is touched by hand
then the capacitance changes. This type of sensing is useful to protect door knobs, safes
or any metallic item. Such systems can cause false alarms during rainy season. It is
important that this kind of sensing is not used for objects that are directly exposed to
rain as dampness can cause change in capacitance.
Some companies overcome this problem by reducing the sensitivity of the sensor and
ensuring that the rain does not fall directly on the item being protected. |
