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A capacitive sensor is a proximity sensor that detects adjacent objects by measuring their effect on the sensor's electrical field. Simple capacitive sensors have been commercially available for several years and have found a niche in the detection of nonmetallic objects, although they are limited to small ranges, often less than 1 cm.
In their capacity to identify conductive materials while seeing through insulating materials like wood or plastic, capacitive sensor is akin to radar. In practise, the distinctions are significant. Capacitive sensors have the following advantages over radar:
Because they're simpler, they're likely to be smaller, less expensive, and less power-hungry.
Instead of range sensors, proximity sensors are used. They do not provide a direct indication of the detected object's distance.
What is it capable of detecting?
The capacitive sensor measures some capacitance from items in the environment that are constantly there and hence not interesting due to its non-directional nature. The sensor detects both the automobile and the ground when mounted on a vehicle. Increases in this background capacitance indicate the presence of unknown things.
Capacitive sensors sold in stores often have a range of 1 cm or less. The object capacitance approaches the background capacitance in these ranges. The capacitance change at 1 metre, on the other hand, is orders of magnitude lower and far less than the background capacitance. It's important to figure out how much background capacitance there is so it can be subtracted from the measurement.
Because the background capacitance is greater than the object capacitance,
In this mode, the sensor is more of a change-of-presence detector than a presence detector, similar to a passive infrared motion detector (PIR.) A capacitive motion detector, on the other hand, can be employed in situations where a PIR detector would incorrectly respond to apparent background changes due to its fundamentally narrow range. This is true in the suggested car safety application, where variations in the temperature background are caused by vehicle motion.
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