Describe the basic elements of a capacitive sensor, and how a capacitive sensor

Question

Describe the basic elements of a capacitive sensor, and how a capacitive sensor works;

Review the applications of capacitive sensing in any touchscreen devices you own, such as your mobile handsets, home electronics, and computers.

This project has been designed as a thematic capstone assignment that is designed for reviewing concepts of electrostatic forces, electric fields, capacitors, and capacitive reactance. There should be specific focus on the behavior of capacitive sensors and real-life applications of these capacitive sensors.

Present a review of the related physics concepts as covered in this course.

Include a discussion of capacitors that exist in nature and various real-world applications based on the concepts and properties of the capacitive sensors.

pls provide good details and you would be reward

Explanation / Answer

For more detailed description,please go to wikipedia page.The following is just a piece copied from there :)

In electrical engineering, capacitive sensing is a technology, based on capacitive coupling, that takes human body capacitance as input. Capacitive sensors detect anything that is conductive or has a dielectric different from that of air.

Many types of sensors use capacitive sensing, including sensors to detect and measure proximity, position or displacement, humidity, fluid level, and acceleration. Human interface devices based on capacitive sensing, such as trackpads,[1] can replace the computer mouse. Digital audio players, mobile phones, and tablet computers use capacitive sensing touchscreens as input devices.[2]Capacitive sensors can also replace mechanical buttons.

Capacitive sensors are constructed from many different media, such as copper, Indium tin oxide (ITO) and printed ink. Copper capacitive sensors can be implemented on standard FR4 PCBs as well as on flexible material. ITO allows the capacitive sensor to be up to 90% transparent (for one layer solutions, such as touch phone screens). Size and spacing of the capacitive sensor are both very important to the sensor's performance. In addition to the size of the sensor, and its spacing relative to the ground plane, the type of ground plane used is very important. Since the parasitic capacitance of the sensor is related to the electric field's (e-field) path to ground, it is important to choose a ground plane that limits the concentration of e-field lines with no conductive object present.

Designing a capacitance sensing system requires first picking the type of sensing material (FR4, Flex, ITO, etc.). One also needs to understand the environment the device will operate in, such as the full operating temperature range, what radio frequencies are present and how the user will interact with the interface.

There are two types of capacitive sensing system: mutual capacitance,[3] where the object (finger, conductive stylus) alters the mutual coupling between row and column electrodes, which are scanned sequentially;[4] and self- or absolute capacitance where the object (such as a finger) loads the sensor or increases the parasitic capacitance to ground. In both cases, the difference of a preceding absolute position from the present absolute position yields the relative motion of the object or finger during that time.

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