mary zhu

Capacitive touch sensors are to achieve the principle of touch screen.

Discussion created by mary zhu on Apr 23, 2017

I read an electronic magazine in which there is a report on the capacitive touch sensors. After reading, I became interested in capacitive touch sensors. So I searched some related materials and information about this topic. Today I come to this forum to turn to you to discuss my understandings are appropriate.


Here are my personal understandings:


With the development of mixed-signal technology, you can use the noise threshold and the finger threshold of the rebound method to achieve the key switch between the state of the clean and neat conversion, making the capacitive touch sensor into a variety of consumer electronics products in the mechanical switch A practical, value-added alternative, in addition, also improve the detection circuit sensitivity and reliability.
The wide use of touch sensors has been around for years. However, with the recent development of hybrid signal programmable devices, making capacitive touch sensors become a variety of consumer electronics products in the mechanical switch of a practical, value-added alternative.
For a typical capacitive sensor, the thickness of the cover is specified to be 3 mm or less. As the thickness of the overlay increases, it becomes increasingly difficult to sense the touch of the finger. In other words, with the increase in the thickness of the cover layer, the system adjustment process will have to go from "science" to "excellence". To illustrate how to fabricate a capacitive sensor that can enhance the current technical limits, the thickness of the glass cover is 10 mm in the examples described herein. Glass is easy to use, easy to buy, and transparent, so you can see the following induction pad. The glass cover is also applied directly to white goods.

Finger capacitance

The core of all capacitive touch sensing systems is a group of conductors that interact with the electric field. Under the skin, the human body is filled with conductive electrolyte (a detrimental to the dielectric). It is the conductive properties of the fingers that make capacitive touch sensing possible.

A simple parallel plate capacitor has two conductors, which are separated by a layer of dielectric. Most of the energy in the system is directly between the capacitor plates. A little energy will leak out of the space outside the capacitor plate, and the electric field formed by these leaks is called the "edge field". Part of the problem with making a practical capacitive sensor is that it is necessary to design a set of printed wires to direct the edge field to an effective sensing area accessible to the user. Obviously, for this sensor mode, the parallel plate capacitor is not a good choice.

Putting the finger near the edge of the electric field will increase the conductive surface area of the capacitive sensing system. The additional charge storage capacity generated by the finger is the known finger capacitance CF. Sensor capacitance without finger touch is indicated by CP. In this paper, it represents parasitic capacitance.

A common misconception about capacitive sensors is that the fingers must be grounded for proper operation of the system. In fact, the reason the finger is sensed is that it carries charge, which is completely independent of whether it is floating or grounded.


Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of capacitive touch sensors. I need continual learnings.


What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.


May someone would like to help ?


thanks in advance