Working principle of capacitive touch screen

2018-11-19 15:29:58

Working principle of capacitive touch screen

 Different from resistive touch screen，Capacitive touch screens use the current sensing of the human body to work.

The sensor screen of the capacitive touch screen is a four-layer composite glass screen.The inner surface of the glass screen and the interlayer are each coated with a conductive layer，The outermost layer is a thin layer of bauxite glass protective layer.

When we touch the finger on the sensor screen，The electric field of the human body forms a coupling capacitor between the finger and the surface of the touch screen.For high frequency current，Capacitance is a direct conductor，Then the finger sucks a small current from the contact point.

Current component flows from the electrodes on the four corners of the touch screen，The controller calculates the ratio of these four currents accurately，Get the location of the touch point.

Capacitive touch screens are plated with electrodes on all four sides of the touch screen，Forming a low voltage alternating electric field in the electrical conductor。Human body electric field，A coupling capacitor is formed between the finger and the conductor layer，The current from the four electrodes flows to the contacts，The current strength is proportional to the distance from the finger to the electrode.The controller behind the touch screen calculates the ratio and strength of the current.Accurately calculate the location of the touch point，Capacitive touch screen double glass not only protects conductors and sensors，More effectively prevent external environmental factors from affecting the touch screen，Even if the screen is dirty, dusty or greased，Capacitive touch screen can still accurately calculate the touch position.

Capacitive touch screen is a layer of transparent special metal conductive material on the surface of the glass.When the finger touches the metal layer，The capacitance of the contacts changes，Cause the frequency of the oscillator connected to it to change，By measuring the frequency change, the touch position can be determined to obtain information.Because the capacitance varies with temperature, humidity, or grounding，Therefore, its stability is poor，It tends to drift.