Structure
A capacitive touch screen is primarily composed of a multi-layer composite glass screen. The inner surface and interlayer of the glass screen are each coated with a layer of Indium Tin Oxide (ITO), and the outermost layer is a thin layer of silicone glass protective layer. The interlayer ITO coating serves as the working surface, with four electrodes extending from the four corners. The inner layer of ITO is a shielding layer to ensure a good working environment.
Principle of Operation
When a finger touches the metal layer, due to the human body’s electric field, a coupling capacitor is formed between the user’s finger and the touch screen surface. Since the working surface is connected to a high-frequency signal, a small current is drawn away from the finger at the contact point. This current flows out from the electrodes on the four corners of the screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller precisely calculates the proportions of these four currents to determine the position of the touch point.
Types
There are mainly two types of capacitive touch screens:
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Surface Capacitance: This type is coated with small voltage conductive layers on one side and has limited resolution. It is often used in kiosks.
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Projected Capacitive Touch (PCT): This type uses etched conductive layers with electrode grid patterns and has a robust architecture. It is commonly used in point-of-sale transactions and is capable of multitouch. PCT can be further divided into PCT Mutual Capacitance and PCT Self Capacitance.
- PCT Mutual Capacitance: A capacitor is located at each grid intersection via applied voltage, facilitating multitouch.
- PCT Self Capacitance: Columns and rows operate individually via current meters. It has a stronger signal than PCT mutual capacitance and functions optimally with one finger.
Characteristics
- High Sensitivity: Capacitive touch screens can respond to slight touches, providing a smooth and intuitive user experience.
- Durability: The glass and protective layer design provide good durability and scratch resistance.
- Multitouch Capability: Many capacitive touch screens support multitouch, allowing users to perform complex gestures and operations.
- Limited Use Conditions: Due to its reliance on electrical conductivity, capacitive touch screens may not function well under certain conditions, such as wearing gloves or in environments with high humidity or static electricity.
Applications
Capacitive touch screens are widely used in various fields due to their excellent performance and user experience. Common applications include:
- Smartphones and Tablets: Capacitive touch screens provide intuitive and convenient control methods for users.
- Industrial Control and Medical Equipment: Capacitive touch screens offer reliable touch control in special environments.
- Automotive Navigation and Entertainment Systems: They allow drivers and passengers to more conveniently control navigation, audio, and other functions.
In summary, a capacitive touch screen is a type of touch-sensitive display technology that uses the electrical conductivity of the human body to detect touch. It has high sensitivity, durability, and multitouch capabilities, making it widely used in various fields.