What are the classifications of resistive touch screens?
What are the classifications of resistive touch screens?The core principle of resistive touch screens is to locate...
What are the classifications of resistive touch screens?
The core principle of resistive touch screens is to locate the pressed point by the contact between two conductive layers. Their classification primarily depends on the number of internal leads and structural design. The following provides a detailed breakdown and explanation of the classification:
Main classification (by number of lines)
This is the most common and core classification method, which directly determines the performance, accuracy, and cost of the screen.
1. Four-wire resistive screen
Structure: Two conductive layers of ITO (indium tin oxide) are stacked on top of each other. The X+ and X- electrodes of the upper layer (touch layer) are located on the left and right sides; the Y+ and Y- electrodes of the lower layer (base layer) are located on the top and bottom sides.
Working Principle:
First, apply a voltage between the upper X+ and X- electrodes to form a uniform electric field in the X direction. Then, detect the X coordinate of the touch point by measuring the voltage of the lower Y electrode.
Then, a voltage is applied between the lower Y+ and Y- electrodes to form a uniform electric field in the Y direction. The Y coordinate of the touch point is detected by measuring the voltage of the upper X electrode.
Advantages: simple structure, lowest cost.
Disadvantages:
The upper ITO film, which serves as both a conductive layer and a touch surface, is prone to wear and tear due to scratches or repeated bending, resulting in poor durability.
It cannot measure both X and Y coordinates simultaneously, and its anti-interference ability is slightly weak.
Applications: Early PDA, lower-end industrial control equipment, and applications that are extremely cost-sensitive.
2. Five wire resistive screen
Structure: This is currently the mainstream technology. All electrodes (X+, X -, Y+, Y -) are fabricated on the underlying glass substrate. The upper film only serves as a pure conductor (voltage probe) and does not undertake any current transmission tasks.
Working principle: Apply voltage alternately on the four electrodes of the glass substrate to form a uniform voltage field on the surface of the glass. The upper film is only responsible for "conducting" the voltage of the touch point back to the controller for measurement. By measuring this voltage value, the controller can calculate the X and Y coordinates.
Advantages:
Extremely durable: Because the key electrodes and ITO layer are on a hard glass substrate, even if the upper film is scratched or worn, as long as it is not penetrated, it will not affect the positioning accuracy.
High precision and good stability.
Support single touch (gesture).
Disadvantage:
The cost is higher than that of a four wire model.
Applications: Medical equipment, industrial control systems, POS machines, high-end handheld terminals, and other fields that require high reliability and long lifespan.
3. Eight wire resistive screen
Structure: It can be understood as adding a pair of "detection lines" to each electrode (X+, X -, Y+, Y -) on the basis of the four wire type, for real-time monitoring and compensation of resistance drift caused by environmental temperature changes, voltage fluctuations, or long-term use.
Advantages: Precision and stability are the highest among resistive screens, effectively avoiding the phenomenon of "drift".
Disadvantages:
The highest cost, slightly complex circuit and driver.
Application: Special occasions with extremely strict precision requirements, such as certain military or precision measuring equipment.
Other classification dimensions
1. According to surface hardness
Soft screen: The touch surface is made of soft PET film. It has a soft touch and is prone to scratches, but it has good impact resistance.
Hard screen: Covering a layer of hardened coating on PET film to make the surface more wear-resistant, scratch resistant, and feel closer to glass.
2. According to transmittance
Standard type: The transmittance is usually around 75% -85%.
High transparency type: Using materials and processes with better optical performance, the light transmittance can reach over 85%, making the bottom display screen look clearer and brighter.
3. According to the installation method
Plug in: As an independent module, installed in front of the display screen. Flexible installation, but usually with thicker borders and air layers.
Embedded/On Cell: Integrating the sensor of the resistive screen more tightly into the display module can reduce overall thickness and reflection, and improve visual effects.
4. Hybrid touch screen
This is not a pure resistive screen, but a combination technology. For example, "resistor capacitor" uses low-power capacitive sensing (for wake-up) during standby and high-precision resistive positioning during operation. This type of product is relatively rare.
Summary comparison table
Feature | Four wire resistive screen | Five-wire resistive screen | Eight wire resistive screen |
Cost | Minimum | Moderate | Most expensive |
Durability | Lower (upper membrane vulnerable) | Extremely high (electrode on glass) | high |
Precision | average | high | Extremely high (with automatic compensation) |
Anti-interference | average | good | Very good |
Mainstream applications | Low cost, lightweight applications | Industrial, medical, and commercial mainstream | High precision special fields |
Selection recommendation
Pursuing extremely low cost and low requirements for lifespan: optional four wire type.
The vast majority of industrial and commercial applications require reliability, durability, and precision: the five wire type is the preferred choice.
Environmental conditions are harsh, temperature differences are large, and absolute precision stability is required: consider the eight wire type.
Simultaneously requiring precise operation with a stylus and finger touch: resistive screens (especially five wire ones) are still an excellent choice.
I hope this detailed classification can help you fully understand resistive touch screens.
