Capacitive Vs. Resistive Touchscreens: What Are the Differences?

 According to the working principle and the medium for transmitting information, touch screens are divided into four categories: resistive, capacitive, infrared, and surface acoustic wave. Each type of touch screen has its own advantages and disadvantages. In order to understand the application of touch screens, the key factor is to understand the working principles and characteristics of each type of touch screen. Among them, resistive and capacitive touch screens currently have the best market prospects, and other technologies are difficult to catch up with in the short term. Capacitive and resistive touch screens have been widely used in our daily life, such as smartphones, tablet PCs, and other electronic products. Then, what are the differences between capacitive and resistive touch screens, and which is better? 

1. What is a capacitive touch screen?

A capacitive touch screen works by using the human body\’s current induction. It is a four-layer composite glass screen. The inner surface of the cover glass and the interlayer are each coated with a layer of ITO. The outermost of the cover glass is only a 0.0015mm protective layer of silica glass. The two ITO layers are served as the working layers, which are shielded to ensure a good working environment, and four electrodes are led on the four corners. 

2. The working principle of capacitive touch screens

A capacitive touch screen is commonly known as a \”hard screen\”. When fingers touch the metal layer, a coupling capacitance will be generated between the finger and the touch screen\’s surface due to the human body\’s electric field. For high-frequency currents, the capacitance is a direct conductor. Thus, the finger draws a small current from the touch point. The current flows out of the electrodes on the four corners of the touch screen respectively, and the values of the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller can determine the touch point by calculating the precise ratio of the four currents. 

3. What is a resistive touch screen?

 A resistive touch screen is commonly known as a \”soft screen\”. A resistive touch screen is two layers of the mutual insulation film, one layer of resistance and the other layer can be considered a pure conductor. By pressing the two layers of film contact to change the resistance value potential, the location of the touch point is determined. 

4. The working principle of resistive touch screens

Pressure is used to control the progress of resistive touch screens, the main part of which is a multi-layer composite resistive film that matches the surface of the display very well. It uses a hard plastic plate or glass as the base layer. The outer surface is coated with a transparent metal oxide (transparent conductive resistor) conductive layer. It is covered with a hardened, smooth, scratch-resistant plastic layer coated on the inside and outside surfaces. There are many fine (less than 1/1000 inch) transparent isolation points between these coatings, separating the two conductive layers from each other. When the finger touches the screen, the two conductive layers come into contact at the touch point, where the resistance changes. Signals are generated in the X and Y directions, which are then transmitted to the touchscreen controller. The controller detects this contact, calculates the position (X, Y), and then operates according to the simulation of the mouse. This is the most fundamental working principle of resistive touch screens. The key to making resistive touch screens lies in materials. Commonly used transparent conductive coating materials include:

  A, ITO, indium oxide, weak conductor. When the thickness drops below 1800 angstroms (angstroms = 10-10 meters), it will suddenly become transparent( the light transmittance is 80%). The light transmittance decreases when the thickness continues to fall and rises to 80% when the thickness reaches 300 angstroms. ITO is the primary material used in all resistive and capacitive touch screens, the working surface of which is ITO coating.

B, Nickel-gold coating. The outer conductive layer of 5-wire resistive touch screens is made of nickel-gold coating material with good flexibility. Since the outer conductive layer is frequently touched, the purpose of using nickel-gold material with good flexibility is to prolong its service life. But the cost of the process is high. Although the nickel-gold conductive layer has good flexibility, it can only be used as a transparent conductor, which is unsuitable for the working face of resistive touch screens. Due to its high conductivity, and the metal is not easy to be processed with uniform thickness, it is not suitable for the voltage distribution layer but can only be used as a probe layer.

5. Two categories of resistive touch screens

5.1 4-wire resistive touchscreen

When two transparent metal layers of 4-wire resistive touch screen work, the voltage of each layer increases by 5V: one vertical and one horizontal. A total of 4 wires are needed.

Features: High resolution, high-speed transmission response. Exterior hardness treatment, scratch-reducing, scratches, and chemical protection. With glossy and matte treatments. One-time calibration, high stability, and never drift.

5.2 5-wire resistive touchscreen

In the base layer of 5-wire resistive touch screens, voltage fields in two directions are applied to the conductive glass working surface through a fine resistance network. We can simply consider that the voltage fields in two directions work, which are applied to the same working surface at different times. The outer nickel-gold conductive layer is only used as a pure conductor. When the screen is touched, the X-axis and Y-axis voltages of the inner ITO touch point are measured at different times to determine the position of the touch point. The inner ITO of the 5-wire resistive touch screens needs four wires, and the outer layer only serves as a conductor that needs one wire. Therefore, there are five leading wires for 5-wire resistive touch screens.

Features: High resolution, high-speed transmission response. High exterior hardness, scratch-reducing, scratches, and chemical protection. The same point can be touched more than 30 million times. The conductive glass is the medium of the substrate. One-time calibration, high stability, and never drift. 5-wire resistive touch screens have a high price disadvantage because of the highly complex manufacturing process.

5.3   Limitations of resistive touch screens

Whether a 4-wire resistive touch screen or a 5-wire resistive touch screen, they have a completely isolated working environment from the outside world, which are resistant to dust and water vapor. Any object can touch it, which can be used for writing and drawing. It is more suitable for industrial control fields and workers in offices. The common disadvantage of resistive touch screens is that the outer layer of the composite film is made of plastic material. Too much force or touching with a sharp instrument may scratch the whole touch screen and lead to its scrapping. However, within limits, scratches will only hurt the outer conductive layer, which is acceptable to 5-wire resistive touch screens but fatal to 4-wire resistive touch screens.

6. Advantages of capacitive touch screens 

1. Capacitive touch screens require only touching without pressure to generate signals.

2. Capacitive touch screens require only one or no calibration after production, while resistive touch screens require routine calibration.

3. Capacitive touch screens have a longer serving time because the components in capacitive touch screens do not need to be moved. In resistive touch screens, the ITO film on the upper layer must be thin enough to be elastic to bend down and contact the ITO film below.

4. Capacitive technology is superior to resistive technology in optical loss and system power consumption.

5. The selection of capacitive or resistive technology mainly depends on the object touching the screen. The capacitive touch screen is a better choice if fingers touch the screen. The resistive touch screen is capable if a stylus is needed, whether it is plastic or metal. A stylus can also be used on capacitive touch screens, but it should be special to match the screen.

6. Surface capacitive touch screens can be used for large-size touch screens, which have a low cost but do not support handwriting recognition. Projective capacitive touch screens are mainly used for small and medium-sized, which can support handwriting recognition.

7. Capacitive touch screens have the advantages of wear resistance, long service life, and low maintenance cost. Therefore, the overall operating cost of the manufacturers can be further reduced.

8. Multi-touch technology can be supported by capacitive touch screens, which are not as slow as resistive touch screens. Moreover, they are challenging to be worn out.

7. Disadvantages of capacitive touch screens

1. The transmittance and clarity of capacitive touch screens are superior to that of 4-wire and 5- wire resistive touch screens. However, surface acoustic and infrared touch screens have better transmittance and clarity than capacitive touch screens. Moreover, the transmittance of the four-layer composite touch screen with capacitive technology is not uniform for each wavelength of light, and there is color distortion. Due to the reflection of light between each layer, the image characters may be blurred.

2. Current: In principle, a capacitive touch screen uses the human body as an electrode of a capacitor element. When there is enough capacitance between the conductor and the interlayer ITO working face, the current flowing away is enough to cause the misoperation of capacitive touch screens.

When the display is held with your hand, the palm is within 7 cm of the display, or the body is within 15 cm of the display, misoperation of the capacitive touch screen may be caused.
Although the capacitance value is inversely proportional to the distance between electrodes, it is directly proportional to the relative area and is also related to the insulation coefficient of the dielectric. Therefore, misoperation of the capacitive touch screen can be caused when a large palm or hand-held conductor is close to the capacitive touch screen instead of touching it. This is especially serious in humid weather. When the display is held with your hand, the palm is within 7 cm of the display, or the body is within 15 cm of the display, misoperation of the capacitive touch screen may be caused. Another disadvantage of capacitive touch screens is that they do not respond when touched with thickly gloved hands or non-conductive objects. This is due to the more insulating medium.

3.  Drift: The main disadvantage of capacitive touch screens is drift. When the ambient temperature, humidity, and the ambient electric field changes, drift on capacitive touch screens will occur, resulting in inaccuracy. For example, after starting up, the temperature rise of the dispaly may cause drift; When the user touches the screen with one hand, if the other hand or one side of the body is close to the display, drift may occur; Drift may occur when large objects near the capacitive touch screen are removed; When the user touches the screen, if someone comes around to watch, it may also cause drift. The drift of the capacitive touch screens is a congenital technical deficiency. Although the potential ambient surface (including the user\’s body) is far away from capacitive touch screens, it is much larger than the area of fingers. They can directly impact the measurement of the position of the touch point. 

4. In theory, many relationships that should be linear are actually nonlinear. For example, The total amount of current sucked by people with different weights or wet fingers is different. The change in total current and the changes of four sub-currents are nonlinear. Capacitive touch screens use the four-angle self-defined polar coordinate system with no origin. Moreover, after the 4 A/D (analog to digital converter) complete their work, the calculation process from the four sub-currents to the X and Y values of the touch point in the rectangular coordinate system is complicated. Therefore, the controller cannot detect the drift and recover it. Since there is no origin, and the drift of capacitive touch screens is cumulative, calibration is often needed in the work site. The protective silica glass on the outermost surface of capacitive touch screens is very scratch-resistant, but it is fragile to being knocked by nails or hard objects. If you knock out a small hole in the screen, it will hurt the interlayer ITO. Whether it hurts the interlayer ITO or the inner surface ITO layer during installation and transportation, capacitive touch screens can not work normally.

5. Low accuracy: Due to technical reasons, the accuracy of capacitive touch screens is lower than resistive touch screens. Moreover, it can only be touched with fingers, in which complex handwriting input on a small screen is challenging to be recognized. 

6. The cost will be higher: There still are some technical difficulties for capacitive touch screens to be bonded to LCD panels. Full lamination(optical bonding) is required during the process, so the cost is higher.

8. Advantages of resistive touch screens

The advantages of resistive touch screens are that the screens and the control system are relatively cheap and have high response sensitivity. Moreover, whether it is a 4-wire resistive touch screen or a 5-wire resistive touch screen, they have a completely isolated working environment, which is resistant to dust and water vapor and can adapt to various harsh environments. It can be touched by any object and has good stability.

The advantages of resistive touch screens are as follows:

1. The resistive touch screen has high accuracy, reaching the pixel level, and the applicable maximum resolution can reach 4096×4096.

2. The screen is resistant to dust, water vapor, and oil pollution and can be used in lower or higher-temperature environments.

3. Pressure is used to control the progress of resistive touch screens, which can be touched with any object. It can be operated with gloved hands and even be used for handwriting recognition.

4. Resistive touch screens are cheap because of their mature technology witha low technology entry threshold.

9. Disadvantages of resistive touch screens

The outer film of resistive touch screens is easily scratched, which makes the touch screen unusable. A multi-layer structure can lead to a lot of light loss. For handheld devices, it is usually necessary to increase the backlight\’s brightness to compensate for poor light transmission. But this will also increase power consumption.

Disadvantages of resistive touch screens can be classified as:

1. It feels terrible when it is compared with capacitive touch screens. People are lazy. We have to not only touch the panel\’s surface but also give a little pressure, so it can finally work. On the contrary, capacitive touch screens have an excellent user experience. It will work when you only touch with no resistance obstacle.

2. Light transmittance is not so good, and it is a little bit dark on the surface, especially when it is 3-layer Resistive Touch Screen or 4-layer Resistive Touch Screen.

3. It is easy to be damaged because it has a soft surface. The surface hardness is only 2H or 3H. When our fingers touch the surface, the first layer (PET or ITO film) will be deformed by the pressure. Theoretically, it can only serve 100 thousand to 1 million drawing times.

4. It is not very accurate after a long time serving because the first layer (PET or ITO film) has been partly damaged. That is why we have to adjust the contact points from time to time.

5. Resistive touch screens can be designed for multi-touch. However, when two points are pressed at the same time, the pressure on the screen becomes unbalanced, resulting in touch errors. Therefore, it is challenging to realize multi-touch. We usually realize this function with capacitive touch screens.

10. Difference between resistive touch screens and capacitive touch screens

 1. Cost

The manufacturing cost of capacitive touch screens is generally 10% to 50% higher than that of ordinary resistive touch screens. Therefore, the former is seen on many high-end devices, while the latter is more used in low-end devices.

2. Service life

① Resistive touch screens:

Service life: ≥ 1,000,000 times
Life of drawing lines: ≥100,000 times

② Capacitive touch screens:

They can sense light touch and are convenient to be used. Moreover, the contact between fingers and the touch screen will almost not wear out the screen, and the performance is stable. After the mechanical test, the service life is tested to be as long as 30 years.

3. Touch sensitivity

① Resistive touch screens:

Pressure is needed to make each layer of the screen contact. You can use your fingers (even if you wear gloves), nails, stylus, etc., to touch the screen.

② Capacitive touch screens:

The slightest contact from the surface of the fingers can also activate the capacitive sensing system under the screen. Non-living objects, nails and gloves cannot be sensed by the screen. Handwriting recognition is difficult to be achieved.

4. Precision

① Resistive touch screens:

The accuracy reaches at least a single display pixel, which can be seen when using a stylus. Handwriting recognition is easy to be achieved, which is helpful for operating under the interface with small control elements.

② Capacitive touch screens:

The theoretical accuracy can reach several pixels, but it is actually limited by the finger contact area, so it is difficult for users to accurately click on targets less than 1cm2.

5. Feasibility of point touch

① Resistive touch screens:

Resistive touch screens only support single touch, so they can only recognize and support the touch of one finger at a time. If more than two points are touched at the same time, the screen cannot make the correct response.

② Capacitive touch screens:

The multi-touch technology supported by the capacitive touch screens can significantly facilitate the actual operation. Moreover, it is sensitive and anti-wear, which is more suitable for entertainment and games. Users can touch the screen with both hands when zooming in and out pictures and web pages. They can also touch the screen with different gestures such as clicking, double-clicking, translating, pressing, scrolling, and rotating, so as to control the screen as they wish, thus better and more comprehensively understanding the relevant characteristics of the target (texts, videos, pictures, satellite photos, 3D simulations, and other information).

6. Wear resistance

① Resistive touch screens:

The fundamental characteristics of resistive touch screens have determined that the top is soft and can be pressed down. It makes the screens very prone to be scratched. Resistive touch screens need protective film and relatively more frequent calibration. On the positive side, resistive touch-screen devices using plastic layers are generally less likely to wear and break.

② Capacitive touch screens:

Tempered glass can be used as the outer layer. Although this is not indestructible and may break under severe impact, the glass is more resistant to scratches and stains.

7. Cleaning and maintenance

① Resistive touch screens:

Since a stylus is needed to touch the resistive touch screen, it is not easy to leave fingerprints and bacteria on the surface of the screen. However, the soft texture makes it easy to be scratched, and the frequency of changing the screen protector is high.

② Capacitive touch screens:

They are touched by fingers, which are easy to be cleaned. In addition, tempered glass is used in some high-end models so that the screen is not easily damaged.

8. Environmental adaptability

① Resistive touch screens:

 They almost have no requirements for the external environment and can work under any conditions. It is suitable for industrial control products with high environmental requirements. 

② Capacitive touch screens:

They are relatively \”delicate\” and have strict voltage, temperature, and humidity restrictions. It is suitable for consumer electronics products that do not have high environmental requirements.

9. Visual effects indoors and outdoors

The indoor effect for both is very good, and there is little difference.

① Resistive touch screens:

In outdoor environments, they reflect a lot of sunlight, and the visual effect is far inferior to that of capacitive touch screens.

② Capacitive touch screens:

The manufacturing materials will absorb light, so the visual effect outdoors will be excellent.

11. Summary

Although capacitive touch screens are better than resistive touch screens, there are still many users who cannot accept capacitive touch screens. Some people think capacitive touch screens are prone to misoperation, especially when browsing web pages. When browsing a web page with many links, at least three links will be clicked if you touch the screen with your thumb. However, nails cannot be sensed by the screen. The feeling is even worse in summer when your hands are sweaty. You are likely to misoperate the screen when you input with a complete virtual keyboard. When you unlock the screen, the screen will respond to your slight touch. Therefore, the selection of capacitive or resistive touch screens depends on the needs of different people.