Resistive screen operating principle. Capacitive and resistive touch screens

More recently, the mobile device market could offer mainly push-button devices. Only occasionally did people find themselves in the hands of PDAs and other gadgets that had a touch screen. But times change, and technology does not stand still. Now the counters have almost completely gotten rid of push-button devices, providing a huge selection touch phones and tablets. At the same time, the variety of shapes, models and quality of gadgets is simply amazing. But they all have the same principle of input and output of information - a touch screen, which also has its own varieties. Let's look at what a touchscreen is, what types there are, and how to calibrate them.

Types of sensors

From the very beginning, let's define a touchscreen. A touchscreen is a device for entering any information into a phone or tablet. It is intended for the device to adequately perceive orders. Often a touchscreen (or sensor) is confused with a screen, but these are completely two different things.

The market today offers 4 main types of sensors for mobile devices:

• resistive;
• induction;
• capacitive;
• infrared.

They can be found at the most various devices and, in turn, their cost partially depends on the type of touchscreen. Let's take a closer look at each of them.

Resistive touchscreen

The resistive type of touchscreens works on the principle of responding to changes in geometric parameters. So, to get a response from the screen, you need to press it lightly. For this reason, we can immediately say about the disadvantages that a resistive touchscreen has. That this is a bad indicator is an understatement. It's all about the pressure itself, which causes the screen to deteriorate greatly. And although it’s quite easy to work with such a touchscreen with gloves or a stylus, the image turns out faded and scratches appear after a while.

Induction touchscreen

This type of touchscreen is located behind hard glass and can only be controlled using a special stylus. This is very inconvenient, since if this item is lost or broken, you will need to spend a considerable amount of money to purchase it.

Capacitive touchscreen

This type of touchscreen can be called an improved form of resistive sensors. It's also on top of the screen itself and spoils the image a bit. You can use either a stylus or your fingers to control it. It is possible to support multi-touch (which the previous options do not have) and the operating principle is based on the difference in electrical resistance. This allows you to enter information only when lung help touch. The disadvantage is that it is impossible to control third-party objects and gloved fingers.

Infrared touchscreen

These sensors work on the principle of an infrared grid. Infrared touchscreens are universal. They do not spoil the image, but, in turn, have a long response time and low accuracy.

Approximately 80% of touch devices use a capacitive sensor. It is as convenient as possible, inexpensive and at the same time has high response rates. Resistive is less common, but it is also used in mobile devices due to its cheapness.

Touchscreen calibration

In some cases, when replacing a sensor or when malfunctioning, calibration is required. This procedure is not very complicated, but requires maximum attention, since the correct response of the touchscreen depends on it.

Touchscreen calibration is a sensor adjustment procedure that is carried out to improve the accuracy of the response to touching the device. To check whether this procedure is required or not, you need to remove protective film(if it’s not there, wipe the screen well), turn on any text editor and click on a specific letter. If a different sign appears on the screen instead of the selected option, calibration is required.

Calibration of resistive sensors

Typically resistive touch screens Immediately when you turn it on for the first time, you are asked to calibrate the touchscreen. Almost everyone forgets that this is a necessary monthly procedure after turning it on for the first time. Also, calibration must be carried out when replacing the screen, software failure, after a fall or impact.

It’s quite easy to calibrate a resistive sensor thanks to a built-in utility called ts_calibrate. To launch it, you need to go to the “Settings” section in the menu of your phone or tablet. Next, select “Phone Settings” and click on “Calibration”. As a result of these actions, the screen will turn black and a cross with a red dot located in the center will appear on it.

To calibrate a resistive touchscreen for a phone or tablet, you need to press the spot indicated by the dot. After each response, it moves and after the fourth press, all data about the grid is saved in the device’s memory. You can check after calibration using text input. If everything was done correctly, the specified letter or number will appear on the screen.

Capacitive Sensor Calibration

Quite rarely, but there are cases when capacitive sensors also have a grid that gets lost and needs to be calibrated. The problem lies in the procedure itself, since these touchscreens have a very complex design and the devices do not have built-in software.

Calibration must begin by downloading the TouchScreen Tune utility. It easily identifies and configures the touchscreen itself. What will this give? It’s just that in cases of a software failure or sensor replacement, it is impossible to independently set a grid that would work adequately. Thanks to this program, you can adjust everything to the desired values.

Additionally, it is worth noting malfunctions in the operation of the G-sensor, which determines the position of the smartphone or tablet in space. In some cases, it behaves inappropriately and makes using the gadget very difficult.

To calibrate the accelerometer of a device running Android OS you need:

1. Go to engineering menu and simultaneously press the power button and volume down button.
2. After the menu appears on the screen, using the same volume button, you need to scroll through the positions and find the Test Report item.
3. In the list that opens, select G-Sensor cali.

After that, simply place the gadget on a flat surface and click on Do Calibration. You need to wait until the digital values ​​stop appearing on the screen. Then press the volume up button twice and select Reboot. The accelerometer has been calibrated.

Precautions

It is necessary to calibrate the resistive touchscreen for tablets and phones once a month, since active use devices quickly disrupts the entire grid. If you do not do this, you may end up with an inadequate response to pressure and inconvenience in use. But, as a rule, there are no problems with calibration in this case.

Things are much more complicated with capacitive sensors. They do not initially imply calibration as a quality standard procedure. For this reason, before you begin, you need to understand that if the calibration is carried out with great violations, it will not be possible to return all the original settings that the touchscreen had. What does it mean? This total loss functionality of the device, which is almost impossible to restore even in service centers. Therefore, calibrating a capacitive sensor is only necessary if you are confident in your abilities and skills.

Smartphone users who do not speak English well are puzzled when they hear the name “touchscreen” - what part of the phone is this? This is usually the name given to any touch screen, regardless of what device it is installed on. Currently, such displays are used not only for mobile gadgets, but are also built into various self-service terminals.

What is a touchscreen?

This term comes from the merger of two English words: touch and screen, which means “touch screen”. This display responds to touch and makes it easier to control equipment. However, it is worth distinguishing between several types of equipment, since the principle of their operation is not entirely similar.

IN modern gadgets, for example, on the iPhone, capacitive and projected-capacitive displays are installed. The latter type can be called more advanced, since it is capable of reading a certain number of touches simultaneously. These touchscreens themselves are glass panels with a layer of resistive material and electrodes.

There are also displays on which a flexible membrane is applied. Between it and the glass there are micro-insulators, pressing on which provokes a change in resistance. It is captured by the controller and converted into coordinates, resulting in control of the device.

The main difference between these types of technologies is that a capacitive display does not respond to touch with any object or even a simple stylus, which cannot be said about a resistive touchscreen. Thus, locking a smartphone on it works much better than on its outdated “brother”.

How different screens work

There are only 3 types Touch Screen, 2 of which have already been briefly described:

• capacitive;
• wave;
• resistive.

It's worth starting with the most used one, i.e. capacitive display. How does such a screen work on a phone? It's quite simple. The resistive layer serves as a charge accumulator that the electrodes pass through, while the user, with his touch, pushes out some of the energy at a certain point. This works due to the fact that there is also current in the human body. When the charge level decreases, this change is recorded by the microcircuits and transmitted to the touchscreen driver.

The main advantage of such displays is that they are quite wear-resistant. Over time they do not lose their original brightness and are able to transmit clearer images.

The principle of operation of a resistive screen was described above. If we look at this in more detail, we should say that a flexible membrane is an elastic metal plate that passes current. Between it and the conductor layer there is empty space. When interacting with the display, the user presses lightly on its surface, closing the membrane with the conductor at this point. Then everything happens according to the same scheme: the system reads the coordinates, and the driver issues commands to the OS.

Resistive displays have not been popular for a long time, since their functionality is somewhat limited compared to capacitive touchscreens. Such screens can only be found in very outdated technology or various terminals, but less often.

What is a wave touchscreen? It is also a glass surface with a coordinate grid and transformers. One of them transmits impulses, while the other receives signals reflected by the reflector. Thus, the charge “walks” through the transducers, creating an acoustic wave, which the user interrupts by pressing. This is how the location of the touch is determined.

This type of display is the best option for artists and graphic designers, because it does not distort the image due to the lack of metal coating. It is also the most expensive, while many attribute it to the technologies of the future, believing that even a capacitive display will go into oblivion, giving way to wave technology.

Video review: types of touchscreen

Nowadays you won’t surprise anyone with a touch screen. Moreover, it is already strange to see devices without a sensor, especially when it comes to mobile gadgets. This is due to the desire to increase the working surface area. But how often do we think about what type of display is used in a particular device? Has it ever happened that, having bought new tablet or a smartphone, we try to control it using the usual digital pen, but bad luck, the device simply does not respond to its touch. Apparently, the screen is made using a different technology, capacitive, which is gradually beginning to displace its predecessor, the resistive type display.

You can meet large number touch displays, differing not only in design features, but also in their operating principle. Today there are following types touch screens: resistive, capacitive, projected capacitive, matrix, surface acoustic wave touch screen, infrared, strain gauge, inductive.

IN present moment There are two main types of touch screens used in electronics: resistive and capacitive. We will talk about them in more detail, and also try to highlight the strong and weaknesses everyone.

First, let's look at the operating principle of a resistive touch screen. It consists of a glass panel and a flexible plastic membrane, on which a resistive coating is applied. The space between the glass and the membrane is filled with micro-insulators, which in turn reliably insulate the conductive surfaces, evenly distributed over the active area of ​​the screen. When you press the display, the panel and membrane close, and the controller using analog-to-digital converter registers changes in resistance, converting them into contact coordinates. It is for this reason that such a screen can be pressed with any hard object, it can be a fingernail, a special stylus, or even an ordinary pencil. As a consequence of this structure, resistive screens gradually wear out, which is why there is a need for periodic calibration of the screen so that when you press the display, the coordinates of the touch point are correctly processed.

There are four-, eight-, five-, six- or seven-electrode screens. The simplest to manufacture, and therefore the cheapest, are four-electrode ones. They can withstand only 3 million clicks at one point. Five-wire ones will already be much more reliable - up to 35 million clicks; in them, four electrodes are located on the panel, and the fifth is located on a membrane, which is coated with a conductive composition. It is worth noting that five-wire and subsequent versions of six- and seven-wire screens continue to work even if part of the membrane is damaged.

Advantages

The advantages of a resistive screen include the low cost of its production, and, consequently, the low cost of the device in which it is used. In addition, it is worth noting that the sensor response here does not depend on the condition of the screen surface; even if dirty, the touchscreen remains just as sensitive. It should also highlight the accuracy of hitting desired point, because a dense lattice of resistive elements is used.

Flaws

As a disadvantage of resistive screens, we highlight low light transmission, no more than 70% or 85%, so increased backlight brightness is required. It is also low sensitivity, i.e. Simply touching with your finger is not enough, pressure is required, so you cannot do without a digital pen or long nails. This type in most cases it does not support multi-touch, i.e. the screen only understands one touch. When interacting with the screen, you need to make some effort to transmit any command, and if you overdo it, you can not only scratch it, but also damage the display. As mentioned above, for proper functioning it is necessary to periodically calibrate the screen.

Capacitive touch screen

The capacitive screen is glass panel, which is coated with a transparent resistive material that typically uses an alloy of indium oxide and tin oxide. Electrodes are installed at the corners of the panel, supplying low-voltage power to the conductive layer. alternating voltage, they monitor the flow of charges in the screen and transmit data to the controller, thus determining the coordinates of the touch point. Before touching, the screen has some electric charge; when touched with a finger, a point appears on the conductive layer, the potential of which is less than the potentials of the electrode, since the human body has the ability to conduct electric current and has a certain capacity. There are no flexible membranes on the screen, which ensures high reliability and allows you to reduce the brightness of the backlight. This type of screen is capable of simultaneously determining the coordinates of two or more touch points, which means multi-touch support.

Projection-capacitive screens have become a subtype of capacitive screens. They work on a similar principle. The difference is that the basic elements in them are not located on outside screen, but on the inside, making the sensor more protected. This type of display is mainly used in modern mobile devices.

Interaction with a capacitive screen should only be carried out with a conductive object, a bare finger or a special stylus that has electrical capacitance. The number of clicks before the sensor elements fail reaches more than 200 million times.

Advantages

One of the advantages of capacitive screens is that even in bright sunshine, visibility remains quite good, which cannot be said about a resistive screen, since it reflects a lot of ambient light. Another advantage was the ability to quickly and accurately recognize touch without using additional accessories. The undoubted advantage of screens of this type is more long time sensor service compared to the previous type. A “multi-finger” interface or multi-touch has also appeared, although not all devices with a screen of this type are fully implemented.

Flaws

The negative aspects of using a capacitive touch screen include a higher cost due to the complexity of production. Interaction with the display is only possible by touching a material that is a conductor. For this reason, special capacitive styluses or gloves are purchased to work with it; this becomes especially important in cold weather, and this is another expense item.

To summarize, let us recall that resistive screens are pressure sensitive, while capacitive screens are touch sensitive. The accuracy of capacitive displays is comparable to that of resistive displays, but capacitive type is characterized by higher reliability due to the absence of a flexible membrane, and a smaller number of layers makes them more transparent.

There is an opinion that resistive displays have already outlived their usefulness, and the future belongs to capacitive displays. Indeed, the transition from mechanical-electrical input to electrical already means a lot, since the accuracy of determining coordinates has increased, and multi-touch has appeared.

However, today there are still a large number of devices with resistive screens on the electronics market, but they are slowly beginning to be replaced by gadgets with capacitive sensors. Observing this trend, one can assume that the former will soon disappear altogether.

iPhone 2G was the first mobile phone, the control of which was entirely based on interaction with the touch screen. More than ten years have passed since its presentation, but many of us still do not know how the Touchscreen works. But we encounter this intuitive input tool not only in smartphones, but also in ATMs, payment terminals, computers, cars and airplanes - literally everywhere.
Before touchscreens, the most common interface for entering commands into electronic devices were various keyboards. Although they seem to have nothing in common with touchscreens, in fact, how similar a touchscreen is to a keyboard can be surprising. Let's look at their device in detail.

The keyboard is printed circuit board, on which several rows of switches-buttons are installed. Regardless of their design, membrane or mechanical, when you press each of the keys, the same thing happens. There is a short circuit on the computer board under the button. electrical circuit, the computer registers the passage of current in this place of the circuit, “understands” which key is pressed and executes the corresponding command. In the case of a touch screen, almost the same thing happens.

There are about a dozen different types of touch screens, but most of these models are either outdated and not used, or are experimental and are unlikely to ever appear in production devices. First of all, I will talk about the structure of current technologies, those that you constantly interact with or at least may encounter in everyday life.

Resistive touch screen

Resistive touch screens were invented back in 1970 and have changed little since then.
In displays with such sensors, there is a pair of additional layers. However, I’ll make a reservation that the matrix is ​​not at all necessary here. The first resistive touch devices were not screens at all.

The bottom sensor layer consists of a glass base and is called the resistive layer. A transparent metal coating is applied to it that transmits current well, for example, from a semiconductor such as indium tin oxide. The top layer of the touchscreen, with which the user interacts by pressing the screen, is made of a flexible and elastic membrane. It is called the conductive layer. An air gap is left in the space between the layers, or it is evenly dotted with microscopic insulating particles. Along the edges, four, five or eight electrodes are connected to the sensor layer, connecting it with sensors and a microcontroller. The more electrodes, the higher the sensitivity of the resistive touchscreen, since changes in voltage across them are constantly monitored.

The touchscreen controller detects voltage changes and reads readings from the electrodes. Four, five, eight meanings and all different. Based on the difference in readings between the right and left electrodes, the microcontroller will calculate the X-coordinate of the press, and based on the differences in voltage on the upper and lower electrodes, it will determine the Y-coordinate and thus tell the computer the point at which the layers of the touch screen layer touched.

Resistive touch screens have a long list of disadvantages. So, they are, in principle, unable to recognize two simultaneous presses, not to mention more. They don't do well in the cold. Due to the need for a layer between the sensor layers, the matrices of such screens noticeably lose brightness and contrast, tend to glare in the sun, and generally look noticeably worse. However, where image quality is of secondary importance, they continue to be used due to their resistance to stains, their ability to be used with gloves and, most importantly, their low cost.

Such input means are widely installed in inexpensive mass devices, such as information terminals in public places and are still found in aging gadgets such as cheap MP3 players.

Infrared touch screen

The next, much less common, but nevertheless relevant option for a touch screen is an infrared touchscreen. It has nothing in common with a resistive sensor, although it performs similar functions.

The infrared touchscreen is constructed from arrays of LEDs and photosensitive photocells located on opposite sides of the screen. LEDs illuminate the surface of the screen with invisible infrared light, forming something like a spider's web or coordinate grid on it. This reminds burglar alarm, as it is shown in spy action films or computer games.

When something touches the screen, whether it's a finger, a gloved hand, a stylus, or a pencil, two or more beams are interrupted. Photocells record this event, the touchscreen controller finds out which of them are not receiving enough infrared light and, based on their position, calculates the area of ​​the screen in which an obstacle has arisen. The rest is to match the touch with what interface element is on the screen at that location - the software's job.

Today, infrared touch screens can be found in those gadgets whose screens have a non-standard design, where adding additional touch layers is technically difficult or impractical - in e-books based on E-link displays, for example, Amazon Kindle Touch and Sony Ebook. In addition, devices with similar sensors, due to their simplicity and maintainability, attracted the attention of the military.

Capacitive touch screen

If in resistive touch screens the computer registers the change in conductivity that follows a press on the screen directly between the layers of the sensor, then capacitive sensors record the touch directly.

The human body and skin are good conductors of electricity and have an electrical charge. You usually notice this by walking on a wool carpet or taking off your favorite sweater and then touching something metal. We are all familiar with static electricity, have experienced its effects ourselves and have seen tiny sparks flying off our fingers in the dark. A weaker, imperceptible exchange of electrons between the human body and various conductive surfaces occurs constantly and this is what capacitive screens record.

The first such touchscreens were called surface capacitive and were a logical development of resistive sensors. In them, only one conductive layer, similar to the one used previously, was installed directly on top of the screen. Sensitive electrodes were also attached to it, this time in the corners touchpad. Sensors monitoring the voltage on the electrodes and their software were made noticeably more sensitive and could now detect the slightest changes in the flow electric current across the screen. When a finger (another conductive object, such as a stylus) touches the surface with a surface capacitive touchscreen, the conductive layer immediately begins to exchange electrons with it, and the microcontroller notices this.

The advent of surface capacitive touchscreens was a breakthrough, but due to the fact that the conductive layer applied directly on top of the glass was easily damaged, they were not suitable for the new generation of devices.

The top layer of this type of touchscreen screen has a protective function and can be made from tempered glass, for example, the famous Gorilla Glass. Below are the thinnest electrodes that form a grid. At first they were placed on top of each other in two layers, then to reduce the thickness of the screen they began to be placed on the same level.

Made from semiconductor materials, including the aforementioned indium tin oxide, these conductive hairs create an electrostatic field where they intersect.

Because the electrode array is made quite small and dense, such a system is able to track touch very accurately and can easily pick up multiple touches at once. In addition, the absence of additional layers and interlayers in the sandwich of the matrix, sensor and protective glass has a positive effect on image quality. True, for the same reason broken screens, as a rule, are replaced completely. Once put together, the projected capacitive touch screen is extremely difficult to repair.

Now the advantages of projected capacitive touchscreens do not sound like something amazing, but at the moment iPhone presentations they ensured the technology a colossal success, despite the objective disadvantages - sensitivity to dirt and humidity.

Pressure-sensitive touch screens - 3D Touch

The ideological predecessor of pressure-sensitive touch screens was the proprietary Apple technology, called Force Touch, used in smart watch company, MacBook, MackBook Pro and Magic Trackpad 2.

Having tested interface solutions and various scenarios for using pressure recognition on these devices, Apple started implementation of a similar solution in their smartphones. In the iPhone 6s and 6s Plus, pressure recognition and measurement became one of the touchscreen functions and received the commercial name 3D Touch.

In order to teach the capacitive touch screen to recognize clicks and distinguish between several degrees of pressure, engineers from Cupertino needed to rebuild the touch screen sandwich. They made changes to its individual parts and added another one to the capacitive one, new layer. And, interestingly, in doing this, they were clearly inspired by outdated resistive screens.

This development could have been the end of the material about touch screens, if not for another technology that was predicted to have a great future several years ago.

Wave touch screens

Surprisingly, they don't use electricity and don't even have anything to do with light. Surface Acoustic Wave system technology uses surface acoustic waves propagating along the surface of the screen to detect the point of touch. The ultrasound generated by the piezoelectric elements at the corners is too high to be detected by human hearing. It spreads back and forth, bouncing off the edges of the screen multiple times. The sound is analyzed for anomalies caused by objects touching the screen.

Wave touch screens have few disadvantages. They begin to make mistakes after the glass is heavily soiled and in conditions loud noise, but at the same time, in screens with such a sensor there are no additional layers that increase the thickness and affect the image quality. All sensor components are hidden under the display frame. In addition, wave sensors allow you to accurately calculate the area of ​​contact between the screen and a finger or other object and, based on this area, indirectly calculate the force of pressing the screen.

We are unlikely to encounter this technology in smartphones due to the current fashion for frameless displays, but several years ago Samsung experimented with the Surface Acoustic Wave system in monoblocks, and as components for slot machines and advertising terminals, panels with acoustic touchscreens are still sold

Instead of a conclusion

1

The structure of the touch screen (touchscreen) and problems associated with its replacement

Touch screen- an information input and output device, which is a screen that responds to touches.

Resistive touch screen


The resistive touch screen consists of a glass panel and a flexible plastic membrane. A resistive coating is applied to both the panel and the membrane. The space between the glass and the membrane is filled with micro-insulators, which are evenly distributed over the active area of ​​the screen and reliably isolate conductive surfaces. When the screen is pressed, the panel and membrane are closed, and the controller, using an analog-to-digital converter, registers the change in resistance and converts it into touch coordinates (X and Y).


In general terms, the reading algorithm is as follows:
1. A voltage of +5V is applied to the upper electrode, the lower one is grounded. The left and right are short-circuited and the voltage on them is checked. This voltage corresponds to the Y-coordinate of the screen.
2. Similarly, +5V and ground are applied to the left and right electrodes, and the X-coordinate is read from the top and bottom.

Capacitive touch screens

A capacitive (or surface capacitive) screen takes advantage of the fact that an object large capacity conducts alternating current.

A capacitive touch screen is a glass panel coated with a transparent resistive material (usually an alloy of indium oxide and tin oxide). Electrodes located at the corners of the screen apply a small alternating voltage (the same for all corners) to the conductive layer. When you touch the screen with your finger or other conductive object, current leaks. Moreover, the closer the finger is to the electrode, the lower the screen resistance, which means the greater the current. The current in all four corners is recorded by sensors and transmitted to the controller, which calculates the coordinates of the touch point.

In earlier models of capacitive screens, D.C.- this simplified the design, but if the user had poor contact with the ground, it led to failures.
Capacitive touchscreens are reliable, about 200 million clicks (about 6 and a half years of clicks every second), do not leak liquids, and tolerate non-conductive contaminants very well. Transparency at 90%. However, the conductive coating is still vulnerable. That's why capacitive screens widely used in machines installed in secured premises. They do not respond to a gloved hand.

Multi-touch(English multi-touch) is a function of touch input systems that simultaneously determines the coordinates of two or more touch points. Multitouch can be used, for example, to zoom an image: as the distance between the touch points increases, the image enlarges. In addition, multi-touch screens allow multiple users to operate the device simultaneously. They are often used to implement other, more simple functions touch displays such as single touch or quasi multi-touch.
Multitouch allows you to not only determine the relative position of several touch points at any given time, it determines a pair of coordinates for each touch point, regardless of their position relative to each other and the boundaries of the touch panel. Correct recognition of all touch points increases the capabilities of the touch input system interface. The range of tasks solved when using the multi-touch function depends on the speed, efficiency and intuitiveness of its use.

The most common multi-touch gestures

Move your fingers - smaller
Spread your fingers - get bigger
Move multiple fingers - scroll
Two Finger Rotate - Rotate an object/image/video

Problems with resistive touch screen installation

Sometimes a complete analogue of the required wheelbarrow is not at hand, or the pinout of the cable is different, the following problems may arise:
1.Touch rotated 90.270 degrees
- Swap X-Y



2.The touchpad is turned horizontally
- Swap X+ , X-


3. Turn the touch upside down
- Swap Y+, Y-


These solutions need to be implemented if the problem does not go away after calibrating the touch screen.

Replacing the touch screen did not help.
- Reflash the phone

Resistance at TOUCHSCREEN contacts
Y-,Y+=550 Om Without pressing
X-,X+=350 Om Without pressing

Y+,X+=from 0.5 to 1.35 kOm Measurements were taken in different corners of the touchscreen when pressed. Without touching the touchscreen, the resistance is infinity.
Y-,X- = from 1.35 to 0.5 kOm Measurements were taken in different corners of the touchscreen when pressed. Without touching the touchscreen, the resistance is infinity.

IN different models On touch screens, resistance may fluctuate. These measurements were taken on the touch screen from the I9+++ phone.

When is it time to replace your touchscreen?

It's time to replace the touch screen in the following cases:
- if he does not respond to touch
- you found an “oily stain” on it (multi-colored stains)
- it is impossible to calibrate the touch screen
- after entering the message and selecting the English text input mode, try to put dots over the entire area, if lines appear instead of dots, then it’s time to change
- after entering the service-miscellaneous-Touch Screen, try to put dots over the entire area; if green stripes appear instead of crosses, it’s time to change
- if you try to click on an icon, desktops flip through or icons fall off (vertical shedding of icons in iPhone-like phones)
- if 5 minutes after calibration you again do not hit the icon you click on