Location and verification of the proximity sensor Xiaomi Redmi Note 9

Xiaomi’s current smartphones, including the popular Redmi Note 9, feature a sophisticated sensor system that provides a comfortable interaction with the device. One key element of this system is the proximity sensor, which automatically turns off the screen when you hold the gadget to your ear during a phone call. Understanding where this component is located is critical for users who are faced with problems with sticking screens or improper call performance.

Owners often wonder about the physical location of the sensor, because the Redmi Note 9 used hidden technology. Unlike older models, where you could see a distinctive black window above the screen, here the sensor is hidden under the display or in the thinnest gap of the case, which creates certain difficulties in diagnosis, especially if the screen is glued to a thick protective film or glass that blocks infrared radiation.

The malfunction of this node can turn smartphone use into torture: people hear you but you can’t hear them, or the screen lights up with their cheeks to reset a call. In the Redmi Note 9, the sensor is integrated directly into the top of the display module hidden under the protective glass. In this article, we will discuss in detail the anatomy of the device, methods of software verification and ways to fix typical hardware failures.

Design and hidden location of the sensor

The Proximity Sensor technology in the Xiaomi Redmi Note 9 is implemented using an infrared emitter and receiver. The uniqueness of the design is that the sensor does not have a separate notch in the upper frame. Engineers placed the sensor under the display layer in the upper central part, which allowed to increase the usable area of the screen and make the design more holistic.

This solution, known as the Virtual Proximity Sensor, requires high calibration accuracy in the factory, and it passes through the screen array, making it sensitive to any foreign object in the vicinity of the top of the case, and even a microscopic layer of glue from poor-quality protective glass can cause false positives.

⚠️ Attention: Use of cheap protective glasses with a black frame covering the upper central part of the screen is guaranteed to lead to inoperability of the proximity sensor.

Physically, the sensor is a miniature module soldered to the display plume or placed on a separate board under the screen. Accessing it in the case of hardware repairs requires a complete disassembly of the device and dismantling of the display module, which is a complex procedure that requires special equipment and skills.

How to check the performance of the sensor

Before you take a device into a service or disassemble it, you need to run a software diagnostic, and the MIUI shell on which the Redmi Note 9 is based has a powerful engineering menu built in to test all the components, which is the first step to determine whether the problem is software or hardware.

There is a universal code that works on most Xiaomi devices to enter the testing mode. You do not need third-party applications, since the system tools provide the most accurate data on the state of iron. The verification process takes no more than a minute and requires no special knowledge.

• 📱 Open the phone app and enter the secret code ##6484## to log into the engineering menu. CIT.
• 🔍 In the list that appears, find the item "Proximity sensor" or "approximation sensor" and click on it.
• ✋ Close the top of the screen with your palm and remove it: the values should change from 5.0 (far) to 0.0 (close).

If the values change correctly, but problems persist in normal calls, it is likely that a third-party application or setting conflict is to blame. If there is no response to closing the hand at all, or the value of "stuck" on one digit, this indicates a physical malfunction or a critical calibration error.

Calibration of the sensor through the engineering menu

Often, the sensor is physically functional but its software thresholds are knocked down, in which case calibration can return the device to normal operation. The procedure is simple, but requires care: during the setup, there should be no foreign objects on the screen, including fingers or dust.

To start calibration, go back to the main menu. CIT-So, if you do the test, select "Proximity sensor." You'll see a green "Calibration" button on the screen. Make sure you keep your phone upright and the front panel is completely clean before you press. Any obstacle in the upper part of the screen will cause the reference values to be incorrectly recorded.

When the button is pressed, the system automatically records new sensitivity parameters, and when the process is successfully completed, it is accompanied by vibration and an audible signal, and if the calibration fails, the system will issue a notification, often indicating that the sensor needs to be cleaned or the module replaced.

Typical causes of failures and their elimination

The most common cause of sensor problems on the Redmi Note 9 is the use of non-original accessories: protective glasses with a wide black frame or a thick layer of glue block the infrared beam, and the cause can be trivial contamination of the upper part of the body with fat or dirt, which are invisible to the eye, but block the sensor.

Another common problem is software failure after the MIUI update. In newer versions of firmware, the sensor algorithms can change, leading to conflicts with the old calibration settings, in which case it helps to reset the settings to factory or recalibrate through the engineering menu.

• 🧼 Carefully wipe the top of the screen with a microfiber, paying attention to the area above the speaker.
• 🛑 Remove the protective glass or film to exclude their effect on the operation of the IR emitter.
• 🔄 Reset the sensor settings through the menu CIT or a complete reset of the device.

⚠️ Note: If you use a case with high sides, make sure it doesn’t hang over the top edge of the screen, creating a shadow for the sensor.

In rare cases, the problem is that the display plume is unsticked inside the body after falling. The impact can cause the module to micro-shift, which stops the sensor from "seeing" through the screen. Diagnostics require disassembly, so if simple methods have not worked, it is worth consulting a specialist.

Alternative screen control methods

If the proximity sensor on the Xiaomi Redmi Note 9 finally fails, and the screen replacement is not planned, you can use software crutches. There are special applications and settings that allow you to ignore the sensor readings or replace its function with other control methods.

One effective way to do this is to use Hold to Answer or voice control, so you can set the phone so that it doesn't respond to your face, but only shuts down the screen at the touch of the power button, which is less convenient, but it makes it comfortable to make calls without the ever-burning screen at your cheek.

Also in the developer settings or through third-party utilities (for example, "Proximity Sensor") Reset/Fix") You can try to force the sensor driver to restart without restarting the system completely, which helps in situations where the sensor "hangs" after calling through the messenger.

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Try to disable “Enhanced Call Mode” in call settings – sometimes this feature conflicts with the sensor on older versions of MIUI.

When hardware repairs are needed

There are a number of signs that the software methods are powerless and require intervention in the iron. If after removing the protective glass, cleaning and calibration, the sensor continues to show a value of 0.0 (as if the object is always nearby), most likely, the problem is physical.

Often the plume itself that connects the sensor to the motherboard fails, especially if the phone has been hit or moisture hit. In the Redmi Note 9, the sensor can be part of the display module, and its replacement is only possible with the screen, which greatly increases the cost of repair.

Contact the service center is necessary if:

• 🔨 The phone fell down the screen, after which the display stopped fading.
• 💧 The device was in contact with water, even for a short time.
• 📉 Calibration in the engineering menu is constantly terminated by the error "Fail".

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If the software calibration three times in a row gives an error, further attempts are pointless - you need to replace the display module or repair the plume.

Frequently Asked Questions (FAQ)