Many users, when they first encounter screens of modern smartphones, often confuse the terminology, asking where the motion sensor on the Xiaomi Redmi Note 9 is located. In fact, in the classical sense of an accelerometer or gyroscope that responds to the physical movement of a device in space, there is no separate visible element. The screen rotation and tilt response are provided by a complex of internal sensors built directly into the motherboard or combined into a single IMU module.
However, if by motion sensor you mean a sensor that turns off the screen while you're talking or locks the phone in your pocket, it's a proximity sensor, which is the one that most often raises questions, because Xiaomi has used virtual technology in the Redmi Note 9, abandoning a physical hole in the top bezel, a decision driven by the desire to increase the usable area of the display and create a symmetrical design of the front panel.
Understanding how this system works is critical to the proper operation of the gadget. The Redmi Note 9 uses virtual proximity sensor technology based on the analysis of light reflection from the surface of the screen. This means that you will not physically find a separate eye under the glass, as in the old models, the sensor is tied to software algorithms and a special layer under the display, which sometimes leads to false positives that require manual calibration.
Hardware implementation of the sensor in Redmi Note 9
The technical performance of the front part of the Redmi Note 9 is significantly different from the predecessors of the Note series. Xiaomi engineers integrated the emitter and receiver of infrared light directly under the matrix. IPS-Visually, at the top of the screen, next to the front camera, you can see a subtle blackout or a specific pattern that hides the working elements of the sensor. The absence of a physical cutout allows you to achieve high tightness and protection from dust, but imposes certain requirements for operation.
The principle is to emit an invisible infrared beam and analyze its reflection from objects held to the phone. When you hold your smartphone to your ear during a call, the distance to the object is reduced, and the sensor detects the change in the intensity of the reflected signal. Based on this data, the MIUI operating system decides to turn off the touchscreen and quench the image to prevent accidental cheek pressing.
It is important to note that due to the location under the display, the sensitivity of such a sensor can vary depending on the thickness of the protective glass or film. Cheap protective films with an opaque frame can block the area of operation of the sensor, causing constant problems with locking the screen. Therefore, when choosing accessories for the Redmi Note 9, it is recommended to give preference to products with a cutout under the top or completely transparent options that do not have blackouts in the speaker area.
⚠️ Attention: Using thick protective glasses with a black frame at the top can completely block the virtual sensor, which will lead to the inability to complete the call in the usual way.
For a deeper understanding of the differences between sensor types, consider the Characteristics Comparison Table:
| Characteristics | Physical sensor | Virtual Sensor (Redmi Note 9) |
|---|---|---|
| Location. | Separate hole in the frame | Under the display layer |
| Sensitivity | Tall, stable. | Depends on the calibration and film |
| Dust protection | Requires additional membranes | Complete leakproofness |
| Accessories' influence | Minimum | High (depending on transparency) |
Software management and engineering menu
Because it is impossible to physically influence the location of the sensor, the main work of setting up is through the software interface. In Xiaomi smartphones, including the Redmi Note 9, there is a hidden section of the engineering menu designed to diagnose and calibrate equipment, accessed through the standard Phone application, which allows users to conduct tests without installing third-party software.
To get into the test menu, you need to type a special code. Type ##6484## on the dial keyboard. Immediately after entering the last digit, the CIT menu will open. This is a complete list of all the device modules. We are interested in a item that can be called "Proximity Sensor" or "Proximity Sensor".
Inside this section, you'll see the current sensor readings. In the normal state, when nothing is closing the top of the screen, the value should be 5.0 (or close to 5). If you close the top of the screen with your palm, the value should change to 0.0. If the values do not change or jump randomly, this is a direct signal that you need to calibrate or there is a hardware malfunction.
The calibration process in the engineering menu is usually automated. Once you enter the sensor test, an instruction appears on the screen: "Place your hand over the top of the phone and then remove it." Follow the instructions: cover the top of the hand, remove your hand, and press the "Pass" or "Calibrate" button. The system will record the new sensitivity thresholds in the device's memory.
Typical problems and their diagnosis
Despite the cleverness of the system, Redmi Note 9 users often face a situation where the screen does not go out during a conversation or, conversely, goes out immediately after the call begins. This can be extremely annoying, especially during long conversations, most often due to a software driver failure or contamination of the upper part of the screen.
The first step in diagnosis should always be to clean the surface. Fat spots, dust or water droplets in the top third of the display can distort the readings of the infrared sensor. Wipe the screen with a soft microfiber cloth. If the problem persists, it is worth checking whether you have any applications that conflict with the call management system, such as third-party "bells" or number detectors.
☑️ Sensor diagnostics
Also worth noting is the behavior of the smartphone in the case. Some cases have protruding sides that can partially overlap the area of operation of the virtual sensor. Remove the case and check the sensor again. If without the case everything works correctly, then the problem is in the accessory, and it is better to replace it with a model with a more accurate fit for the Redmi Note 9.
⚠️ Note: If calibration through the engineering menu does not help, and the sensor values do not change when closing the screen with your hand, the display plume or the sensor module itself may be damaged, which requires contacting the service.
Setting Sensitivity Through Applications
When standard MIUI methods fail, specialized tools from the Google Play Store come to the rescue, applications like Proximity Sensor Reset/Fix or Proximity Calibration allow for deeper calibration, which is restricted to the standard interface, and force the sensor configuration files to be overwritten.
Before you start calibration, make sure you are in a room with normal lighting and there is no protective film on the screen if you plan to remove it in the future. The process usually takes no more than a minute: the application will ask you to close the sensor, then open, and repeat the cycle several times to average the values.
After successful calibration with third-party software, be sure to restart your smartphone. The reboot is necessary for the Android operating system to reread the new values of the sense thresholds!