The main function of TPMS is to monitor the air pressure inside the car tire in real time and issue a warning when the air pressure is abnormal to ensure driving safety. TPMS is mainly divided into two types: Direct TPMS and Indirect TPMS, and their working principles are different.
1. Working principle of direct TPMS
Core principle:
Direct TPMS directly measures the air pressure and temperature of the tire through the pressure sensor installed inside the tire, and transmits the data to the vehicle control unit (ECU) through wireless signals. The sensor inside each tire or installed on the valve directly measures the air pressure and temperature inside the tire. The sensor has a built-in micro pressure sensor that can capture the changes in air pressure inside the tire in real time. The measured data is sent to the TPMS control module on the vehicle via a wireless signal (usually a radio frequency signal). The sensor is usually powered by a battery and sends data packets regularly. After receiving the data from each sensor, the control module compares it with the preset safety air pressure threshold. When the air pressure of a certain tire is lower than (or sometimes higher than) the safe range, the system will light up a warning light or display specific information on the dashboard to prompt the driver to check and adjust the tire pressure in time. It can provide real-time and accurate tire pressure data. It can detect the specific status of each tire and provide temperature information to help determine whether there is a leak or other abnormal conditions.
2. Working principle of indirect TPMS
Core principle:
Indirect TPMS indirectly determines tire pressure by monitoring tire speed. When a certain tire is under-inflated, its diameter will decrease, causing the tire speed to increase. Indirect TPMS does not require the installation of a separate tire pressure sensor, but indirectly determines tire pressure through the wheel speed sensor of the vehicle’s anti-lock braking system (ABS) or electronic stability program (ESP). When the tire pressure decreases, the diameter of the tire will change slightly, causing the tire speed to differ from other normal tires. The vehicle’s control module identifies which tire or tires may have insufficient air pressure by comparing the speed data of each tire. For example, if the speed of a certain tire is slightly higher than that of other tires, it may be because the tire pressure is low, resulting in a decrease in tire diameter and an increase in the number of rotations. Once the control module detects an abnormality, it triggers the warning indicator light on the dashboard to prompt the driver to check. It is low-cost because no additional independent sensors are required. It does not directly measure tire pressure, so the accuracy is limited by the accuracy of the vehicle’s wheel speed sensor and algorithm; it is not as sensitive to small changes in tire pressure as intuitive TPMS. It is necessary to calibrate and match the vehicle’s wheel speed data regularly, especially when changing tires, tire wear, or changing tire specifications.
Intuitive TPMS: Directly measure air pressure and temperature through sensors in each tire, transmit data in real time, and monitor tire pressure status more accurately.
Indirect TPMS: Utilizes wheel speed sensor data from the ABS or ESP system to indirectly judge tire pressure status by analyzing the difference in speed of each tire. The system structure is relatively simple but the accuracy is low.
TPMS (Tire Pressure Monitoring ) has many positive effects on car driving?
Mainly reflected in the following aspects: Improve driving safety and timely warning. When the air pressure of a tire is lower than the safety standard, TPMS will immediately issue a warning on the dashboard to remind the driver to check in time to prevent safety accidents such as tire blowout or control failure caused by insufficient tire pressure. Prevent tire overheating. Low tire pressure will increase tire friction, resulting in overheating. TPMS can help monitor temperature changes and prevent other problems caused by overheating. Improve fuel economy and reduce rolling resistance. Appropriate tire pressure can effectively reduce the rolling resistance of tires, making the vehicle more fuel-efficient during driving. If the tire pressure is too low, the vehicle will consume more fuel to overcome the additional resistance. Reduce emissions, by improving fuel efficiency, indirectly help reduce harmful emissions, and play a positive role in environmental protection. Improve handling and comfort, and balance wear. Appropriate tire pressure can ensure uniform force and wear on tires, improve vehicle handling and stability, and make the driving experience smoother. Enhance braking performance. Correct tire pressure helps the vehicle maintain better grip during emergency braking, thereby shortening the braking distance and improving safety. Extend tire life and reduce uneven wear. Maintaining correct tire pressure can avoid uneven wear of tires due to insufficient or excessive air pressure, thereby extending the service life of tires and reducing maintenance and replacement costs. Assisting the vehicle’s overall monitoring system to work with other systems. Modern vehicles usually combine TPMS with other safety systems such as ABS and ESP to provide more comprehensive vehicle status monitoring and protection, further improving overall driving safety.
In short, TPMS can not only promptly warn of potential safety risks by monitoring tire pressure and temperature in real time, but also improve fuel efficiency, enhance handling, and extend tire life, providing drivers with a safer, more economical and comfortable driving experience.
