What is the tire pressure monitoring function

[WapCar] Tire pressure monitoring is the real-time automatic monitoring of the tire pressure during the driving process of the car, and alarms for tire leaks and low air pressure to ensure driving safety. There are two common types: direct and indirect.

Direct tire pressure monitoring device

Direct tire pressure monitoring device uses the pressure sensor installed in each tire to directly measure the tire pressure, and uses the wireless transmitter to send the tire pressure information from the inside of the tire to the system on the central receiver module, and then the tire pressure data of each tire is displayed. When the tire pressure is too low or leaks, the system will automatically alarm.

The advantage of the direct tire pressure monitoring system is that: pressure sensor and transmitter are installed on each wheel, if any tire pressure is lower than 25% of the cold tire pressure recommended in the driver's manual, the driver will be warmed.  The warm signal is more accurate, and if the tire is punctured and the tire pressure drops rapidly, the direct tire pressure monitoring system also can give an immediate warming.

In addition, even if the tire slowly venting, the direct tire pressure monitoring system also can be sensed through the trip computer, allowing the driver to directly view the current four tire pressure number from the driver's seat, thereby the driver can know the real tire pressure of the four wheels in real time.

Indirect tire pressure monitoring device

Indirect tire pressure monitoring device, when the tire pressure of one tire decreases, the weight of the vehivle will make the wheel's rolling radius smaller, causing its rotating speed is faster than other wheels. In this way you can compare the speed difference between tires to acheive the purpose of monitoring tire pressure. The indirect tire alarm system actually monitors the air pressure by calculating the tire rolling radius.

The cost of the indirect tire pressure monitoring device is much lower than the direct type, it actually uses the speed sensor on the vehicle ABS brake system to compare the number of rotations of four tires. If one of the tires has low tire pressure, the number of rotations of this tire will be different from that of other tires. In this way, using the same sensors and sensing signals of the ABS system, as long as the in-vehicle computer makes adjustments in the software, new functions can be established in the trip computer to warn the driver that one tire has a lower tire pressure than the other three.

Vehicles using indirect tire pressure monitoring devices will have two problems. One is that most models using indirect tire pressure monitoring devices cannot specifically indicate which tire has insufficient tire pressure. Secondly, if the tire pressures of the four tires are falling at the same time, then this device will also fail, and this situation is generally particularly obvious in the winter when the temperature drops. In addition, when the car is driving through a bend, the number of rotations of the outer wheel will be greater than the number of rotations of the inner wheel, or the tire will slip on sandy or icy roads, and the number of rotations of a specific tire will be particularly high. Therefore, this monitoring method for calculating tire pressure has certain limitations.