Tire pressure monitoring systems (TPMS) are available as indirect and direct systems.
Direct systems: There is a tire pressure sensor on each wheel with direct contact to the air of the tire. Values such as air pressure and temperature are determined in real time and transmitted to a vehicle control unit. The accuracy is less than 0.1 bar, which means that even slight deviations from the target pressure are detected at an early stage.
Indirect systems: If the tire pressure is too high or too low, the rolling behavior of the tires also changes.
rolling behavior of the tires also changes: For example, the rotational speed increases because the rolling radius of the tire
decreases with decreasing internal pressure. This is detected by the existing speed sensors on the vehicle's four wheels and reported via the vehicle electronics. Indirect systems are generally slower to respond than direct systems and are less accurate.