User's Manual

Reifendruck-Kontrollsystem
Tire pressure monitoring system
Seite 2 von 4
Figure 2: schematic representation of the system´s layout in a vehicle
2.1 Electronic wheel unit
The battery-based electronic wheel units are mounted inside the tires to measure the tire pressure
and the temperature of the electronic wheel systems. Every electronic wheel unit
has an individual code (ID), which is transmitted with every message. Furthermore, the data telegram
includes information about the remaining service life of the battery.
The measured data are transmitted from the wheel through a transmission point.
A tire pressure monitoring system has to carry out two main functions: The recognition of a pressure
loss and the measurement of the absolute pressure.
For the measurement of the absolute pressure, a relatively low frequency of measurement data
transmissions is sufficient, a pressure loss must be transmitted immediately. The electronic wheel
system shifts automatically to the various operating modi in order to carry out these functions at a
minimum power consumption.
Transmitting intervals
• Normally, every electronic wheel unit measures the tire pressure and the approximate
temperature of the air in the tire every three seconds but if the measured values are stable, sending
processes are carried out only every 54 seconds.
• At a pressure loss of more than 0.2 bar per minute, the electronic wheel unit shifts temporarily to
a high transmission frequency. It will then carry out measurements and sending processes every
0.8 seconds. This energy management allows battery-based operation with a sufficient service life.