TPMS systems come in two forms—direct (dTPMS) and indirect (iTPMS). Both solutions are used in practice, but there are major differences between them. Direct TPMS is the more technically complex variant. Unlike indirect TPMS, it uses additional sensors. In both cases, the systems indicate a loss of pressure by means of a warning message or a symbol (tire with an exclamation mark) in the cockpit.
How does direct TPMS (dTPMS) work?
In a direct TPMS, each tyre is equipped with a sensor in the valve or on the rim. These sensors measure tyre pressure and temperature and send the data by radio to a control unit in the vehicle. The system immediately detects when the pressure falls below a specified threshold (for example, 20 per cent below the recommended pressure).
Direct TPMS have the advantage of measuring tyre pressure very accurately and in real time. In addition, dTPMS also detects pressure loss when the vehicle is stationary. The disadvantages include the cost of the sensors and their maintenance. The battery in the sensors must be replaced after a few years. In addition, the sensors can be damaged when changing tyres.
How does indirect TPMS (iTPMS) work?
Indirect TPMS does not use a special pressure sensor in the tyre. Instead, the existing ABS/ESP sensors are used to monitor the wheel speed. When air is lost, the tyre becomes smaller and rotates faster. The iTPMS detects the difference.
Indirect TPMS has the advantage of being less expensive than TPMS. After all, no additional sensors are required. There are alsonomaintenance costs.
However, iTPMS is not as accurate and does not detect uniform pressure loss across all four tyres. Furthermore, it only works while the vehicle is in motion.
What is an integrated TPMS?
Regardless of the sensors, tyre pressure monitoring systems can also be divided into integrated and non-integrated TPMS. Integrated TPMS are connected to a telematics system so that the air pressure values can be displayed not only in the vehicle, but also at fleet management and dispatch.
A prerequisite for an integrated TPMS is the connection of a telematics solution via the vehicle’s Controller Area Network (CAN). CAN is a standardised bus system that enables real-time communication between different vehicle components. Telematics solutions such as FleetVision from AddSecure use CAN bus integration to transmit and analyse vehicle data, including tyre pressure.
Conclusion: Integrated direct TPMS are the best solution
Integrated direct TPMS systems exploit the full potential of modern tyre pressure monitoring systems. Integrated TPMS systems provide decision-makers in the company with important information on which to base their decisions and offer the greatest possible benefits. They enable centralised monitoring of all vehicles in real time. In the event of pressure loss, not only the drivers but also the dispatchers or fleet management are warned immediately. This prevents consequential errors such as tyre blowouts or accidents. Automated maintenance tickets to support workshop planning and historical analyses over any period of time are also possible.