Direct Tyre Pressure Monitoring Systems

摘要

For many years, I thought that Tyre Pressure Monitoring Systems (TPMS) were an unnecessary automotive complication. However, having spent six years driving a car with a factory-fitted TPMS installed, my opinion has changed. Over 50,000 miles, the system alerted me to four slow punctures and two major deflations, all in good time and before the situations posed a safety risk. Although mandatory today, TPMS has been fitted to several popular makes, since the early 2000s. There are two different systems: Direct and Indirect TPMS. As an under-inflated tyre possesses a smaller circumference, Indirect TPMS uses the existing individual wheel speed hardware, which also supplies the car's anti-lock and anti-skid control functions, to identify a pressure drop and alert the driver through either an illuminated fascia light or via an on-dash message. Direct TPMS employs a sensor within each wheel and communicates with a separate transmitter; while more accurate and popular, Direct TPMS is also more costly to repair and demands periodic maintenance.