Pumped Up

This article focuses on microelectromechanical systems that have been one of the hot topics of the engineering world for years now. Tire-pressure monitoring systems have been available on select passenger vehicles since the late 1990s. Tire-pressure sensor modules contain several components. A MEMS pressure sensor is the key element, but the package may also include a temperature sensor, voltage sensor, accelerometer, microcontroller, radio-frequency circuit, antenna, and battery. Some suppliers of MEMS tire-pressure sensors are seeking to eliminate batteries and power the tire-pressure sensing module by an alternative power source. In the sensor module, packaging must expose the sensor to air pressure and protect the rest of the components. Freescale, for example, protects its sensor with a Teflon filter, which makes sure that only dry air can enter and pressurize the diaphragm.