Whether the application is in the engine, tire, or passenger compartment the appropriate
piezoresistive automotive pressure sensor can deliver cost-effective reliability
and long operational life. To select the right sensor, you need to understand the
functions it performs, the conditions in which it operates, and the design attributes
that make it unique.
Pressure sensor lifetime, reliability and cost
There are three overall key attributes to look for when choosing a pressure sensor:
reliability, lifetime, and cost. The sensor should work 100% of the time. It should
operate reliably for 10–15 years, or 150,000–250,000 miles. Finally, given current
automotive trends, the sensor must be very economical.
Reliability is the result of a number of sensor characteristics. Electrical output,
accuracy, operating environment, and mechanical coupling are important considerations
in choosing an automotive pressure sensor. Perhaps the most important, though, are
stability and repeatability. A sensor's temperature and pressure responses should
be predictable. A supplier can ensure the repeatability of its sensors with several
tests and rigorous qualification routines. Such benchmarking includes cycling temperature
in increments from low to high and vice versa and checking for material degradation
during a high-temperature soak test, further enhanced by applying constant and/or
changing pressure and mechanical stress. Because conventional automotive qualification
standards, such as AEC-Q100, are tailored to qualify CMOS circuits and established
standards for pressure sensor qualification are still missing, a lot of experience
is required to perform such qualification tests.
To some extent, long operational life relies on packaging and assembly, which ironically
often cost more than the actual sensor. The packaging cost, size, and ability to
survive the rigors of the road are critical. Extensive exposure to gasoline and
high pressures makes it imperative that the sensor manufacturer uses the proper
materials and mounting.
As in most mass-production industries, change is the major concern in high-volume
automobile manufacturing. Cost reduction is the reason for most production changes.
Pressure from automobile manufacturers to keep unit prices low poses a challenge
for MEMS sensor suppliers that can affect you, the customer. It can take up to four
years to bring a pressure sensor to market, and you need to be aware that only a
few of the most well-established MEMS suppliers may offer the pressure sensors that
meet your needs. As demand grows, there may be a scarcity of some types of sensors.
For more information contact SMI sales at sales@si-micro.com.