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Automotive semiconductors and sensors from Bosch

MEMS accelerometer

What is a MEMS accelerometer?

A MEMS accelerometer is a microelectromechanical systems device that measures acceleration by detecting the displacement of a movable proof mass suspended within a micromachined structure. The device converts mechanical motion into electrical signals through capacitive, piezoresistive, or piezoelectric sensing mechanisms fabricated on silicon substrates. MEMS accelerometers can measure static acceleration (such as gravity) and dynamic acceleration (such as vibration or motion) across one, two, or three orthogonal axes.

How do MEMS accelerometers compare to piezoelectric accelerometers?

MEMS accelerometers and piezoelectric accelerometers represent two distinct sensing approaches for acceleration measurement, with different fabrication methods and performance characteristics.

Attribute
MEMS Accelerometers
Piezoelectric Accelerometer
Attribute
DC Response
MEMS Accelerometers
Measures static and dynamic acceleration
Piezoelectric Accelerometer
Dynamic acceleration only (AC-coupled)
Attribute
Size
MEMS Accelerometers
Millimeter-scale packages
Piezoelectric Accelerometer
Larger discrete sensors
Attribute
Integration
MEMS Accelerometers
On-chip signal conditioning
Piezoelectric Accelerometer
External conditioning circuits required
Attribute
Temperature Range
MEMS Accelerometers
-40°C to +125°C (automotive grade)
Piezoelectric Accelerometer
-50°C to +150°C (industrial grade)

MEMS accelerometers excel in applications requiring DC acceleration measurement, such as tilt sensing, crash detection or gravity detection, while piezoelectric devices traditionally offer superior performance for very high bandwidth and high-frequency vibration analysis. The silicon micromachining process enables MEMS devices to integrate analog-to-digital conversion and digital signal processing on the same chip, reducing system complexity.

How does Bosch participate in the MEMS accelerometer market?

Bosch develops and manufactures MEMS accelerometers for automotive applications in its own semiconductor fabs and pioneered key MEMS manufacturing technologies, including the Bosch process (DRIE), with manufacturing sites specializing in advanced silicon micromachining. The company’s accelerometer portfolio includes single-axis and multi-axis devices designed for automotive temperature ranges and qualification standards such as AEC-Q100.

The accelerometers from Bosch integrate into vehicle systems for airbag deployment, stability control, navigation applications, active suspension, road noise cancellation, condition monitoring, headlight levelling and inclination measurement.

Bosch’s position as both an automotive system supplier and MEMS device manufacturer enables integration of accelerometers with other inertial sensors and electronic control units within complete vehicle systems.

Frequently Asked Questions

What is a MEMS accelerometer?

A MEMS accelerometer is a micromachined sensor that measures acceleration by detecting the displacement of a suspended proof mass within a silicon structure. The device converts mechanical motion into electrical signals through integrated sensing elements fabricated using semiconductor processes.

What does an accelerometer measure?

Accelerometers measure acceleration forces in units of g-force (multiples of Earth’s gravitational acceleration). They detect both static acceleration, such as the constant downward pull of gravity for tilt measurement, and dynamic acceleration from motion, vibration, or impact events.

How is acceleration detected physically?

A movable proof mass suspended by flexible beams deflects when subjected to acceleration forces. Capacitive sensing electrodes detect changes in spacing as the proof mass moves, converting mechanical displacement into measurable electrical signal variations that correspond to applied acceleration.

Where is it used in vehicles?

Vehicle accelerometers enable airbag deployment systems, electronic stability control, rollover detection, and hill start assist functions. They monitor longitudinal acceleration during braking and acceleration events, lateral acceleration during cornering, and vertical acceleration for suspension control and impact detection.

What limits accuracy?

Temperature variations affect the mechanical properties of silicon structures and electronic components, introducing measurement drift. Noise from vibration, electromagnetic interference, and manufacturing variations in the micromachined structures can degrade precision, particularly at low acceleration levels near the sensor’s resolution threshold.

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