MEMS Vibe
Measures linear acceleration (and, by integration, vibration spectrum) along one to three axes in the 0–10 kHz band, reporting digital g-units over I²C, SPI, or analog mV/g out.
A polysilicon proof mass is suspended above a substrate on tiny torsion springs. Comb-drive electrodes form differential capacitors with the proof mass; acceleration deflects the mass, unbalancing the capacitor pair. A switched-capacitor amplifier reads the imbalance, a sigma-delta ADC digitises it, and on-chip filters bandpass to the desired frequency. Self-test electrodes electrostatically deflect the mass to verify functionality.
In plain terms
Like a fly trapped in a tiny cantilever spring trampoline — every wobble of the trampoline shifts the fly, and the chip reads how far the fly moved.
Why designers use it
- Industrial machine condition monitoring — detect bearing faults, gear wear, and pump cavitation from vibration spectrum changes weeks before mechanical failure.
- Tilt and orientation in consumer devices — phones, cameras, and gaming controllers all use 3-axis MEMS accelerometers.
- Earthquake detection and structural health — distributed networks of MEMS accelerometers on bridges and tall buildings flag damage after seismic events.
- Low cost (under $1 in volume) and tiny package (sub-2-mm) make MEMS the only choice for high-volume embedded applications.
Best for
- Condition monitoring
- Phones
- Drones
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- Where >10 kHz bandwidth or >50 g range is required — pull a piezoelectric IEPE accelerometer.
- Long-term DC tilt with no calibration drift requirements (over years) — MEMS offset drift accumulates; pull a fluid-filled inclinometer or precision optical tilt.
Common mistakes
- Mounting the IC on a flexible PCB cantilever — the board's own resonance shows up in the spectrum and masks the structure-borne vibration.
- Forgetting that surface-mount reflow can permanently shift offset by ~0.1 g — calibrate post-assembly, not pre.
Where you will find it
- An iPhone 15's STMicroelectronics LSM6DSV3 6-axis IMU reads device orientation and step count: the chip's 16-bit ±16 g output feeds the SoC for screen rotation, while a 0.5 mg/√Hz noise floor lets Apple's Health step counter ignore phone shake during walking.
- A SKF Multilog IMx-8 condition-monitoring node strapped to a paper-mill drive uses a TI IWR6843 MEMS-style accelerometer to read 1–10 kHz vibration: the spectrum's bearing-pass frequency components let the maintenance team schedule the bearing change three weeks before it would have failed.
- A USGS ShakeAlert seismic sensor in California uses an Analog Devices ADXL355 low-noise 3-axis MEMS accelerometer: the chip's 25 µg/√Hz noise floor detects the P-wave seconds before the destructive S-wave arrives, automatically triggering BART trains to stop.
A short history
MEMS vibration sensors often use a capacitive accelerometer, which measures the variation of capacitance between a proof mass and a fixed conductive electrode separated by a small gap as the structure moves. This signal can be processed for vibration time and frequency analysis, helping detect conditions like bearing degradation in motors for predictive maintenance monitoring.