Answer

1. What is Accelerometer?

Sensor measuring linear acceleration (m/s²) including gravity, via inertia. Output = acceleration vector.

2. How It Works

Proof mass $m$ suspended by spring. Acceleration $a$ → force $F=ma$ displaces mass $x=F/k$ → displacement → transduction.

• Capacitive MEMS: Movable plate between fixed plates, $C=\epsilon A/d$, $d$ changes with $a$.
• Piezoresistive: Strain gauge on cantilever.
• Piezoelectric: Charge on crystal.

3. Types

Type	Principle	Range
Capacitive MEMS	$C$ change	±2g to ±16g
Piezoresistive	$R$ change	High-g shock
Piezoelectric	$Q$	Vibration only
Thermal	Convection	Low-g

4. Advantages

• Measures tilt (gravity component) + vibration.
• Small MEMS, low power.
• 3-axis available.

5. Disadvantages

• Measures $a+g$ → needs fusion to get orientation.
• Drift, noise, temperature sensitive.
• Cannot measure constant velocity.

6. Applications

• IMU for robot/drone stabilization.
• Tilt sensing, fall detection.
• Vibration monitoring, impact detection.
• Smartphone auto-rotate, step counting.

Final Answer

Accelerometer = proof-mass inertia sensor $F=ma$ → $C/R/Q$ change; types MEMS capacitive/piezoresistive; advantages tilt+vibration sensing, used in IMU and motion tracking.