Answer

1. What is Ultrasonic Sensor?

Non-contact distance/proximity sensor using ultrasound (40kHz) time-of-flight.

2. How It Works

Transmitter emits chirp → reflects off object → receiver measures TOF $T$, distance $d = c\cdot T/2$, $c≈343$m/s air.

3. Types

Type	Principle
Transceiver (single)	Same element TX/RX
Separate TX/RX	Two elements
Analog	Continuous $d$ voltage
Digital	Threshold binary

4. Advantages

• Works on any material/color, transparent.
• Range 2cm–4m, low cost.
• Not affected by light.

5. Disadvantages

• Slow (sound speed), 40ms per measurement.
• Beam spread (30°), poor for narrow.
• Temperature affects $c$, soft materials absorb.
• Minimum dead zone ~2cm.

6. Applications

• Robot obstacle avoidance, parking.
• Level sensing (tank).
• Medical imaging, non-destructive testing.

Final Answer

Ultrasonic = $d=cT/2$ TOF, types transceiver/separate, advantages material-independent range, used for robot navigation and level sensing but slow and beam-wide.