What is the difference between passive sensors and active sensors?
The main difference between passive and active sensors lies in their power requirements and signal generation:
Passive Sensors: These sensors do not require an external power source to operate. Instead, they detect changes in the environment and generate an output signal by converting the detected energy directly, often using principles like resistance or capacitance changes. Examples include thermocouples, which generate voltage based on temperature changes, and piezoelectric sensors, which produce a charge when under mechanical stress.
Active Sensors: Active sensors require an external power source to operate. They emit energy into the environment and measure the reaction or reflection of that energy to detect changes or measure parameters. Common active sensors include ultrasonic sensors, which send sound waves and detect reflections, and infrared sensors, which emit and receive light to sense nearby objects.
In summary:
- Passive sensors: No external power, respond to environmental changes directly.
- Active sensors: Require external power, actively emit and measure energy for detection.
This difference affects sensor selection based on factors like power availability, sensitivity, and application-specific requirements.