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Active Sensor – Definition & Examples

Active Sensor – Definition & Examples


An Active Sensor is a kind of sensor or transducer that emits or generates energy or signals to collect data about its surroundings. Additionally, the data collected by remote sensing is used for anything from cartography to resource exploration to atmospheric & chemical measurements.

Relatively, remote sensing is also vital to the Internet of Things (IoT). This is where almost any physical or logical object can be armed with a unique identifier & the ability to transfer data over a network unconventionally.

Application for Active Sensor:

Generally, active sensors are broadly in use in several fields & applications, such as radar, lidar, sonar, ultrasound, laser, and microwave.


It is an active radio detection and ranging sensor that provides its source of electromagnetic energy. Whether airborne or spaceborne, an active radar sensor emits microwave radiation from an antenna in a sequence of pulses.

Lidar (light amplification stimulated emission of radiation):

This is a light detection & ranging sensor that uses laser radar to transmit a pulse & a receiver with sensitive detectors to measure the echoed light.

Sound Navigation and Ranging (Sonar):

It is a technology that utilizes sound waves to identify and locate objects underwater.


This employs ultrasonic waves that can penetrate through solid or liquid materials and produce images or measurements of the internal structure or condition.


It is a device that emits highly focused and coherent beams of light (laser light) to measure distances, detect objects, or gather data.


a microwave refers to electromagnetic radiation with wavelengths in the microwave frequency range.

Key Characteristics of Active Sensor:

Here are a few key characteristics of active sensors:

  • Signal Emission: Active sensors release some form of energy or signal, such as electromagnetic waves (radar, lidar), sound waves (sonar), or other types of signals (infrared beams).
  • Measure Response: Once emitting the signal, the sensor measures the response or reflection of that signal from objects or substances in its environment.
  • Distance Measurement: Active sensors are usually used for distance or proximity measurement. For example, radar & lidar sensors emit electromagnetic waves & measure the time it takes for the waves to ricochet from an object to calculate its distance.
  • Applications: Active sensors have an extensive range of applications, including automotive safety systems (collision avoidance), robotics, navigation (GPS), environmental monitoring, and more.
  • Energy Source: Active sensors usually require a power source to generate and emit the signal, which can be electricity (as in radar or lidar), batteries (portable sensors), or other energy sources.
  • Accuracy & Precision: Active sensors often provide high accuracy & precision in measurements as they control the emitted signal and can measure its characteristics upon return.

Advantages of Active sensor:

  1. Weather-free: Artificial microwave radiation can penetrate clouds, light rain, and snow.
  2. Sunlight-free: can be operated day & night.
  3. Radar breaches vegetation and soil: can gain information about surface layer from mm to m depth.
  4. It obtains information about the moisture content of the soil layer.
  5. Various applications: Usage of active sensors varies in oceanography, hydrology, geology, glaciology, agriculture, and forestry services.

Disadvantages of Active Sensor:

  1. The pulse power is primarily low and can be influenced or interfered with by other radiation sources.
  2. A radar signal doesn’t contain any spectral characteristics.
  3. Complex analysis, cost-intensive.


In conclusion, Active sensors are resourceful tools that emit signals to gather valuable data across various applications. They provide accurate and controlled measurements, making navigation, object detection, and environmental monitoring invaluable.

Relatively, their ability to operate independently of external factors ensures reliability in diverse environments. However, active sensors often require a continuous power source, affecting their energy efficiency and contributing to higher costs.

Additionally, they also raise privacy concerns in some applications. When utilized thoughtfully and with attention to safety, active sensors are essential for modern technology, enhancing our ability to interact and understand the world.

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