ST_Sensing Technologies

There are primarily three fundamental categories of sensor technologies: Proximity, Motion and Force sensor technologies

Proximity Sensors

Proximity sensors are non-contact sensors that detect the presence of an object without any physical contact. Data collected from the environment is converted into an electrical signal that can be measured. Under this category, there are Inductive, Capacitive and photoelectric sensors.

1. Inductive Sensors

Figure 1: Proximity Sensors

Generates a high-frequency electromagnetic field. When a metallic object enters this field, eddy currents are induced in the object, which absorb energy and reduce the sensor's oscillation amplitude. This change in amplitude triggers the sensor's output.

How it Works: Detects only metallic objects. Highly reliable and resistant to dust and dirt. Common in industrial automation for detecting parts on assembly lines, controlling machinery, and counting metal items.

 2. Capacitive Sensors

Figure 2: Capacitive Proximity Sensor

Uses a built-in electric field. The sensor and the object act as two plates of a capacitor. When an object enters the field, it changes the capacitance between the sensor and the object. This change is detected and triggers an output.

How it works: Detects both metallic and non-metallic objects (e.g., liquids, powders, plastics, wood) because any material with a dielectric constant greater than air will affect the capacitance. Used for liquid level sensing, detecting material in hoppers, and controlling packaging processes.

3. Photoelectric Sensors

Figure 3: Types of Photoelectric Sensors

How it works: Uses a beam of light (often infrared) to detect objects. A light emitter and a receiver work together. An object is detected when it either interrupts the light beam or reflects it back to the sensor.

Advantages

• It has a longer detection range than inductive or capacitive sensors. 
• Photoelectric Sensors detect a wide range of materials and are suitable for high-speed applications like sorting and counting items on conveyor belts.

4. Ultrasonic Sensors

Figure 4: Ultrasonic Sensor

Emits high-frequency sound waves. The sensor measures the time it takes for the sound wave to bounce off an object and return. This "time of flight" measurement determines the object's presence and distance.

How it works: Emits high-frequency sound waves. The sensor measures the time it takes for the sound wave to bounce off an object and return. This "time of flight" measurement determines the object's presence and distance. Used in parking sensors, liquid level measurement, and robotics for collision avoidance.

Advantages

• Unaffected by the color or transparency of an object. 
• Works well in dusty or misty environments.