Types of Sensors

1. Classified by Measured Property

• Position/Displacement Sensors: Detect presence, position, or distance.
• Force/Pressure Sensors: Measure force, weight, or torque.
• Vision Sensors: Capture images for identification, inspection, etc.
• Temperature Sensors: Measure temperature.
• Flow Sensors: Measure gas/liquid flow rate.
• Level Sensors: Detect liquid level in a tank.

1. Classified by Working Principle

• Photoelectric Sensors: Use light (blocked or reflected by an object).
  • Through-beam: Separate emitter and receiver.
  • Retro-reflective: Emitter and receiver together, detect light from a reflector.
  • Diffuse reflective: Detect light reflected directly from the object.
• Proximity Sensors: Detect nearby objects without contact.
  • Inductive: Detect metals only.
  • Capacitive: Detect both metals and non-metals.
• Fiber Optic Sensors: Use optical fibers to guide light to a small sensing head.
• Magnetic Sensors: Detect magnetic fields.
• Vision Sensors/Industrial Cameras: Core component is an image sensor.
• Encoders: Measure rotational or linear position.
  • Incremental: Measure relative movement.
  • Absolute: Provide a unique position value.

III. Classified by Output Signal

• Digital (Switch) Sensors: Output a simple ON/OFF signal. Most common.
• Analog Sensors: Output a continuous signal for measuring variables.
• Network/Bus Sensors: Output data via fieldbus protocols.

Summary: In automation, the most common sensors are those for detecting position, presence, and vision—they are the “sensory organs” of the equipment.