Photoelectric Sensors: Advantages and Disadvantages

This page explores the pros and cons of photoelectric sensors. We’ll define what they are and then delve into their advantages and disadvantages.

Definition of Photoelectric Sensor:

A photoelectric sensor converts light into an electrical signal, or vice versa. It typically uses a transmitter (like a light-emitting element) and a receiver (a light-detecting element).

There are several types of photoelectric sensors, each with its own construction and applications: reflective, thrubeam, and retroreflective.

Image alt: Light Sensor

Let’s briefly describe each type:

• Reflective or Diffuse Photoelectric Sensor: The transmitter and receiver are housed together. The transmitter emits light, and the receiver detects the light reflected from the target object.
• Thrubeam Photoelectric Sensor: The transmitter (Tx) and receiver (Rx) are separate. The target is detected when it interrupts the light beam between the transmitter and receiver.
• Retroreflective Photoelectric Sensor: The transmitter and receiver are in the same housing, and a reflector is placed in the sensor’s line of sight. The light is continuously transmitted and received after being reflected. An object is detected when it interrupts the light path, reducing the amount of reflected light received.

Photoelectric sensors (or light sensors) find use in various applications such as material handling, packaging, and parts detection.

Advantages of Photoelectric Sensors

Here’s a breakdown of the advantages:

• Material Versatility: They can sense all kinds of materials.
• Long Lifespan: Photoelectric sensors generally have a longer operational life.
• Reliable with Long Sensing Range: They offer a long sensing range and are considered very reliable.
• Fast Response Time: They boast a very quick response time.
• Cost-Effective: They’re often less expensive compared to other sensing technologies.
• Small Object Detection (Diffuse): Diffuse photoelectric sensors can detect very small objects, including color marks and labels.
• Transparent Object Detection (Retro-reflective): Retro-reflective types are capable of detecting transparent objects.
• Long Range & Dirty Environment Tolerance (Thru-beam): Thru-beam types excel at long-range detection and are more tolerant of dirty or dusty environments.

Disadvantages of Photoelectric Sensors

Now, let’s consider the drawbacks:

• Lens Contamination: Over time, the lens can become contaminated, affecting performance.
• Sensitivity to Target Properties: The sensing range can be affected by the color and reflectivity of the target object.
• Installation Complexity (Thru-beam & Retroreflective): Thru-beam types require the transmitter and receiver to be at separate locations. Retroreflective types need a reflector in addition to the transmitter/receiver, which can make system installation more complex.