Basic Principles and Evolution

Photoelectric sensors have been utilized in automation for over 60 years. These sensors detect visible or invisible light and respond to changes in light intensity, providing manufacturers with essential operational data, such as component location confirmation and product counting. Advancements in electronic miniaturization have led to more compact, easier-to-mount sensors that are often available at lower costs.

Challenges and Innovations

Detecting Clear Liquids

In the bottling industry, verifying liquid presence and level can be challenging, especially with clear bottles and water. Traditional sensors struggle with low-contrast targets. However, the use of a 1,450 nm infrared sensing beam has proven effective. Water absorbs about 1,000 times more energy at this wavelength than at visible wavelengths, creating a high-contrast application and enabling accurate detection.

High Excess Gain Applications

In detecting contents within colored or frosted containers, a photoelectric sensor requires sufficient excess gain to avoid signal attenuation from contaminants or the container itself. Balancing excess gain ensures that the sensing beam can penetrate the container but is absorbed by the liquid, preventing false positives or negatives.

Long-Range and Small Object Detection

Detecting small flanges on moving objects at a distance can be difficult due to manufacturing constraints. Fixed-field sensors with a visible red laser sensing beam offer a solution. These sensors detect objects within a defined sensing field, ignoring those beyond the cutoff. Their background suppression feature, narrow beam, and visible laser make them ideal for small object detection at a distance.

Durability and Environmental Resistance

Photoelectric sensors must withstand harsh industrial environments, including water, chemicals, extreme temperatures, and contaminants. Sealing and IP ratings (IP67, 68, 69K) play a crucial role in preventing moisture ingress. Additionally, sensors with a liquid-tight PFA outer shell offer resistance to acids and harsh cleaning chemicals. For high-temperature applications, remote sensors using glass fiber optics and remote amplifiers ensure reliability.

Overcoming Environmental Challenges

Even sensors with high IP ratings can be affected by dust, smoke, fog, and oil buildup. Sensors with high excess gain can overcome these challenges by burning through contaminants to reliably detect the target. Opposed-mode sensors are particularly effective in these applications.

Luminescence Sensors

For detecting clear materials or identifying them on other surfaces, luminescence sensors use UV light to detect luminophores, which emit visible light when excited. These sensors are useful in applications like lumber optimization, detecting tamper-evident seals, and fluorescent product markings.