Optical Sensors Selection

The most common optical sensor options are photoelectric—diffuse, reflective, and through beam. Laser sensors and fiber-optic sensing units also fall under the optical sensor category.

Photoelectric sensors are mostly presence sensors. Photoelectric sensors detect an object via reflected light or an interrupted beam of light. These sensors are among the most applied sensors in manufacturing due to low cost, versatility, and reliability.

Diffuse photoelectric sensors do not require a reflector. They are used for sensing the presence of nearby objects and are inexpensive sensors.

Through beam offers the longest sensing range and is installed at two points with an emitter unit and receiver unit. Garage door safety sensors are through beam sensors. Presence is indicated when the beam is interrupted. A fork light sensor is an interesting through-beam variant; it has an emitter and receiver in one compact unit. Fork light sensors are used for sensing the presence and absence of small parts.

Reflective photoelectric sensors have a sensor and a reflector and are used for mid-distance presence sensing. For accuracy and cost, they sit midway between diffuse and through beam.

Fiber-optic sensing units are used for presence and distance sensing. Parameters on these versatile sensors can be adjusted to detect various colors, backgrounds, and distance ranges.

Laser sensors are used for long distance presence sensing and are the most accurate in short distance measurement applications.

Vision sensors can be used for bar code reading, counting, shape verification, and more. Vision sensors are a cost-effective use of vision where camera systems would be too costly and complex. Vision sensor bar code reading can be used for tracking individual components and applying the processes identified for that component. The sensor can verify the number of features present on a part. A vision sensor can ascertain if a specified curve or other shape has been achieved. Since these sensors are dealing with light, it is vital to test the sensor in as close to the operating environment in terms of ambient light and background reflectivity as possible. In most applications, it is recommended to place the vision sensor in an enclosure to isolate it from external sources of light. It is a good idea to enlist the aid of a vision sensor manufacturer in sensor testing. Ensure the right fieldbus is specified.

The signal converter changes the analog output signal from a sensor into switching points on the signal converter, another option is to convert to IO-Link process data.


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