Photoelectric sensors are available in a variety of housing styles and operating modes. Background suppression, diffuse, retroreflective, and thru-beam are some of the most common modes. Each mode has unique benefits. This blog discusses the benefits of using thru-beam mode photoelectric sensors.
Long sensing distances
Thru-beam photoelectric sensors have much longer sensing ranges than sensors utilizing other modes. This long range is possible because thru-beam sensors use separate housings for the receiver and the emitter. The emitter sends out the light and the receiver receives the light. When the light beam is broken, the receiver will no longer receive the light, and the output will be triggered. Pepperl+Fuchs Series 61 photoelectric sensors, utilizing thru-beam mode, have 15x the range as the Series 61 utilizing diffuse mode.
Sensing reflective objects
Thru-beam photoelectric sensors can reliably sense reflective objects, a task where nonpolarized retroreflective sensors can fall short. Retroreflective sensors use a reflector to bounce the light back to the receiver. This allows the light emitter and receiver to be contained in the same housing. When sensing a reflective object, the object itself may reflect light into the receiver. Polarized retroreflective sensors can be used to combat this issue, but thru-beam sensors avoid this issue entirely by having the emitter and the receiver in separate housings.
Accurate parts counting
Thru-beam sensors are the most reliable sensing mode for accurate parts counting. The well-defined beam and precision enable accurate parts counting, as long as the parts are large enough to cover the entire beam. And since the sensor is not impaired by reflective objects or backgrounds, it is highly reliable.
Sensing through smoke, mist, and dust
Thru-beam sensors have high gain, and this gives them the ability to optically “burn through” smoke, mist, and dust, allowing them to be used in dirtier environments. More gain means more reliable performance, and cleaning is required less often. Photoelectric sensors using alternate modes have less gain. If there is not enough gain, then the light may be lost in the smoke, mist, or dust and never reach the receiver. Therefore, most other photoelectric modes are not suitable for dirty environments. If used, they would require more maintenance and regular cleaning.
Sensing through containers
The thru-beam's high gain can be used to burn through clear, translucent, or transparent containers. This technique can be used to detect the contents of a container.
Let's sum it up!
Thru-beam photoelectric sensors are a great choice for long range and high reliability. They are offered in a variety of housing styles and are available with fiber optic cable for high-temperature applications.