Sensor features are another area of concern for OEMs. The trade-off is always cost versus performance. Therefore, it is necessary that engineers are able to distinguish between required technical points and “nice to have” features. Most sensor manufacturers divide sensor families into classes, consisting of low-end and high-end models.

Low-end models are a cost effective solution in most general applications where good optical performance is required. Because cost is essential, low-end models typically have housings made with lower-grade plastics or metals. To keep cost low, features such as indicating LEDs and external adjustments are usually not available or are limited to a single indicator and potentiometer. Optical performance is average, and high-tech features that would add significant costs are normally not offered.

High-end models, on the other hand, are packed with high-performance features tailored more toward specialty applications. Housings include high-grade plastics and metals such as stainless steel and aluminum, and commonly include multiple indicators, automatic push button or remote teach-in, light on/dark on selection, rotating electrical connectors and multiple mounting possibilities. Optically, high-end models have improved sensing characteristics including sharper light spots, laser light sources, high ambient light resistance and automatic cross-talk protection, for better overall performance.

Indicating LEDs found on many low- and high-end models are a basic feature that provides visual information about the sensor’s status. LEDs make it easy to test the functionality of a sensor at the sensor itself. If the green power LED is lit, it can be determined that the sensor is receiving power from the supply or transformer. If the yellow LED is not responding as objects pass by the sensor, further examination may be required to determine if the sensor is misaligned or may have its gain (also called sensitivity) adjusted too low.

Some high-end sensor families have higher intensity LEDs with enhanced functionality that can be very beneficial for identifying problems when they occur in the field. These LEDs serve as a diagnostic tool by showing, for example, if the output is shorted or the light being received is at a level so low that the sensor is having problems reliably detecting the target.

Tamperproof models provide a fixed sensing range. Because a misadjusted sensor could inadequately detect the target or could detect objects beyond the target area, tamperproof models are often used prevent unauthorized adjustments to the sensor. Should a sensor become damaged, tamperproof models facilitate quick field replacement because they don’t need to be adjusted, and less time is spent with setup and installation.

Adjustable range models allow the sensing range to be quickly fine-tuned, often by simply turning a potentiometer. This flexibility potentially allows a single adjustable model sensor to potentially replace several fixed range models.

Here are some general considerations for specifying sensors:
• Know your application and form strategic partnerships - partner with an established sensor provider who offers a depth and breadth of solutions and won’t have to “shoehorn” you into a sensor that is “close enough.”
• Consider sensors that offer multiple outputs from a single device - this can significantly reduce inventory requirements and paperwork.
• When possible, go miniature - smaller sensors easily blend into their surroundings and take up less space, and in most cases offer the same performance and sensing ranges as larger options.
• Strive to utilize sensors with industry-standard housings - this greatly simplifies mounting and replacement, and eliminates getting locked into a single sensor manufacturer.
• Look for sensors with flexible mounting configurations - versatility to mount by a threaded snout or by thru-holes for a surface mount, can simplify mounting and reduce inventory requirements.

Thomas Corbett is Product Manager and Gary Frigyes is Product Marketing Manager at Pepperl+Fuchs in Twinsburg, OH ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).
www.am.pepperl-fuchs.com