New Miniature Proximity Sensors

Pepperl+Fuchs'family of miniature 3- and 4-mm diameter inductive proximity sensors are nowavailable with a smooth or threaded barrel and deliver a sensing range up to1.0 mm. Their small size and longer sensing range make them suited for use inapplications that require detection of small and narrow metal targets that areotherwise difficult to detect with larger body sensors.

"In applications like semiconductorand electronics machinery, grippers, counting and sorting, and otherapplications that are implemented in a compact machine environment, detectingmetallic targets smaller than 3 mm can be a significant challenge," says DavidRubinski, product manager for Pepperl+Fuchs. "The new miniature proximitysensor fits into our family of small sensors and provides an industry standard3-mm diameter solution that can detect smaller targets."

The new sensor offers a longer sensingdistance than previous units which only had a 0.6 mm range. It's designed forsmall equipment where the targets, geometries and the machine components arevery small and there isn't a need for a lot of distance. The longer 1-mm sensingrange provides flexibility because the sensing face doesn't need to be coupled asclosely to the target material.

Rubinski says that for applications withsmall targets, users also generally need a smaller diameter sensor because,even though larger sensors will have larger sensing distance, they are not thebest for tiny targets.

Designers need to match an application withsmall targets to a sensor that can detect the smaller target size. The user canspecify a larger sensor with longer sensing range, but it might not reliably seethe target. Because of the energy in the coil system, it's important forengineers to match the sensor to the application and the target size they aredetecting.

"The goal is overall reliability and gettingaccurate, consistent readings," Rubinski says. "We have a 3-mm sensor thatoffers a smooth barrel and a 4-mm sensor with a threaded barrel forapplications where it is an advantage to thread the sensor into the equipment."

Another issue to consider is the targetmaterial type because these sensors are generally designed to detect mild steel.Because the sensing ranges are so short in distance, material selection is an importantfactor in getting the proper range because if the application requirement is sensinga non-ferrous type material such as aluminum, the maximum sensing distancingcould be much smaller.

Generally target applications for the miniature proximity sensors are smaller, densely packedequipment where size is a critical constraint on applying the sensor.

Indesigning the new unit, the focus of the development effort was extending the .6-mmsensing range.

That unit is still used in applications wherea longer sensing range is not required. Another application would be a slidetable where the tolerances are tight, so there are very small inaccuracies in thetargeting position because the sensor is right up against the sensing face. Thedesign of the machine guarantees that the tolerances are precise.

The new proximity sensors offer anall-stainless-steel housing, LED indication and a 2-m PUR cable. They alsoprovide three-wire, 10-30V dc connectivity, have a maximum switching frequencyof 1,300 Hz, and are available with normally open NPN or PNP outputs.

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