New Miniature Proximity Sensors

Pepperl+Fuchs' family of miniature 3- and 4-mm diameter inductive proximity sensors are now available with a smooth or threaded barrel and deliver a sensing range up to 1.0 mm. Their small size and longer sensing range make them suited for use in applications that require detection of small and narrow metal targets that are otherwise difficult to detect with larger body sensors.

"In applications like semiconductor and electronics machinery, grippers, counting and sorting, and other applications that are implemented in a compact machine environment, detecting metallic targets smaller than 3 mm can be a significant challenge," says David Rubinski, product manager for Pepperl+Fuchs. "The new miniature proximity sensor fits into our family of small sensors and provides an industry standard 3-mm diameter solution that can detect smaller targets."

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

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

Designers need to match an application with small targets to a sensor that can detect the smaller target size. The user can specify a larger sensor with longer sensing range, but it might not reliably see the target. Because of the energy in the coil system, it's important for engineers to match the sensor to the application and the target size they are detecting.

"The goal is overall reliability and getting accurate, consistent readings," Rubinski says. "We have a 3-mm sensor that offers a smooth barrel and a 4-mm sensor with a threaded barrel for applications where it is an advantage to thread the sensor into the equipment."

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

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

In designing the new unit, the focus of the development effort was extending the .6-mm sensing range.

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

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