The Prosense Basic series of proximity sensors offer great value for general industrial applications. These round inductive proximity sensors made from nickel-plated brass are offered in barrel sizes from 8mm to 30mm. Flush and non-flush mount styles are available in sensing distances up to 15mm and offer an LCP (liquid crystal polymer) active face.
PNP logic models are available with either a N.O. or N.C. output; NPN logic is also available with a N.O. output. M12 quick-disconnect or 2m pigtail termination styles are available for all sizes. These IP67-rated sensors start at $9.75 and have a lifetime warranty.