The Proximity Switch is a popular device for non-contact detection. The Inductive Type, in particular, is widely used and is able to detect metal objects near the detection surface through electromagnetic waves. This proximity switch has the following features:

Specifications:

Voltage: DC 6-36V
Output Current: 300mA
Wiring: Three wires
Polarity: PNP
Dimensions: M18 x 10 x 55mm
Detection Distance: 4mm
Output Status: Normally Open
Part Number: LM18-3008PA
Detection Objects: Conductors.