• Sourcing sensors allow current to flow out from the V+ supply.
• Sinking sensors allow current to flow in to the V- supply.
• Photo-optical sensors can use reflected beams (retroreflective), an emitter and detector (opposed mode) and reflected light (diffuse) to detect a part.
• Capacitive sensors can detect metals and other materials.
• Inductive sensors can detect metals.
• Hall effect and reed switches can detect magnets.
• Ultrasonic sensors use sound waves to detect parts up to meters away.