• 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.