In through-beam photoelectric sensing, also known as opposed mode, the transmitter and emitter are in separate housings. Light emitted from the transmitter is aimed directly at the receiver. When an object breaks the beam of light between the emitter and receiver, the receiver’s output changes state.
Through-beam sensing is the most efficient sensing mode which results in the longest sensing ranges and highest excess gain. This high gain enables through-beam sensors to be reliably used in foggy, dusty and dirty environments.