The SICK WTB11-2P2431 is a photoelectric proximity sensor with background suppression from the W11-2 series, using a visible red LED light source. It detects objects up to 350 mm away, with a minimum sensing distance of 20 mm, and ignores background surfaces beyond that set point — so it won't false-trigger on a conveyor belt or machine frame behind the target. Output is PNP, switching at 100 mA load current, with a 2.5 ms response time. You can set it for light-on or dark-on operation. Power it from 10 to 30 VDC, and it'll run from -30 °C up to 60 °C ambient. The housing is sealed to IP66, IP67, and IP69K — that last one means it survives high-pressure, high-temperature washdown cycles common in food processing and beverage lines. The M12 4-pin connector makes for quick swap-out without opening the panel gland.
At 15.6 mm wide and 48.5 mm tall, this sensor fits into tight machine frames where a wider barrel-style sensor won't go. Mounting brackets for the W11-2 series are standard; the M12 connector exits the back, so plan for about 30 mm of clearance behind the sensor for the mating cable.