Retroreflective sensing, 4 m range, NPN output – fit overview
This Omron E3FB-RN112M is a retroreflective photoelectric sensor in the E3FB series, housed in an M18 threaded brass barrel. It detects opaque objects as small as 7 mm diameter at distances from 100 mm to 4 m using a red LED beam and an external reflector (not included). The 0.5 msec response time suits high-speed counting or position sensing on conveyor lines. Output is NPN, selectable Light On or Dark On, sinking up to 100 mA at 10-30V DC. The prewired 2 m bare-wire cable simplifies installation into existing junction boxes or terminal strips; no connector to source or seal. The cylindrical barrel dimensions are standard 18 mm diameter x 44 mm length, fitting common mounting brackets and through-hole setups.
How the key ratings decide fit
The 4 m retroreflective range is the maximum with a standard reflector; actual sensing distance drops when using smaller or less efficient reflectors. Minimum detectable object is 7 mm diameter, so small parts are reliably seen at full range with adequate reflector alignment. The IP67 and IP69K ratings protect against dust ingress and temporary submersion, and high-pressure, high-temperature wash-downs common in food, beverage, and pharmaceutical lines. The brass body resists corrosion from caustic cleaning agents. Operating temperature -13°F to 131°F. Mirror Surface Rejection (MSR,) prevents false detection on highly reflective targets like polished metal, glass, or shrink-wrapped product. Without MSR, a retroreflective sensor may 'see' the shiny object as the reflector and miss it; MSR suppresses that behavior, so it can detect mirror-like items passing through the beam.
Delta with the PNP, M12 sibling – E3FB-RP21
The closest functional sibling is the E3FB-RP21, which shares the same retroreflective sensing method, 4 m range, 0.5 ms response, MSR feature, and M18 brass barrel. The critical difference for a retrofit or alternate-source decision: the RN112M outputs NPN via a prewired bare cable, while the RP21 outputs PNP via a 4-pin M12 quick-disconnect connector. If your PLC or control card expects NPN (sinking) inputs, the RN112M is the correct drop-in; for PNP (sourcing) systems, choose the RP21. The connector type also matters – the RP21 requires a mating M12 cordset, whereas the RN112M's 2 m cable terminates directly in the panel.