Pepperl+Fuchs 183811 Photoelectric Sensor

(Model: RL31-54/73c/136)

Type: Retroreflective photoelectric sensor with polarization filter

Polarization filter design enables detection of transparent films & PET bottles and suppresses false triggering from highly reflective surfaces.

Core Specifications

Part No.: 183811, Model: RL31-54/73c/136

Sensing range: 20 ~ 9000 mm (9 m), max. limit 12 m; matched reflector: C110-2

Light source: Modulated red light (630 nm) with polarization filter

Supply voltage: 10 … 30 V DC, no-load current ≤20 mA

Output: 2 push-pull (4-in-1) outputs, dark-on (Q2), max. load 100 mA; short-circuit & reverse polarity protection

Response time: ≤1 ms, max. switching frequency 500 Hz

Protection class: IP67

Connector: M12 4-pin plug

Dimensions: 18 (W) × 62 (H) × 35 (D) mm, plastic housing, net weight 24 g

Ambient temperature: -30 ~ +55 ℃

MTTFd: 920 years

📌 M12 Pin Assignment (EN60947-5-2)

1 BN (Brown): +UB Power Positive

2 WH (White): Q1 (Light-on Output)

3 BU (Blue): 0V GND

4 BK (Black): Q2 (Dark-on Output)

💡 LED Indicators

Green LED: Power supply ON

Yellow LED: Signal status (steady / flashing / off indicates signal reserve)

📋 Application & Features

Ideal for transparent object detection (plastic films, glass bottles, packaging)

Standard RL31 compact housing, widely used on conveyor & packaging machinery

Fixed-parameter version without sensitivity adjustment potentiometer

Application Cases for Pepperl+Fuchs 183811 (RL31-54/73c/136)

Core precondition: Polarized retroreflective, 9 m max range, IP67, dual push-pull output, no adjustment knob, suppress specular reflection & reliably detect transparent objects; factory reflector C110-2 required

Case 1: Beverage PET Bottle Filling Line (Classic Application)

Working condition: High-speed bottle conveyor with highly reflective empty/full transparent PET bottles; standard retroreflective sensors suffer frequent false triggering

Mounting: Sensor on one side, C110-2 reflector opposite; beam crosses the bottle path, distance 3~6 m

Functions: Bottle presence detection, missing bottle alarm, filling machine interlock & counting. Polarization filter eliminates specular reflection from bottle bodies; beam interruption reliably detects transparent PET without missed detection.

Advantages: No on-site calibration required; M12 quick connector; IP67 resistant to splashing water.

Case 2: Horizontal Form-Fill-Seal Packaging Machine (Transparent Packaging Film Detection)

Working condition: High-speed BOPP transparent heat-seal film with unstable reflection causing flickering & signal loss

Mounting: Beam spans the machine frame; film runs between sensor and reflector, distance 2~5 m

Functions: Film break protection & material presence detection to prevent empty sealing & knife damage. Polarization suppresses mirror reflection from thin transparent films.

Note: Signal margin may be insufficient for ultra-thin films (<10 μm); better suited for thicker frosted transparent materials.

Case 3: Logistics Sorting & Roller Conveyor Long-distance Material Detection

Working condition: Long belt/roller lines with cartons & pallets, sensing distance up to 7~9 m, dusty environment

Mounting: Sensor at one end of the passage, reflector fixed on the opposite frame

Functions: Parcel arrival trigger for barcode scanning, sorting cylinder actuation, jam detection & tail material monitoring. Only the sensor side requires power (reflector is passive), saving wiring compared to through-beam sensors. Dual push-pull outputs provide redundant light-on/dark-on signals for PLC logic.

Case 4: Daily Chemical & Pharmaceutical Packaging Line (Glass Vials & Ampoules)

Working condition: Strong specular reflection from glass bottles causing frequent false signals with ordinary photoelectric sensors

Functions: Missing bottle detection, ejector trigger, part confirmation at sealing stations. Wide temperature range (-30~+55℃) fits cold-chain pharmaceutical packaging lines.

Case 5: Industrial Rapid Roll-Up Door Safety Protection

Working condition: 5~8 m wide door openings on factory overhead doors; prevent door closing from trapping people & vehicles

Mounting: Sensor on one door post, C110-2 reflector on the opposite post; beam runs horizontally across the doorway

Functions: Safety circuit; beam interruption stops door closing and triggers reverse opening. IP67 dust & water resistance suits outdoor & car wash humid environments; polarization avoids false triggering from ground water reflection.

Case 6: Automated Warehouse & Stacker Crane Aisle Protection

Working condition: 4~8 m wide storage aisles with metal rack reflections & heavy dust

Functions: Aisle intrusion detection, over-height cargo inspection, pallet position confirmation. 9 m long range covers most aisle widths; polarization filters out metal rack reflections to reduce unstable signals.

Case 7: Automotive Component Conveyor (Glossy Painted Workpiece Anti-False Trigger)

Working condition: Mirror-finish painted bumpers & sheet metal parts cause permanent false triggering on standard retroreflective sensors

Functions: Part presence & station position confirmation. Polarized lens blocks specular reflected light; only actual beam interruption generates a valid output signal, ideal for glossy workpiece inspection.

📌 On-site Operation Notes (Limitations of this fixed model)

1. No sensitivity potentiometer: Signal margin must be verified during selection; not suitable for materials with highly variable light transmittance.
2. Only use polarized reflector C110-2: Ordinary reflective stickers will render the polarized beam ineffective with no return signal.
3. Not recommended for sustained heavy water mist & oil mist that continuously attenuates the light beam.
4. Q1 = light-on, Q2 = dark-on, flexible for different PLC logic.

Not Recommended Applications

Severe fluttering & wrinkling of ultra-thin transparent films (insufficient signal reserve)

Frequent switching between different transparent materials (no adjustable sensitivity)

Sensing distance exceeding 9 m

Installation Guidelines for Pepperl+Fuchs 183811 (RL31-54/73c/136)

Critical preconditions: Polarized retroreflective, no adjustment knob, mandatory use of C110-2 polarized reflector — these three points are the most common installation pitfalls.

1. Optical Beam & Reflector (Top Priority)
2. Reflector rule: C110-2 only. Standard reflective tape/reflectors cannot be used; polarized light path will fail with no reflected signal. The reflector must be perpendicular to the sensor; do not rotate the reflector 90° (crossed polarization = zero signal).
3. Rated range: 20 mm ~ 9000 mm for reliable operation; do not run continuously at the 12 m absolute limit. Avoid installation below 20 mm; near-range polarized beams tend to malfunction.
4. Beam divergence angle: 3°; light spot expands to ~200 mm at 6 m. Ensure the entire light spot falls fully onto the reflector surface.
5. Keep the beam completely clear; brackets, cables and frame edges must not intrude into the optical path. Transparent targets (PET bottles, film) must fully block the beam, not just partially cut across it.
6. Avoid strong reflective backgrounds (polished stainless steel, glossy paint) directly opposite the sensor; even with polarization, close large mirror surfaces may still cause false triggering.
7. Do not arbitrarily rotate the sensor or reflector; misalignment of polarization axis results in total signal loss.
8. Mechanical Mounting, Brackets & Environmental Protection
9. Housing size: 18×62×35 mm. Recommended original brackets: OMH-RL31-01/02/03/05; fasten with M4 screws with moderate torque to prevent cracking the PMMA optical window.
10. Optical window material: PMMA. Do not scratch with hard objects or clean with strong solvents (acetone, thinner, long-term alcohol soaking). Only use dry lint-free cloth or clean water for cleaning.
11. IP67 rating: Tighten the M12 connector fully with intact sealing rings. Mount the connector downward or sideways to prevent water pooling; this sensor is not submersible and cannot withstand continuous immersion.
12. Ambient temperature: -30℃ ~ +55℃. Keep away from heat sources such as motors, heating rollers and hot air outlets. Fit sun & rain shields for outdoor installation.
13. Ambient light resistance: Max. 50,000 Lux. Prevent direct sunlight or high-power strobe lights shining onto the optical window; strong light reduces signal reserve and causes yellow LED flickering.
14. For vibration-prone conveyors & shakers, use rigid mounting plus vibration-damping gaskets to avoid beam drift.
15. Electrical Wiring & Power Supply (M12 4-pin A-coded)

Pin assignment (EN60947-5-2):

1 BN: DC 10–30V Positive

2 WH: Q1 Light-on Output

3 BU: 0V GND

4 BK: Q2 Dark-on Output

1. Power supply: 10–30V DC SELV/PELV safety voltage. Built-in reverse polarity & short-circuit protection; add a small external fuse as extra protection.
2. Push-pull 4-in-1 outputs with max. 100 mA load. Do not drive solenoid valves directly; use an intermediate relay or PLC input module.
3. Use PUR oil-resistant M12 cables (V1-G/V1-W series). Route cables separately from power lines to minimize EMI; avoid repeated bending right at the connector root.
4. Do not run alongside inverter & servo power cables in the same trunking; high-frequency interference will cause signal fluctuation.
5. Alignment & LED Troubleshooting (No Adjustment Potentiometer!)

No potentiometer or setting buttons; sensitivity cannot be adjusted. Only mechanical alignment can secure sufficient signal reserve, which must be confirmed at the selection stage.

Green LED steady ON: Power normal

Yellow LED steady ON: Adequate signal (≥2× switching reserve, ideal operating state)

Yellow LED flashing: Marginal signal (1~2× switching point). Prone to instability from dust, moisture and vibration. Realign the beam or shorten the distance before commissioning.

Yellow LED OFF: No reflected signal; misaligned beam, wrong reflector or blocked light path.

Commissioning standard: Lock the bracket only after the yellow LED stays steadily ON; never accept flashing status for production.

5. Anti-Crosstalk for Multiple Sensors Installed Side-by-Side

Multiple RL31 sensors with intersecting beams or facing the same reflector will suffer mutual optical interference.

Maintain sufficient spacing between sensors

Stagger beam heights to avoid overlapping optical paths

Install light baffles between optical windows if beam separation is impossible.

6. Key Tips for Transparent Object Detection
7. PET bottles & transparent film must fully block the beam. For films thinner than 10 μm, shorten the sensing distance to increase signal reserve.
8. In dusty, misty & oily environments, beam attenuation accelerates; reserve extra signal margin and regularly clean windows and reflectors.
9. Avoid continuous frost & heavy oil sludge buildup on the optical surface, which will steadily weaken the return signal.
10. High-speed packaging lines: Response time ≤1 ms and 500 Hz switching frequency meet most high-speed applications. Calculate the beam blocking duration to prevent missed detection from ultra-short target passage.
11. Maintenance & Prohibited Operations

Do not replace C110-2 with non-polarized reflectors

Do not grind or scratch the optical window

Do not clean lenses with strong solvents

Do not operate continuously beyond the 9 m rated range

Do not rotate sensor/reflector to cross the polarization axis

Regular inspection: Clean optical surfaces & reflectors, check bracket looseness, reconfirm yellow LED status.

8. Safety Reminder

This sensor is not a PLd/PLe safety light curtain and cannot be directly wired into safety stop circuits despite high MTTFd. When used for roll-up door safety protection, the safety circuit architecture must be evaluated separately.

Pepperl+Fuchs Full List | Polarized Retroreflective Photoelectric Sensors (Model + Part No.)

Note: All listed models are Polarized Retroreflective type, requiring dedicated polarized reflectors. Five series: RL31 / RL28&RL29 / ML100 / OBR / OBG (clear object dedicated). The model you currently use (183811) is marked.

Matched polarized reflectors: C110-2, REF-H50, REF-H60, REF-H85-2 (not interchangeable between series).

1. RL31 Series (9 m range, no adjustment knob, dual push-pull 4-in-1; same series as 183811, mainstream for PET packaging lines)

2. RL28 / RL29 Series (Polarization + foreground suppression; eliminates false triggering from nearby debris; 5~9 m, adjustable sensitivity)

3. ML100 Miniature Polarized Retroreflective (3 m / 5 m, compact square housing, adjustable knob; mass model for general conveyors)

All ML100 retroreflective models come with built-in polarization filters for glossy packaging & aluminum foil detection.

4. OBR New Generation Miniature Polarized Retroreflective (IP69K, IO-Link, wide temperature -40~+60℃; food & washdown lines)

5. OBG Clear-Object Dedicated Polarized Retroreflective (For PET, glass & thin films; dual-mode transparent detection)

Difference from standard polarized sensors: switchable transparent detection mode, optimized for ultra-thin films & glass bottles.

| 426200 | OBG5000-R101-2P1-IO-V31 | 0.02…5000 mm | IO-Link, M12 | IP69K, dedicated transparent object detection |

| 426201 | OBG5000-R101-PPF-IO-V31 | 0.02…5000 mm | IO-Link, PPF high-performance version | High-sensitivity transparent detection |

| 426210 | OBG8000-R200-2EP-IO-V15 | 0.02…8000 mm | IO-Link, M12 | 8 m long-range transparent detection |

Quick Selection Guide (Replacement Options for 183811)

1. Direct drop-in replacement (9 m, no adjustment, M12 connector) → RL31 series (183809 / 183810)
2. Adjustable sensitivity, 9 m polarized range + near-object false trigger suppression → RL29 series
3. Limited installation space, ≤5 m range, budget-friendly with adjustable knob → ML100 series
4. Food washdown environment, IP69K & IO-Link data transmission → OBR6000
5. Mass detection of ultra-thin films & glass bottles to avoid missed detection → OBG clear-object series

General Important Notes for Polarized Models

Polarized retroreflective sensors must use dedicated polarized reflectors; ordinary reflective tape will fail with no signal.

Polarized ≠ clear-object sensor: RL31 polarization works for PET bottles, but select OBG for films thinner than 10 μm.

This list only includes models with built-in polarization filters; standard non-polarized retroreflective sensors are excluded.