SICK AG
SICK W4S-3 Miniature Photoelectric Sensor
SICK's compact workhorse photoelectric sensor family — delivering reliable object detection in through-beam, retroreflective, and proximity-mode configurations with IO-Link integration for Industry 4.0 machine applications.
Overview
The SICK W4S-3 is part of SICK's W4 series of miniature photoelectric sensors — one of the most widely used photoelectric sensor families in industrial automation. Compact enough to mount in tight spaces (the W4 housing measures approximately 34 × 14 × 10 mm), it covers through-beam detection ranges up to 20 m, retroreflective up to 4 m, and proximity (diffuse) detection from 20 mm to 300 mm depending on the target material and surface finish.
The W4S-3 includes an IO-Link port (IO-Link v1.1) in addition to the standard switching output. IO-Link enables bidirectional digital communication between the sensor and an IO-Link master — allowing remote configuration of sensitivity, detection mode, and switching logic, and reading back signal quality, temperature, and operational hours diagnostics that standard discrete I/O cannot provide. In a production environment, IO-Link enables automatic sensor parameter reload after replacement, eliminating time-consuming manual re-teaching.
SICK offers the W4S-3 with red light (650 nm) or infrared (880 nm) emitters. Red light variants are preferred for alignment and for detecting transparent objects or detecting objects with low contrast. Infrared variants are more immune to ambient light interference and are better suited for high-ambient-light environments such as outdoor conveyor applications or operations near fluorescent lighting.
Key Features
- IO-Link for smart diagnostics and parameterisationIO-Link communication provides signal quality (margin), ambient light level, sensor temperature, and operating hours — data that standard discrete I/O cannot transmit. Parameter sets stored in the IO-Link master allow automatic sensor configuration restoration after device replacement without re-teaching.
- Multi-mode in one housingA single W4S-3 housing supports through-beam, retroreflective, and diffuse proximity detection modes via software or teach-button configuration, reducing the number of sensor variants stocked in spare parts inventory and simplifying OEM machine BOM management.
- IP67 with M8 or M12 connectorIP67-rated housing and stainless steel versions survive washdown, coolant spray, and high-humidity environments. Standard M8 4-pin or M12 5-pin connector (for IO-Link) plugs directly into SICK's STE M8 and M12 extension cables and IO-Link masters.
- SICK SensorApp integrationIO-Link-capable W4S-3 sensors integrate with SICK's SensorApp ecosystem for cloud-connected condition monitoring. Signal trend data collected via IO-Link master can be uploaded to the SICK SensorApp via MQTT, enabling predictive maintenance alerts when sensor margin degrades below thresholds.
Technical Specifications
| Operating principle | Through-beam / retroreflective / diffuse proximity (selectable) |
|---|---|
| Sensing range (retro) | Up to 4 m with standard reflector |
| Sensing range (through-beam) | Up to 20 m (WL4-3 emitter/receiver pair) |
| Sensing range (proximity) | 20 to 300 mm (target dependent) |
| Light source | Red LED 650 nm or infrared 880 nm |
| Response time | 3 ms (standard); 1 ms (high-speed variant) |
| Output type | PNP/NPN switching + IO-Link v1.1 |
| Supply voltage | 10–30 V DC |
| Output current | 100 mA max |
| Connector | M8 4-pin (standard); M8 5-pin (IO-Link) |
| Protection class | IP67 (standard); IP69K (stainless steel variant) |
| Housing material | PBT thermoplastic; stainless steel 316L option |
| Operating temp | −25 °C to +60 °C |
| Certifications | CE, UL, cUL, KC, EAC |
Typical Applications
- Conveyor presence detection: Retroreflective mode for part-present detection at accumulation zones and transfer points
- Packaging machine: Through-beam for label detection, perforation count, and box end detection on high-speed lines
- Transparent object detection: Polarised retroreflective mode for detecting clear PET bottles, glass containers, and film
- Robotic end-of-arm tooling: Miniature housing fits inside grippers; IO-Link reports part-present confirmation to robot controller
- Washdown food lines: IP69K stainless variant for CIP environments; NPN output to PLC safe-area digital input
Sources & Further Reading
- SICK AG — W4S-3 Product Data Sheet (8018428)
- IEC 60947-5-2:2019 — Low-voltage switchgear: Proximity switches
- IO-Link Consortium — IO-Link Interface and System Specification V1.1.3
- SICK — IO-Link Application Guide (8016282)