Selecting the right safety light curtain sensors (photoelectric barrier) is critical for protecting personnel in industrial automation. Incorrect choices risk compliance gaps or operational failures. This guide distills the core selection criteria verified by international standards and industry practices.
1.Safety Certification: Non-Negotiable
Safety light curtains must comply with international safety standards, which is the primary consideration in selection:
- Type level:
- Type 2: For low-risk scenarios (e.g., assembly lines where false triggers cause minimal harm)
- Type 4 (Essential for high risk): Mandatory for presses, shears, or robots. Features redundant circuits and fault tolerance
- Performance Level (PL) & Safety Integrity Level (SIL)
- PL e (ISO 13849) or SIL 3 (IEC 62061) required for hazardous machinery
- Certifications: Verify CE, UL, IECEx/ATEX (for explosive environments)
Warning: Type 2 curtains are prohibited for SIL 2/PL d applications per EN 61496-1 Ed.
2.Resolution (Beam Spacing): Match Protection Targets
Resolution defines the smallest detectable object. Choose based on body parts at risk:
| Protection Target | Resolution | Application Example |
| Fingers | 10–14mm | Stamping presses, small machinery |
| Hands/Arms | 20–30mm | Injection molding, CNC machines |
| Body/Passage | ≥40mm | Robotic cells, warehouse gates |
Note: Higher resolution ≠ better! Overly fine spacing (e.g., <10mm) increases false triggers from dust or insects
3. Protection Height & Detection Range
- Protection Height: Must exceed the hazard zone height + 10% margin
- Detection Range:
- Short: <3m (compact machines)
- Medium: 3–10m (most industrial setups)
- Long: >10m (logistics, large conveyors)
- Pro Tip: For reflective/glare-prone areas (e.g., welding), use anti-ambient-light models
4.Response Time: Sync with Machine Dynamics
Critical for calculating safety distance:
Safety Distance = Machine Stopping Time × Object Speed + Margin
- Standard: 10–30ms (low-speed equipment)
- High-speed: <10ms (presses, cutters)
5. Environmental Durability
- IP Rating: Minimum IP65 (dust/water jet resistance); IP67 for oil/coolant exposure
- Temperature: Standard: -10°C to +55°C; extended options
- EMC Immunity: Essential near motors/VFDs to prevent false stops
6. Productivity-Enhancing Features
- Silent (shielding) function: Allows temporary shielding of part of the light beam when materials pass through, avoiding unnecessary shutdown.
- Area Blanking: Programmed shielding of fixed areas (such as conveyor belt positions) to adapt to complex working conditions.
- Cascading control: Multiple sets of light curtains are linked (Autonics supports 4 groups of expansion), covering large equipment.
- Real-time diagnosis: The operating status is displayed on LED or 7-segment code for quick fault location.
7. Installation & Maintenance
- Mounting: Adjustable brackets
- Beam Alignment: Laser guides or digital indicators
- Maintaining friendliness: Modular design and clean Windows reduce long-term operation and maintenance costs
Selecting safety light curtains demands precision: verify certifications (Type 4/SIL 3), match resolution to hazards, and validate performance on-site. Never compromise on third-party test reports. Partner with trusted suppliers for compliance and reliability. Remember: Effective safety isn’t purchased—it’s engineered
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