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Type 4 Safety Light Curtain
Type 4 Safety Light Curtain (SIL3/PLe) — High-Risk Machine Protection
Built for hazardous area protection on high-risk machinery, the ENT line of Type 4 safety light curtains delivers the highest ratings available — Cat.4, PLe, SIL3. Every unit carries TÜV approval to IEC 61496-1,2:2020, with 14 mm–45 mm resolution options and detection distances reaching 70 meters.
Type 4 | Cat.4
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SIL3 | PLe
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TÜV Certified
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IP65
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CE Compliant
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Why High-Risk Machines Need Type 4 Safety Light Curtains
Workplace accidents, injuries and fatalities resulting from unprotected and unguarded machinery are costing U.S. manufacturers alone an estimated $128 billion annually in direct and indirect costs, according to a paper published by Colorado State University. Single point-of-operation machine incidents at high-risk equipment – mechanical and hydraulic presses, robotic cells – can trigger OSHA fines, downtime and ROI loss, and in some cases, worker disability or death.
A Type 4 safety light curtain is a photoelectric electro-sensitive protective device (ESPE). It projects an array of infrared light beams across the danger zone, forming an invisible barrier at the machine access point. Any beam interruption — by a human finger, hand, or torso — triggers the safety circuit, commanding the machine to a complete stop within milliseconds. Unlike Type 2 devices that run periodic self-checks at fixed intervals, Type 4 units perform continuous redundant self-diagnosis with automatic crosschecking. If any internal fault occurs, the system immediately enters a safe error state and shuts down the hazardous motion.
An important factor when considering an environment classified as high-risk under ISO 13849-1:2023 is system capability. Type 4 carries the highest functional safety ratings — Cat.4, PLe, SIL3 — which make it the only compliant solution for machinery where a hazard analysis demands the maximum safety integrity. These light curtains protect personnel from injury at the front and back access points of any factory automation, metalworking, or packaging line setup.
ENT Series Safety Light Curtain — Key Specifications
Safety Level
Type 4, SIL3, PLe
Resolution Options
14 / 25 / 45 mm
Detection Range
Up to 70 m
Response Time
From 6.0 ms
Protection Height
Up to 1,960 mm
Enclosure Rating
IP65
ENT vs. Competing Safety Light Curtain Sensors — Specification Comparison
The ENT series covers all three resolution classes for machine guarding across diverse industrial applications, with each model sharing identical safety architecture, IP65 environmental protection, and optical synchronization technology. No separate safety modules or additional signal cables are needed between the transmitter and receiver — only the optical sync link.
| Parameter | ENT-14 (Finger) | ENT-25 (Hand) | ENT-45 (Body) |
|---|---|---|---|
| Optical Axis Spacing | 10 mm | 20 mm | 40 mm |
| Detection Accuracy | 14 mm | 25 mm | 45 mm |
| Detection Distance | A: 0–10 m | B: 0–16 m | C: 0–5 m | D: 0–40 m | E: 0–70 m | ||
| Protection Height | Up to 1,960 mm (configurable by beam count) | ||
| Response Time | 6.0–30.8 ms (scales with beam count) | ||
| Safety Rating | Type 4, Cat.4, PLe, SIL3 | ||
| Standards | IEC 61496-1,2:2020 | EN 61508-1~4:2020 | ISO 13849-1:2023 | ||
| Protection Rating | IP65 | ||
| Supply Voltage | 24 VDC ±20% | ||
| Safety Output | Dual PNP or NPN transistor (≤100 mA per channel) | ||
| Cross-Section | 34 × 28 mm | ||
| Connection | M12 connector | ||
| Configuration | Infrared one-button PNP/NPN switching | ||
Protection Height & Beam Count Calculator
Enter your machine opening dimensions to get beam count, protection height, response time, and unit length.
Every ENT unit features per-segment indicator lights that display operational status for individual beam zones — showing whether each zone is clear, blocked, or misaligned — so technicians can detect alignment issues immediately without additional diagnostic hardware. An infrared-based optical configuration system eliminates DIP switches and proprietary software, cutting commissioning time to under one hour.
Selection Guide: Which ENT Model for Your Application
| Application | Recommended Model | Resolution | Detection Distance | Mounting Note |
|---|---|---|---|---|
| Mechanical press point-of-operation | ENT-14 | 14 mm (finger) | A: 0–10 m | Perpendicular to access |
| Hydraulic press side guarding | ENT-25 | 25 mm (hand) | B: 0–16 m | + Safety relay module |
| Press brake operator zone | ENT-14 | 14 mm (finger) | C: 0–5 m | Near-distance mode |
| Robotic cell entry point | ENT-45 | 45 mm (body) | D: 0–40 m | Cascading configuration |
| Palletizing line passage | ENT-45 + muting | 45 mm (body) | E: 0–70 m | + Reflective column |
For protective applications involving multiple access points, cascading software allows cross-point interconnection between multiple light curtains and a single, integrated safety controller. Conventional safety devices use expensive cable runs and junction boxes, while reflectors enable a single transmitter and receiver pair to guard two or three sides of an access point for maximum value.
ENT Model Selector — Find Your Configuration
Answer 3 questions about your machine to get a recommended model, distance class, and accessory list.
ENT vs. Competing Type 4 Light Curtains — Specification Comparison
All Type 4 safety light curtains meet the same IEC 61496 standard. Your decision will depend on resolution levels, detection distances, response times, physical dimensions, and total lifetime costs.
| Specification | QJKH ENT | Brand A | Brand B |
|---|---|---|---|
Performance & Detection |
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| Resolution Options | 14 / 25 / 45 mm | 14 / 30 mm | 20 / 40 mm |
| Max Detection Distance | 70 m | 15 m | 20 m |
| Min Response Time | 6.0 ms | 6.5 ms | 12 ms |
| Price Positioning | Factory-direct competitive | $$$$$ | $$$ |
Hardware & Smart Features |
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| Cross-Section | 34 × 28 mm | 41 × 27 mm | 30 × 30 mm |
| IP Rating & Connector | IP65 (Standard M12) | IP65/IP67 (Proprietary + M12 adapter) | IP65 (Standard M12) |
| PNP/NPN Switching & Indicators | IR one-button / Per-segment LED | Software required / Full-length LED | DIP switch / Status LED only |
| Cascading & Reflective Column | ✓ Adapter-based / ✓ Multi-side guarding | ✓ / — (Not supported) | ✓ / — (Not supported) |
At 70 meters maximum detection distance, the ENT suits large-format applications — palletizing lines, warehouse entry gates, conveyor perimeters — where competing units would require multiple sender-receiver pairs. Its compact 34 × 28 mm cross-section fits tight mounting envelopes, and standard M12 connectors eliminate the proprietary cable lock-in that some OEMs have expressed frustration with.
Get a Custom Comparison →Type 4 Safety Light Curtains
Industrial Workshop Integration & Applications
Resolution Guide: 14 mm Finger | 25 mm Hand | 45 mm Body Detection
Resolution determines how close a safety light curtain can be mounted to the hazard zone. Finer resolution allows a shorter minimum safety distance, but the machine’s stopping performance must be fast enough to halt before a hand or finger reaches the danger point at the designated approach speed.
Safety Distance Calculation (ISO 13855)
This approach distance varies as a function of system response time and device operating speed through the ISO 13855 equation:
S = K × T + C
- S = Minimum safety distance (mm)
- K = Approach speed: 2,000 mm/sec (hand), 1,600 mm/sec (body)
- T = Light curtain response time plus machine stop time
- C = Penetration allowance: 8×(d−14) mm for d ≤ 40 mm; 850 mm for d > 40 mm
Calculation Example: ENT-14 on a Mechanical Press
Configuration: ENT-14 with 32 beams (detecting accuracy d = 14 mm); response time t = 10.2 ms. Machine braking time t = 100 ms.
S = 2,000 × (0.0102 + 0.100) + 8 × (14 − 14) = 2,000 × 0.1102 + 0 = 220.4 mm
At 220 mm from the press opening, the ENT-14 reaches finger-level detection, while allowing the operator to work comfortably in the area. You can also compare this to a competitor unit, with 12 ms response time: this same press would require 244 mm, pushing the curtain even further and reducing the ergonomic reach of the work station. Every millisecond of response time translates to 2 mm of additional safety distance at hand approach speed.
Safety Distance Calculator (ISO 13855)
Enter response time and machine stop time to calculate the minimum mounting distance for your installation.
Safety Light Curtain Sensor Applications: Press Machine, Hydraulic Press & Robotic Cell Protection
Mechanical Press: Point-of-Operation Guarding
Stamping presses represent one of the highest-risk scenarios in metal fabrication. The ENT-14 mounts perpendicular to the press opening at the calculated safety distance, creating a finger-detection barrier across the point of operation. During the press cycle, any beam interruption triggers a safety stop within the 6.0–10.2 ms response time window. A paired SRB-2A1B safety relay module monitors the dual-channel output and manages manual or automatic reset logic.
Hydraulic Press: Multi-Sided Protection
Hydraulic presses fed from multiple sides present a more complex guarding challenge. The ENT cascading system addresses this directly: two or three ENT-25 units interconnect through cascading adapters and are controlled by a single safety controller. Where physical constraints prevent direct mounting on every side, reflective columns redirect the beam plane around corners — guarding two or three access points with a single transmitter-receiver pair.
Robotic Cell Entry Points
Robotic cells require body detection at entry points, combined with muting for automated material handling. The ENT-45 supports muting so that pallets and fixtures can pass through the detection zone without interrupting production, while maintaining full personnel safeguarding at all other times. Dual optical synchronization channels (A and B frequency bands) prevent crosstalk with neighboring safety light curtains on adjacent machines.
Press Brake & Bending Machine
Press brakes are usually required to be positioned as close as possible to their operators in order to preserve reach of the protective envelope. When used in near-distance mode (C: 0-5 meters), the ENT-14 with a response time of just 6.0 milliseconds maintains a safety distance of less than 250 mm.
Machine Guarding Return on Investment
12–24
Month Typical Payback
3–5×
ROI Within 3 Years
$128B
Annual U.S. Injury Cost
$1.4B
Global Market (2025)
Certifications & Compliance: IEC 61496 | ISO 13849 | TÜV Certified
All ENT series light curtains ship with third-party TÜV approval — not self-certification, but independent confirmation that the unit complies with the requirements of international safety standards.
Type 4 — IEC 61496-1,2:2020
Cat.4 — ISO 13849-1:2023
PLe — ISO 13849-1:2023
SIL3 — IEC 61508-1~4:2020
CE — European Conformity
TÜV Certified
IP65 — IEC 60529
GB4584 — China National Standard
IEC 61496 Type 4
IEC 61496 Type 4 represents the most stringent category of electro-sensitive protective devices. Units in this class run continuous self-tests with redundant fault detection — if any internal circuit fails, power is removed within one response cycle. A PL (Performance Level) of e further confirms this is the highest achievable safety integrity for control system components in hazardous area applications.
SIL3 (IEC 61508)
Safety Integrity Level 3 requires a probability of dangerous failure per hour between 10⁻⁸ and 10⁻⁷ — the highest level attainable by safety light curtains.
PLe (ISO 13849)
Performance Level e is the highest reliability category for safety-related control system components, with a mean time to dangerous failure (MTTFd) exceeding 100 years per channel.
Manufacturing & Testing Facility
Our manufacturing site in Hangzhou houses a 5,000 m² electronics facility equipped with SMT high-precision placement lines and MV-6eOMNI 3D AOI inspection. The adjacent 1,000 m² R&D laboratory conducts EMC, temperature cycling, humidity, vibration, shock, and IP ingress testing — all on-site, enabling rapid certification of new product variants. TÜV test reports are available upon request for procurement qualification.
Procurement Guide: Pricing Factors, Lead Time & OEM Support
Safety light curtain pricing depends on resolution, protection height, detection distance class, and order volume. Rather than publishing a fixed price list, we calculate each quote based on the following factors:
Pricing Factors
Resolution class
The 14mm finger detection units command a premium over 45mm body detection owing to higher beam density and narrower optical tolerances.
Height of protection
For a given width, taller curtains need more optical cell pairs thus increasing component cost in proportion to height
Detection distance class
Standard models cover D (40 m) and E (70 m). Long-range applications use the E-class optics with higher-power IR emitters.
Order volume
Volume pricing is available for multi-unit and repeat orders
Accessories
Cascading adaptors, reflective columns, safety relay modules, mounting brackets quoted separately
OEM & Customization
Our core engineering team brings over 20 years of industrial safety sensor development experience. We support OEM labeling, custom protection heights, modified cable lengths, and application-specific firmware configurations. The in-house laboratory enables rapid prototyping and certification of custom variants.
Free Sample Program
We provide complimentary test units to qualified buyers evaluating the ENT series for integration projects. Test the build quality, optical alignment, response time, and environmental resistance under your actual operating conditions before committing to volume orders.
As a factory-direct manufacturer, QJKH eliminates the distributor markup that typically adds 30–50% to the end-user price of Western-brand safety light curtains. Those savings pass directly to you. Contact our application engineering team for a detailed quote based on your configuration and volume.
Contact for Pricing & SamplesType 4 Safety Light Curtain FAQs
Type 4 is the highest safety classification for electro-sensitive protective equipment under IEC 61496. It requires continuous redundant self-monitoring — if any internal component fails, the device immediately enters a safe error state, preventing the machine from operating under compromised protection. Type 4 is required wherever risk assessment identifies serious or fatal injury potential.
Type 2 devices run periodic self-checks at preset intervals — a fault between checks goes undetected. Type 4 devices perform continuous self-diagnosis with redundant crosschecking, so any fault is detected within a single response cycle. For high-risk applications (mechanical presses, hydraulic presses, robotic cells), Type 4 is the minimum requirement per ISO 13849 risk assessment methodology.
Selection is driven by risk assessment and the body part at risk. 14 mm provides finger detection — required at point-of-operation zones on presses where the operator’s hands enter the hazard area. 25 mm covers hand detection for general machine entrance guarding. 45 mm handles body detection at perimeter gates and entry points. Tighter resolution demands closer mounting to the hazard, which shortens the available safety distance and may affect your floor layout. Use our model selector for a guided recommendation.
Use the ISO 13855 formula: S = K × T + C. K is the approach speed (2,000 mm/s for hands, 1,600 mm/s for whole body). T is the total system response time (light curtain response time + machine stopping time). C is the penetration allowance based on resolution. Use our interactive calculator to compute the exact mounting distance for your setup.
Yes. Every ENT series unit is certified to IEC 61496-1,2:2020 by independent TÜV testing, with full test reports on file. Our Hangzhou laboratory conducts EMC, thermal cycling, vibration, shock, and ingress testing to IP65. This is third-party verified certification, not self-declaration.
Muting temporarily suspends the light curtain during an automated cycle — allowing pallets or material to pass through the beam field — then re-enables protection once the muting sensors confirm the object has cleared. Blanking permanently masks one or more specific beams to accommodate a fixed obstruction (such as a fixture or bracket) within the detection zone, without creating unprotected dead zones. Both features are configured without software on the ENT series.
Yes. Qualified buyers receive a complimentary ENT series sample unit for hands-on evaluation. Test the optical alignment, response time, IP65 sealing, and build quality under your actual operating conditions before committing to a volume order. Contact our factory team to arrange shipment.
Yes — custom protection heights, cable lengths, firmware, and OEM labeling are all available. Custom variants go through TÜV certification in our in-house lab.
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