IEC 61496

What is IEC 61496?

IEC 61496 is the international series of standards that sets the design, construction and test requirements for electro-sensitive protective equipment (ESPE): non-contact safeguards such as light curtains, laser scanners and camera or radar systems that detect the presence of people and make a hazardous machine movement stop. Its full title is Safety of machinery – Electro-sensitive protective equipment, and it is a product standard: it describes what the manufacturer of the protective device must demonstrate. How you apply the device on a machine is covered by other standards, such as ISO 13855 for the safety distance and ISO 13849-1 for the complete safety function. For machine builders and integrators, IEC 61496 is therefore the starting point whenever they select a light curtain or scanner.

🧠 Which parts make up IEC 61496?

The series consists of a general Part 1 plus additional parts for each sensing technology. Part 1 is never used on its own: it is always read together with the part that matches the sensing technology.

In the 2020 editions, requirements common to all technologies were moved from Part 2 to Part 1. Part 2 now only covers what is specific to optical beams, such as the effective aperture angle and reflection tests, and applies to wavelengths between 400 and 1,500 nm. Part 5 on radar targets whole-body detection of adult persons in an industrial environment; applications in which the radar itself moves are excluded. The fourth edition of Part 3 (2025) removes requirements that now sit in Part 1, changes the detection and fault detection requirements for Type 2 scanners and describes the use of a scanner as a trip device as an optional function.

Pressure-sensitive mats are not covered by IEC 61496. They fall under ISO 13856-1, because they respond to contact rather than detecting without contact.

🔐 Which ESPE types does the standard define?

The key concept in IEC 61496 is the type. The type expresses how well the device detects its own faults and how well it withstands disturbances such as reflections, extraneous light and electromagnetic interference. Since the 2012 edition, Part 1 maps each type unambiguously to a Performance Level under ISO 13849-1 and a SIL under IEC 62061.

The narrower aperture angle of Type 4 makes it harder for a beam to reflect around a hand via a shiny surface. A Type 4 certified device does not automatically deliver PL e: the whole chain of sensor, safety relay or safety PLC and actuator must reach the required level. If the risk assessment calls for PL d, you need at least Type 3. Before 2020, light curtains in that situation had to be Type 4, because Part 2 then only defined Type 2 and Type 4.

🔧 What does IEC 61496-1 require?

Part 1 describes the functional, design and environmental requirements that apply to every protective device:

• Detection capability - the smallest test object diameter the device is guaranteed to detect anywhere in the detection zone, for example 14 mm for fingers or 30 mm for hands.
• Response time - the manufacturer must state the maximum time between interruption and switch-off of the outputs; for light curtains this is typically between a few and a few tens of milliseconds.
• Outputs (OSSD) - the output signal switching devices are on most devices two redundant PNP semiconductor outputs at 24 V DC with test pulses, so that short circuits and cross-connections between the channels are detected.
• Immunity - resistance to electromagnetic disturbances, ambient light, temperature, vibration and contamination, demonstrated by testing.
• Fail-safe behaviour - on an internal fault, the device must go to a safe state with the OSSDs switched off.
• Optional functions - Annex A describes functions such as restart interlock, external device monitoring (EDM) and muting.
• Marking and documentation - type, detection capability, response time and connection data must be stated on the product and in the instructions.

🏭 How do you apply an ESPE to IEC 61496 in practice?

Because IEC 61496 only describes the device, its application follows a fixed route. The application standard IEC 62046 gives guidance on the selection, positioning, configuration and commissioning of both ESPE and pressure-sensitive mats.

1. Determine the required level. Derive the required PLr or SIL from the risk assessment under ISO 12100.
2. Choose type and technology. For example, a Type 4 light curtain for hand protection on a press, a Type 3 laser scanner for zone monitoring around a cobot, AGV or AMR, or a safety radar in dusty environments where optics fall short.
3. Choose the detection capability. Finger (14 mm), hand (20–40 mm) or body (multi-beam). This determines the intrusion allowance C in the distance formula.
4. Calculate the safety distance. With ISO 13855: S = K × T + C, where K = 2000 mm/s for hand and arm and C = 8 × (d − 14) for a resolution up to 40 mm. Every extra 10 ms of response time costs 20 mm of distance. This formula comes from ISO 13855:2010; the 2024 edition uses S = K × T + DDS + Z, so record in the technical file which edition you applied.
5. Connect safely. Wire the OSSDs to a safety relay or safety PLC, optionally through a safety protocol such as PROFIsafe or CIP Safety, and implement the stop function in line with IEC 60204-1.
6. Validate and document. Measure the machine’s stopping time, test the detection zone with the test object and record everything in the technical file. Repeat this test periodically.

Worked example (ISO 13855:2010): a light curtain with 30 mm resolution, 15 ms response time and a measured machine stopping time of 185 ms gives T = 0.2 s. S = 2000 × 0.2 + 8 × (30 − 14) = 528 mm. Because that exceeds 500 mm, you may recalculate with K = 1600 mm/s. That gives 448 mm, but the 500 mm lower limit then applies.

📏 How does IEC 61496 relate to other standards and legislation?

In Europe the standard is adopted as EN IEC 61496. A manufacturer that fully applies a harmonised edition benefits from a presumption of conformity with the essential requirements. In practice, manufacturers usually have light curtains and scanners type-examined by a notified body. The machine builder then checks the EU declaration of conformity and the CE marking of the safety component.

❓ Frequently asked questions

What is the difference between Type 2 and Type 4 under IEC 61496?

A Type 2 ESPE detects faults only through a periodic test and is suitable up to PL c or SIL 1. A Type 4 ESPE detects faults within its response time, has a narrower aperture angle of ±2.5° and is suitable up to PL e or SIL 3. Type 4 is therefore the usual choice for presses and robot cells.

Is a laser scanner covered by IEC 61496?

Yes, a safety laser scanner is covered by IEC 61496-3 as an AOPDDR, an opto-electronic protective device that responds to diffuse reflection. Most safety laser scanners are Type 3 and therefore suitable up to PL d or SIL 2. They are widely used for zone monitoring and on mobile robots.

Are safety mats covered by IEC 61496?

No, pressure-sensitive safety mats fall under ISO 13856-1, not IEC 61496. IEC 61496 only covers non-contact, electro-sensitive safeguards such as light curtains, scanners, cameras and radar. The application standard IEC 62046 does cover both kinds together.

Is a light curtain to IEC 61496 enough to reach PL e?

No, IEC 61496 only covers the protective device itself. For PL e, the complete safety function, including the safety relay or safety PLC, contactors and the correct distance, must comply with ISO 13849-1. A Type 4 light curtain is a necessary but not a sufficient condition.

Which edition of IEC 61496-1 is current?

The current version of IEC 61496-1 is the fourth edition from 2020. It moved common requirements from Part 2 into Part 1; the fourth edition of Part 2, published at the same time, adds Type 3 for light curtains. For CE marking, check which EN edition is cited as a harmonised standard in the Official Journal of the EU.

What is an OSSD in IEC 61496?

An OSSD (output signal switching device) is the safety output of an ESPE that switches off as soon as the detection zone is interrupted. In practice it usually consists of two redundant 24 V semiconductor outputs with test pulses. The OSSDs are connected to a safety relay or safety PLC that stops the machine.

📌 In summary

IEC 61496 is the product standard for non-contact safeguards such as light curtains, laser scanners, safety cameras and radar, and its type (2, 3 or 4) determines up to which PL or SIL a device can be used. Always combine it with ISO 13855 for the distance and ISO 13849-1 or IEC 62061 for the complete safety function, so the safeguard actually works as part of machine safety.