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Practical, standards-based insight on machine safety and industrial sensing from DAIDISIKE engineers — the background behind specifying the right product with confidence.
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What "Type 4" Means on a Safety Light Curtain
Electro-sensitive protective equipment (ESPE) is classified by Type under IEC 61496-1. Type 4 is the highest integrity level and is required for high-risk hazards; Type 2 suits lower-risk applications. The Type determines the internal architecture and diagnostics a curtain must have — it is not a marketing label. Match the Type to the Performance Level (PL) your machine risk assessment demands under ISO 13849-1.
See our Type 4 light curtains →Safety Laser Scanner vs Safety Light Curtain — When to Use Each
A light curtain guards a flat opening with a fixed plane of beams. A safety laser scanner sweeps a horizontal area and can guard a whole floor zone from one corner, with switchable warning and protective fields — ideal for AGVs and area guarding. Curtains give finer resolution (finger/hand detection); scanners cover area and mobile platforms. Both must carry a real safety rating (Type / SIL / PL) to protect a person.
Explore the ST27 safety scanner →Why Protective Range Is Specified at 1.8% Remission
A safety scanner or curtain must detect the worst-case target: dark, non-reflective clothing. That is why a protective field is specified at 1.8% remission — the value the ISO 13855 safety-distance calculation must use. Longer "warning" or "measuring" figures are quoted at 10% or higher remission and have no safety function. Comparing a 20 m detection number against a 5 m protective field is comparing two different things.
How protective range works →Measuring LiDAR vs Safety LiDAR — Not Interchangeable
Obstacle-avoidance and measuring LiDAR sensors output ordinary discrete or Ethernet data and carry no Type, SIL, Category or PL rating. They are excellent for navigation, anti-collision and dimensioning — but they must never be the protective device that stops a machine to protect a person. That role needs a safety-rated laser scanner with OSSD outputs.
Compare our LiDAR range →Guard Locking vs Simple Interlock on Machine Doors
A simple interlock switch only tells the control the guard is open or closed. A guard-locking switch physically holds the door shut until the machine is safe — essential where the machine coasts down or stores energy after a stop. Coding level matters too: RFID-coded switches resist defeat far better than magnetic or mechanical actuators.
See safety door switches →NPN vs PNP: Matching a Sensor Output to Your PLC
An NPN (sinking) output switches the signal line to 0 V; a PNP (sourcing) output switches it to +V. European and North American controls are usually PNP/sourcing; many Japanese controls are NPN/sinking. Ordering the wrong polarity means the sensor will not read correctly on your input card — confirm the input type before you specify.
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