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Radar or optical?

With the recent introduction of the Leuze safety radar LBK, the safety world is investigating where it can be used instead of an (optical) safety laser scanner such as the Leuze RSL 400 or a safety light curtain. 


Both principles are very different. The safety radar looks for movement to determine if a body is detected. The radar wave is emitted by the sensor and will deflect at different distances depending on the movement. This is especially useful when detecting the human body or other fixed moving objects (e.g. a robot, AGV, etc.), resulting in a safe condition (i.e. stopping dangerous machine movements or processes). In contrast, static objects do not move and are ignored (e.g. a pillar or fixed machine part).

Security scanners and light curtains use optical technology according to the scan and transmitter/receiver principle. The secure optical sensor emits infrared light and expects this light back into the receiver. Thus, if no light is detected, there is an unknown situation and the device turns off its safe outputs, resulting in a safe condition. As a result, fingers, hands or legs do not enter the danger zone.

Safety radars are extremely robust to environmental conditions such as cold, snow, water, smoke, dirt, oil, debris. Many static non-metallic objects such as foam, plastic, wood and even concrete are invisible to the safety radar: radar waves pass right through these materials.

The Leuze AHU safety radar and controller are classified in safety category 2, PL d is used for preventing the restart of dangerous movement within a workstation/robot cell or as a walk-in protection.

The Leuze RSL400 safety scanner is classified in safety category 3, PL d and is often used for area monitoring, access and restart protection. Applications include robotic protection, Automated Guided Vehicles (AGV) and - when mounted vertically - as an interlocking or walk-in guard.

A safety light curtain (such as the Leuze MLC500) belongs to the highest safety category 4, PL e. This device is the workhorse of the industry, used for most safety applications and needs. Extremely fast response time, with secure outputs, in many lengths and resolutions.

One important difference between radar and optical safety devices is resolution: radar does recognise a hand moving in the safety field, but this is not guaranteed. Radar has been developed to recognise large objects. What this is depends on the material, speed and position of the object. 

Optical security devices such as the RSL400 scanner can be configured via software to detect objects such as a person's hand, wrist or ankle. 

Speaking of configuration, safety radars and safety laser scanners are usually configured via software. For example, the protection (or warning) field can be selected, inputs and outputs configured and other functions. The safety scanner is usually much more configurable because the optical sensor can scan measurements almost down to the millimetre, while the radar is accurate to around 300 mm.

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