electronic control systems is another important standard. It's based on a risk assessment and reduction strategy for safety control functions like light curtains and safety laser scanners. It includes functional requirements specifications and safety integrity level (SIL) requirements. Examples of functional requirements include frequency of operation, response time, operating modes, duty cycles, operating environment, fault reaction functions, and so on. The resulting SILs are measured on a scale from 1 to 4 (Figure 2). ISO 13855 defines how to place scanners with respect to a person's approach. For example, if a scanner is mounted at a height of 300 mm, a resolution of 70 mm is sufficient to detect a human leg. At lower mounting heights, the recommended minimum resolution is 50 mm. Scanner specifications Once it's been determined that a safety laser scanner satisfies the application requirements and can support the needed level of safety, it's time to consider specifications. Examples of important scanner specifications include: Scan angle. Several scan angles are available, such as 190°, 270°, and 275°. The scan angle and its
Figure 2: Safety laser scanners meet the criteria of PLd and SIL3 and are suitable for use in applications where safety is important. (Image source: SICK)
Figure 3: Commissioning can be sped up by using a scanner that uses scanned data for automatic configuration to identify stationary objects in the warning zones. (Image source: IDEC)
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