SICK WTT12-S Instrucciones De Funcionamiento página 19

4.5 Measures for diagnostic coverage
4.6 Safety functions in the application
4.6.1 Requirements on the detected objects or reference surfaces
1) The angle of incidence and the remission factor may vary, but it must be ensured that the effective reserve is within the specified
corridor (the smaller the angle of incidence, the greater the distance, the smaller the reserve).
8029123/2024/01/15 | SICK
Subject to change without notice
The response times are specified in the technical data,
Diagnostics are required to detect errors with sufficient diagnostic coverage. A distinc‐
tion is made between internal and external diagnostics.
Internal diagnostics are performed online by the device and put the safety outputs in
an error state that requests the safety function performed by the device (the system
changes to the safe-related state).
External diagnostics require an evaluation of the higher-level controller, whereby the
device provides signals for this purpose. Based on this signal, decisions can then be
made to increase the device availability or safety, and actions or decisions can be
triggered in the system.
For the WTT12-S, both internal and external diagnostic measures are required in order
to achieve the required diagnostic coverage. When errors are detected by internal
diagnostics, the digital output is set to the safety-related state by the device itself
(sensor set to INACTIVE).
The external diagnostic measure is based on switching the test input (shifting the
threshold), and evaluation of the resulting behavior of the digital output by a down‐
stream controller (see "Requirements on the higher-level controller", page
Alignment
For both functions, the sensor must be mounted so that the light spot completely hits a
static, non-retroreflective position on the reference object or reference surface.
The sensor can be swiveled, but must be located within its detection corridor (observe
angle to sensing range).
In practice, the detection corridor can be secured by tilting the sensor beyond the
desired setting in relation to the reference surface and ensuring that it switches off in
the process. If the operative reserve is too small, the detection function will be lost and
the cyclical test will fail, thereby potentially impairing the availability but not the safety
function.
• The effective remission factor of the objects must be within the specified range,
see "Data sheet", page
right angle or if the object has a shiny surface, the effective remission factor
is reduced.
1)
•
The reference surfaces must not have any highly reflective surfaces. Highly reflec‐
tive surfaces, for example reflectors, distort the measurement.
• The object and the reference surface must be larger than the light spot.
• The distance to the object surface must be at least 50 mm (especially for function
1).
OPERATING INSTRUCTIONS
30. If the light beam does not hit the object at a
O P E R A T I N G I N S T R U C T I O N S | WTT12-S
see "Data sheet", page 30.
21).
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