is active, the outputs for measured values output an invalid value or an error value. The
outputs then go back to the previous state. The switching output as an alarm output
changes to the active state and back during the test or remains there if the alarm state
already existed before.
According to ISO 13849 4.5.4, a test or diagnostic rate equal to at least 100 times the
demand rate of the safety function is prescribed for category 2. The periodic switching
off and on of the laser must therefore always be adjusted for the demand rate and
evaluated in the application.
These diagnostic measures enable faults in the logic and output path of the device to
be detected.
9.8.2
DC = 60% target value
In order to achieve a DC of 60% for the complete device despite inadequate internal
self-diagnostics, both internal and external diagnostic measures must be performed
in order to obtain sufficient diagnostic coverage for the complete device (optical path,
logic, output path). A DC of 60% can thus only be achieved with external diagnostics in
the system network, taking into account an evaluation unit (controller) designed for this
purpose. The device does not have a DC of 60% based on its internal diagnostics!
The table shows the possible combinations of diagnostic measures to achieve a DC of
60% depending on the interface used. To achieve a DC of 60%, a diagnostic measure 1
must always be linked to a diagnostic measure 2.
Table 6: Diagnostic measures for DC = 60%
Interface used
for diagnostics
Diagnostic measure 1
Diagnostic measure 2
Achieved
DC
Digital outputs
Switching function alarm func‐
tion
Laser off/on system response
60 %
Switching function signal level
warning
Laser off/on system response
Analog current
output
Clamp alarm function
Laser off/on system response
IO-Link
Clamp alarm function
IO-Link timeout
Laser off/on system response
Switching function alarm func‐
tion (status bit)
IO-Link timeout
Laser off/on system response
Switching function signal level
warning (status bit)
IO-Link timeout
Laser off/on system response
9.8.3
Measures to improve sensor fusion at the system level
If the safety-related measured values are to be used via the IO-Link process data for
a safety function at system level, e.g., also in combination or in fusion with further
device data, the confidence of the transmitted measured values at the current time can
be decisive. The confidence of the measured values depends to a large extent on the
systematic and statistical measurement error of the device.
The systematic measurement error is < 25 mm over the entire temperature range as
well as over the entire safety-related detection range.
The safety-related statistical error of the device is also < 25 mm over the entire
detection range, which corresponds to a coverage probability of 4.4 σ according to
IEC TS 62998-1 and is the required value for Performance Class B. This measurement
uncertainty must be taken into account in addition to the systematic error when making
a decision at system level based on the device measurement data.
PROJECT PLANNING
9
8027663//2022-08-04 | SICK
O P E R A T I N G I N S T R U C T I O N S | DT35S
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Subject to change without notice