The signal quality level (bit 0, bit 1), which provides information about the current
quality of the transmitted measurement data, can also be transmitted via the IO-Link
process data. Depending on the value, the following conclusions can be drawn about
the measured values with regard to the statistical measurement accuracy.
Bit 1
Bit 0
Value
Statistical measurement error
1
1
3
< 10 mm
1
0
2
< 25 mm
0
1
1
< 25 mm
0
0
0
Measured value is not trustworthy
NOTE
When using the signal quality level to evaluate the measured value quality, it is nec‐
essary to evaluate each transmitted measured value including signal quality level at
system level. This is the only way to ensure that changes in signal quality can be taken
into account immediately in the decision-making process of the system.
Depending on the application, consistently good signal qualities can be achieved for
small scanning ranges or even materials with a large remission factor. If the signal
quality is output as the value 3, it is possible to take smaller measurement errors of
the device into account in the evaluation or decision-making at system level (<10 mm).
This only applies, however, as long as the value 3 is displayed as the signal quality
level. Otherwise, larger measurement uncertainties must be taken into account. The
validation of the safety function that processes the measured values in conjunction
with the signal quality must be performed by the system integrator of the application.
On the other hand, by outputting the value 0, for example in the event of short-term
faults in the application (covered by the max. cumulative downtime per year), it is
possible to immediately recognize that the currently transmitted measured values are
not trustworthy and must not be used for further processing. It is then possible for
the higher-level system to rely on other data at this point in time or to perform a
degradation of the safety function.
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PROJECT PLANNING
54
O P E R A T I N G I N S T R U C T I O N S | DT35S
8027663//2022-08-04 | SICK
Subject to change without notice