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12
Safety concept
4 Safety
Instruction book, IQAN-MC3
The fully redundant structure for input signals is recommended, since it normally
yields a higher performance level for the sensor arrangement. The IQAN-MC3 will
accept any of the two structures above for all I/O types. The single channel structure
illustrated below is only allowed for VIN, but it is recommended to avoid this since it
normally yieds a low performance level on the input subsystem.
Single structure with limited or no monitoring.
Avoid the single structure without monitoring in safety functions. It is not allowed for
DIN, FIN or DFIN input used in safety functions.
The structure depends largely on how the input is used by the application, to view the
inputs as two redundant channels; they must lead to a safe state independent of each
other.
CAN communication
The IQAN-MC3 has built in support for safe connection to other IQAN-MC3 units. For
more information, see the IQANdesign user manual.
E
XAMPLE
An overload safety function that uses two separate pressure sensors to initate
stopping of a hazardous movement, may have true redundancy if the highest of the
two signals is used for the overload, and the signals are compared with each other as
a diagnostic measure.
• Implemented in IQANdesign with 2 VIN channels, the method ’MaxOf’ and
with AAC (Analog-Analog Comparator)
If the same overload function only uses one of the signals, and compares with the
other for diagnostics that lead to a safe state, that is not true redundancy, but may be
interpreted as a single structure with monitoring by separate signal.
• Implemented in IQANdesign with 2 VIN channels and with AAC
Connecting pairs of signals.
The wiring is the same for both alternatives.
IN 1
Not recommended!
IQAN-MC 3
OUTPUT
S UB S Y S TEM
(e.g. v a lve s )
u
u
IQAN-MC3
+VREF
-VREF
VIN secondary
VIN primary
Sensor 2
Sensor 1