Short Description Of The Ls4 As-Interface; Short Description Of As-Interface Safety At Work - Siemens SIGUARD LS4-4 Anleitung

In view of its integrated AS-Interface, the LS4 AS-Interface can be connected to the
AS-Interface bus system. If a person or obstacle is situated within the protective fields
that have been defined earlier, a safety-related switching function will be triggered and
the machine that is protected by means of the AS-Interface and the AS-Interface safety
monitor will be brought into a safe state. This switching function will only be reset when
the protective field is clear, irrespective of the operating mode, which may be automatic
or may involve acknowledgement by way of the AS-Interface safety monitor.
2.1

Short description of the LS4 AS-Interface

The LS4 AS-Interface area scanner sends out extremely short laser pulses, and
measures the time between the impacting of a pulse on an object and its being
reflected back to the receiver of the LS4 AS-Interface. The length of time enables the
device to calculate the distance between the object and the LS4 AS-Interface.
The polling unit in the scanner rotates, and sends out / receives a laser pulse at
intervals of 0.36°. In this way a sector of a circle of up to 190° can be polled, the LS4
AS-Interface being located at the midpoint. The protective field that is to be monitored
is limited by a user-defined curve around the scanner, the maximum distance from this
to the midpoint of the scanner being 4 metres. If an object is detected between this
boundary line and the scanner, thus violating the protective field, the scanner will
switch off its safety-related OSSD output, and the status of the OSSDs will be
transmitted to the AS-Interface safety monitor by way of the AS-i system in the form of
a cyclic data sequence; having been notified of the violation of the protective field, the
monitor will bring the hazardous movement to a halt.
In addition to the safety-related protective field, a non-safety-related warning field can
be parameterised; when this is violated the system will not be switched off, but a
warning signal will be given. This will likewise be included in the data telegram that is
exchanged cyclically with the bus master and can be called up at will.
Although the data transfer is safety-related, the warning signal should not be used in a
safety-related manner, as it is not delivered by the scanner as a safe signal.
The protective field and the warning field together constitute a pair of protective fields.
They are always activated jointly, and a maximum of four protective fields may be
selected at any time. All pairs of protective fields, as well as the permissible modes of
switching between them, will be adapted to the given application when the system is
first put into operation. When the system is operational, switching between protective
field pairs is managed by local sensor signals.
2.2

Short description of AS-Interface Safety at Work

The actuator-sensor-interface (AS-Interface) has been set up as a system for linking in
a network sensors and actuators (principally binary ones) at the lowest level of the
automation hierarchy. The great quantity of installed systems, the ease of operation
and the reliable operation of the AS-Interface make it an interesting option for purposes
of machine safety.
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