External Device Monitoring (Edm); Device Functions Of The Le 20 Muting - SICK LE20 Instrucciones De Operación

Chapter 3
WARNING
WARNING
2 9 8
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Product description
Make sure that the restart pushbutton is installed at a
suitable location!
The restart pushbutton must be installed so that it cannot be
pressed from inside the hazardous area and that operators have a
clear view of the entire hazardous area when pressing the
pushbutton.
A yellow LED indicates that the evaluation unit is waiting for the
restart command. The restart interlock is activated when 0 V is
applied to the RES DISABLE terminal and deactivated by 24 V
being applied to RES DISABLE.
The restart interlock will not function if RES DISABLE
is deactivated!
If the restart interlock has been deactivated via the RES DISABLE
terminal, the machine control unit must provide the restart locking
function.
3 . 3 . 3

External device monitoring (EDM)

The external device monitoring function checks whether the connected
switching device (relay, contactor, etc.) is OK and that no contacts are
welded. To allow this, the evaluation unit processes the back-checking
signal arriving at the EDM (External Device Monitoring) terminal from
the NC contacts. If an error is detected, the LE 20 disables the OSSD
outputs and assumes the fault status. Repeated closing attempts are
possible if the restart function is active. The signal change at the EDM
input must occur within 300 ms. 24 V must be applied if the switching
contacts are closed. The external device monitoring function is
activated by connecting 0 V at the EDM ENABLE terminal and
deactivated by 24 V applied at EDM DISABLE.
3.4

Device functions of the LE 20 Muting

The LE 20 Muting safety evaluation unit is used if certain objects, e.g.
material pallets, are to be allowed to pass through the hazardous area.
In such cases, it disables monitoring of the photoelectric safety switch
for the time it takes the objects to be transported through the light
beams of the photoelectric safety switches. During this time, additional
muting sensors detect the presence of the material to be transported.
The type of sensors and their layout allow a distinction to be made
between the object and personnel. It is possible to connect two, three,
or four muting sensors to the safety evaluation unit.
Operating Instructions
Safety Evaluation Unit LE 20
8 008 685/Q913/2007-05-21