M
Machine Primary Control Element (MPCE)
An electrically powered element, external to the safety system, which
directly controls the machine’s normal
operating
motion
in such a way
that the element is last (in
time)
to operate when machine
motion
is
either
initiated
or arrested.
Machine Response Time
The
time
between the
activation
of a machine stopping device and the
instant when the dangerous parts of the machine reach a safe state by
being brought to rest.
Minimum Object
Sensitivity
(MOS)
The minimum-diameter object that a safety light screen system can
reliably detect. Objects of this diameter or greater will be detected
anywhere in the
defined
area. A smaller object can pass undetected
through the light if it passes exactly midway between two adjacent light
beams. Also known as MODS (Minimum Object
Detection
Size). See also
Specified
Test Piece.
Muting
The
automatic
suspension of the safeguarding
function
of a safety device
during a non-hazardous
portion
of the machine cycle.
O
Off
State
The state in which the output circuit is interrupted and does not permit
the
flow
of current.
On State
The state in which the output circuit is complete and permits the
flow
of
current.
Open-Closed Debounce Time
The
time
it takes to bridge a
jittery
input signal or bouncing of the input
contacts to prevent an unwanted start of the machine. Adjustable from
10 ms to 500 ms. The default value is 50 ms. A longer open-closed
debounce
time
will also
affect
the recovery
time
of the Controller.
OSHA
(Occupational
Safety and Health
Administration)
A U.S. Federal agency, Division of the U.S. Department of Labor, that is
responsible for the
regulation
of workplace safety.
P
Pass-Through Hazard
A pass-through hazard is associated with
applications
where personnel
may pass through a safeguard (which issues a stop command to remove
the hazard), and then
continues
into the guarded area, such as in
perimeter guarding. Subsequently, their presence is no longer detected,
and the related danger becomes the unexpected start or restart of the
machine while personnel are within the guarded area.
PELV
Protected extra-low voltage power supply, for circuits with earth ground.
Per IEC 61140: "A PELV system is an electrical system in which the
voltage cannot exceed ELV (25 V ac rms or 60 V ripple free dc) under
normal
conditions,
and under single-fault
conditions,
except earth faults
in other circuits."
Point of
Operation
The
location
of a machine where material or a workpiece is
positioned
and a machine
function
is performed upon it.
PSDI (Presence-Sensing Device
Initiation)
An
application
in which a presence-sensing device is used to actually start
the cycle of a machine. In a typical
situation,
an operator manually
positions
a part in the machine for the
operation.
When the operator
moves out of the danger area, the presence sensing device starts the
machine (no start switch is used). The machine cycle runs to
completion,
and the operator can then insert a new part and start another cycle. The
presence sensing device
continually
guards the machine. Single-break
mode is used when the part is
automatically
ejected
after
the machine
operation.
Double-break mode is used when the part is both inserted (to
begin the
operation)
and removed
(after
the
operation)
by the operator.
PSDI is commonly confused with "Trip
Initiate."
PSDI is
defined
in OSHA
CFR1910.217. Banner safety light screen systems may not be used as
PSDI devices on mechanical power presses, per OSHA
regulation
29 CFR
1910.217.
Q
Qualified
Person
A person who, by possession of a recognized degree or
certificate
of
professional training, or who, by extensive knowledge, training and
experience, has successfully demonstrated the ability to solve problems
relating
to the subject
matter
and work.
R
Receiver
The light-receiving component of a safety light screen system,
consisting
of a row of synchronized phototransistors. The receiver, together with
the
emitter
(placed opposite), creates a "screen of light" called the
defined
area.
Reduced
Resolution
A feature that allows a safety light screen system to be
configured
to
produce an
intentionally
disabled light beam(s) within the light screen,
which increases the minimum object
sensitivity.
The disabled beam(s)
appears to move up and down
("float")
in order to allow the feeding of
an object through the
defined
area at any point without tripping the
safety outputs (for example, OSSDs) and causing a Trip or Latch
condition.
Sometimes
called
"Floating
Blanking."
Reset
The use of a manually operated switch to restore the safety outputs to
the On state from a lockout or a Latch
condition.
Resolution
See Minimum Object
Sensitivity
Run Signal
The input signal monitored by the Controller that, when detected, causes
one or more safety outputs to turn On if their other associated input
signals are also in the Run state. In this manual, either the input device or
the device signal is said to be in the Run state
EZ-SCREEN
®
Type 2 Light Screen
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