Microscan MS-4 User Manual page 104

Trigger Mode and Duration
External Level
Usage: This mode is effective in an application where the speeds of the conveying
apparatus are variable and the time the Imager spends reading each object
is not predictable. It also allows the user to determine if a No Read has
occurred.
Definition: External Level allows the read cycle (active state) to begin when a trigger
(change of state) from an external sensing device is received. The read
cycle persists until the object moves out of the sensor range and the active
trigger state changes again.
Serial Cmd: <K200,2>
Important: Level and Edge apply to the active logic state (Negative or Positive) that exists
while the object is in a read cycle, between the rising edge and the falling edge. Rising edge
is the trigger signal associated with the appearance of an object. Falling edge is the trigger
signal associated with the subsequent disappearance of the object. This applies both to
External Level and External Edge.
External Edge
Usage: This mode is highly recommended in any application where conveying
speed is constant, or if spacing, object size, or read cycle timeouts are
consistent.
Definition: External Edge, as with Level, allows the read cycle (active state) to begin
when a trigger (change of state) from an external sensing device is
received. However, the passing of an object out of sensor range does not
end the read cycle. The read cycle ends with a good read output, or,
depending on the End of Read Cycle setting, a timeout or new trigger
occurs.
Serial Cmd: <K200,3>
5-8
Initiate Read Cycle:
Object #1, moving in front of the
detector beam, causes a
change in the trigger state,
which initiates the read cycle.
End Read Cycle:
The same object, moving out of
the detector beam, causes
another change in the trigger
state, which ends the read cycle.
Initiate Read Cycle:
Object # 1, moving in front of the
detector beam, causes a change in
the trigger state, which initiates the
read cycle.
Initiate Second Read Cycle:
Object # 2, moving in front of the
detector beam, causes another
change in the trigger state. This sig-
nal initiates a new read cycle and
ends the previous read cycle unless
Timeout is enabled and a good read
or timeout has not occured.
MS-4 Imager User's Manual