LINK Systems OmniLink II Press Automation Control - Manual (Page 118)

August 30, 2002 Manual Version 1.0 6.13
Sensors that are used as inputs to cyclic channels can be either Normally On or Normally Off. The
event is considered to occur when the sensor switches from its normal state. For example, if a cyclic
channel is programmed to have a Normally Off sensor, the channel event will occur when the sensor is
On. If a cyclic channel is programmed for a Normally On sensor, the channel event will occur when the
sensor is Off. In the majority of applications, the input sensor to a cyclic channel is a Normally Off
sensor.
An additional feature for use on cyclic type channels is the stroke delay counter which is programmable
by the operator. The counter provides the flexibility to use the cyclic type to monitor events in the
production process that may not occur every stroke, but must occur within some number of strokes. An
example of such an application is slug detection, where under normal operation slugs are allowed to
build up and fall out maybe two or three at a time after several strokes. In such a scenario a slug would
not be detected by the sensor on every stroke, this would produce a fault were the stroke delay counter
not used. The delay counter allows the operator to enter a number representing the maximum number of
strokes that can be run consecutively without the slug being detected within the timing window. If the
sensor does not become active within the window for a number of strokes exceeding the counter
number, then a fault will be generated. By contrast, if the sensor does become active within the window
on some stroke before the counter expires, then the counter is reset and the full count is again allowed.
If the operator desires that the sensor be required to become active on every stroke, then a value of zero
should be entered into the counter. (Note that although the sensor is allowed to remain inactive
throughout a stroke when the stroke counter is used, the opposite is not true; e.g., the sensor is not
allowed to remain active through an entire stroke or a fault is generated.)
ACCEPTABLE
UNACCEPTABLE
270
0
180
90 270
0
180
90 270
0
180
90
270
0
180
90 270
0
180
90 270
0
180
90
270
0
180
90
TIMING
WINDOW
EVENT
ON
Figure 6.8 Acceptable and Unacceptable Conditions for Cyclic Input