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Xtium-CL PX4 Reference
Xtium-CL PX4 User's Manual
by the acquisition linescan camera. The Xtium-CL PX4 supports single or dual phase shaft encoder
signals. Dual encoder signals are typically 90 degrees out of phase relative to each other and
provide greater web motion resolution.
Example using any Encoder Input with Pulse-drop Counter
When enabled, the triggered camera acquires one scan line for each shaft encoder pulse-edge. To
optimize the web application, a second Sapera parameter defines the number of triggers to skip
between valid acquisition triggers. The figure below depicts a system where a valid camera trigger
is any pulse edge from either shaft encoder signal. After a trigger, the two following triggers are
ignored (as defined by the Sapera pulse drop parameter).
K
D
D
K
D
D
K
D
D
K
D
D
K
D
D
Shaft Encoder phase A
Shaft Encoder phase B
K = Keep
D = Drop or Skip
Note: in this example, Number of trigger to drop = 2
Line acquired
Figure 17: Encoder Input with Pulse-drop Counter
Example using Sequential Encoder Input
Support of a dual phase encoder should consider the direction of motion of one phase signal to the
other. Such a case might exist where system vibrations and/or conveyor backlash can cause the
encoder to briefly travel backwards. The acquisition device must in those cases count the reverse
steps and subtract the forward steps such that only pulses after the reverse count reaches zero are
considered. By using the event “Shaft Encoder Reverse Counter Overflow”, an application can
monitor an overflow of this counter.
The example figure below shows shaft encoder signals with high jitter. If the acquisition is
triggered when phase B follows phase A, with jitter present phase B may precede phase A. Use of
the Shaft Encoder Direction parameter will prevent false trigger conditions.
Shaft Encoder phase A
Shaft Encoder phase B
Figure 18: Using Shaft Encoder Direction Parameter
Note: Modify camera file parameters easily with the Sapera CamExpert program.
