IDEC DATAVS1 Series - Manual (Page 70)

Instruction Manual SVS1 Series
65
9. SELECTING AN INSPECTION USING THE DIGITAL INPUTS
By using a special protocol it is possible to use the digital inputs to select the inspection to be
performed on the SVS.
The protocol comprises a prologue followed by an epilogue.
The prologue consists in 3 impulses with a minimum duration of 10 msec and a 50% duty cycle.
The first impulse opens the prologue window, for a maximum of 80 msec, during which 3 impulses are
expected in order to enable the inspection selection phase. At the end of the prologue, if only 3
impulses have been counted, it moves onto the next phase.
In the inspection selection window, the number of impulses are counted for a time of 250 msec, which
corresponds to the number of the selected inspection. If the number of impulses does not match the
valid inspection numbers, the request is refused.
The diagram below shows the image (acquired using an oscilloscope) of the number 8 inspection
selection process with the digital inputs generated by a PLC.
Selecting inspection number 8
Delay in the change of inspection
Before the inspection is enabled, it is necessary to wait for the inspection start-up to be concluded. As
this start-up time depends on how complex the inspection is, there is no specific and single parameter
for the time needed to switch from one inspection tool to another.
If the inspection process uses very fast tools, such as an edgecount or width count, the switch will
require a time of around 100 msec. If, on the contrary, the inspection process uses very slow tools,
such as a complex pattern match, the time needed to switch from one inspection tool to another could
be around 1 - 2 seconds.
During the inspection switch, the sensor suspends the acquisition of images and enters into idle mode,
then the sensor signals with a flash of the illuminator that the new inspection activity has begun.