Banner A-GAGE MINI-ARRAY Series - Manual (Page 20)

Control Module Configuration
20
4.5 Scanning Methods
The control module offers the choice of one of four scanning methods:
• Straight scan
• Interlaced scan
• Edge scan
• Skip scan
Straight Scan is the default mode in which all beams are scanned in sequence from the
bottom end (cable end) to the top end of the array. This scanning method requires the
longest scan times and provides the smallest object detection size.
To calculate scan time for Straight Scan, multiply the number of beams by 55
microseconds, and add post process time.
Interlaced Scan alternates a straight scan with a slanted-beam scan to improve optical
resolution within the middle one-third of the scanning range (see Figure 4-1). A slanted-
beam scan begins with a beam between emitter channel 1 and receiver channel 2, then
between emitter channel 2 and receiver channel 3, and so on. The last emitter channel
beams to the last receiver channel to complete the scan. After this sequence, the emitter/
receiver pair performs a standard straight-across scan (emitter channel 1 – receiver
channel 1, and so on).
To calculate scan time for Interlaced Scan, double the number of beams in the array,
multiply by 55 microseconds, and add post process time.
Edge Scan is designed to speed sensing response time, by measuring or locating only
one edge of an object. Edge scan activates only the beams located near the top edge of
an object in the light screen. (NOTE: “Top edge” refers to the edge of the object passing
farthest from the cabled end of the sensors.) When the array is clear, the system will
execute straight scans. Edge scan begins when a blocked channel is detected. Each scan
begins six beams prior to the last beam blocked during the previous scan. The scan
continues from this point and moves upward to the first unblocked beam, where the scan
is completed. Use of Edge Scan mode limits the Scan Analysis mode selection to only
LBB (Last Beam Blocked). Edge Scan requires the following configuration: Analysis Mode
1 – LLB; Anaylsis Mode 2 – None; and all beams active (no blanking).
Scan time for Edge Scan mode will vary, depending on what size objects are in the array
at a given time.
Skip Scan speeds sensing response time at the expense of decreased sensing resolution.
Skip Scan mode allows from one to seven beams to be skipped during each scan. For
example, with one beam skipped, only beams 1, 3, 5, 7, etc. will be interrogated; with
two beams skipped, only beams 1, 4, 7, 10, etc. will be interrogated. Skip Scan also has
some restrictions: the object should provide a solid obstruction, and the size of the
object will determine the maximum step size (the target object cannot be smaller than
the distance between two consecutive beams).
To calculate scan time for Skip Scan, first determine how many beams are being used. (For
example, if the array has 16 beams, and it is configured to skip 1 beam, then half the
beams – 8 – are in use. If the array is configured to skip 3 beams, then every fourth beam
– a total of 4 for this array – is in use.) Multiply the number of beams by 55 microseconds,
and add post process time.
Post Process Time
Post process time is determined by the number of beams “fired” in a given scan, and
measured in milliseconds. To compute post process time, use the following formula:
PPT* (in milliseconds) =
(
Beam Channels Fired + 10
)
x 0.12 ms +1 ms
8
* Approximate Value
Resolution is
increased in
the center
third of
the range
Figure 4-1. Interlaced Scan Mode improves
optical resolution in the middle
third of the scanning range.
Banner Engineering Corp. • Minneapolis, U.S.A.
Website: http://www.baneng.com • Tel: 888.373.6767