Troubleshooting The Readers - Allen-Bradley 2755-LS7-SB User Manual

7–2 Maintenance and Troubleshooting
Troubleshooting the
Readers
Publication 2755-6.9
The following table provides a list of the most common operating
problems, probable causes, and corrective actions.
Problem Probable Cause (s)
1. Host cable defective or
not wired properly.
2. Wrong configuration
Menus do not
command (or lower
display when
case d) entered.
configuration configuration
command is sent.
3. Reader configuration
settings do not match
host's.
1. Host and reader baud
Getting
rates or parity not
unintelligible code.
matched.
1. Wrong label type or
different label type being
scanned than that
enabled in firmware.
2. Incorrect label range or
label too long to be
Menu display but
totally covered by scan
no decode rate in
beam.
decode rate test decode rate test
3. Poor label quality.
(<C>). (<C>).
4. Excessive ambient light,
sunlight, or strobes.
5. Object detector or
another reader is
interfering with reads.
Low decode rates 1. Poor label, range,
during decode rate placement, etc.
test (<C>).
1. Object detector not
positioned properly.
2. End of Read Cycle not
properly defined.
3.. Reader not triggered
when in external mode.
Decode rate okay Decode rate okay
but not getting any
4. Reader not triggered
output (including
when in serial mode.
no reads) in
triggered mode.
5. Label misaligned or
reflecting direct laser
light.
Table continued on the next page.
Corrective Action
1. Check cable connections and wiring.
2. Verify that a <D> serial command (with an
upper case D) is being entered.
3. Reset reader to default and/or match host
settings with reader's.
1. Check baud rates and parity and change to
match the host's settings.
1. Check label configuration settings to be certain
that they match the label type being scanned.
If label type is in doubt, enable
Autodiscriminate All Codes (<P> command).
Also ensure that fixed length and check sums,
if enabled, are set correctly.
2. Reposition label and check the decode rate
(<C> command).
3. Try a readable label.
4. Shield the bar code and/or scan head to verify
that excessive light is not the problem.
5. Remount, eliminate interference, or shielding.
(Many object detectors emit pulsed infrared
signals that can seriously degrade the decode
rate if they shine into the reader or onto
the bar code label when it is being read.)
1. Use better quality labels, place reader closer
to label, etc.
1. Ensure read cycle is active during the time the
label is in the scan line.
2. Ensure that the proper End of Read Cycle is
defined in reader configuration.
3. Ensure trigger device is operating properly.
Also do a Decode Rate Test <C>. If it reads
successfully, the problem is triggering.
4. Ensure that correct serial trigger character is
entered with start/stop characters (a left angle
bracket < (unless redefined) and a right angle
bracket >).
5. Ensure the label is not excessively skewed,
tilted, or otherwise disoriented. Ensure the bar
code is in the scan line when it is supposed to
be. Ensure that the bar code is pitched or
skewed slightly so as to avoid spicular
reflection.