QX-830 Compact Industrial Scanner User’s Manual 5-67
Scanner Parameters
Tracking
Tracking is the frequency detection value that determines the threshold between a white
bar and a black bar. This is a range of frequencies that have been divided into 127 steps.
For most applications, the default tracking value (40) is robust enough to deal with most
marginal signals. However, in some instances, symbols are printed on a “noisy” substrate,
or symbols are relatively distant from the scanner and the signal-to-noise ratio and optical
focus are not ideal. In such cases, using a combination of Gain Level and Tracking can
improve decode performance by rejecting “noise” and correctly recognizing the bars of the
candidate symbol.
Transition Counter
Transition Counter is an integral part of the AGC system. Transition Counter determines
the number of black bars that will be counted before an AGC sample is taken. Setting a
Transition Counter value lower than the default of 14 gives the scanner less integration
time for the candidate symbol, and makes the scanner more susceptible to false objects.
A Transition Counter value greater than 14 requires more bars to be present for the symbol
even to qualify as an object. When setting the Transition Counter value, it is important to
keep in mind what occurs when the symbol is first presented to the scanner—before gain
is applied to the symbol. A few bars are usually missed due to distortion at first. Setting
Transition Counter to the same value as the number of bars contained in the symbol can
cause the scanner not to take an AGC sample at all. The value of 14 is optimal except in
the case of low bar count due to:
• Symbols that are tilted so that only 10 bars or fewer are available in a single scan line.
(See Symbol Reconstruction).
• Symbologies with typically low bar counts, such as Pharmacode. Applications using
symbols with fewer than 10 bars should use Fixed Gain operation.
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