Microscan N2210WZ Owner's Manual page 128

Read Cycle
Additional Information about Gain, Tracking, and Transition Counter
Gain
The QX-870 Industrial Raster Scanner is an optical device. Optical devices deal with a
wide range of brightness, in a way similar to a camera. If the image is too bright, the
exposure must be reduced. If the image is too dark, the exposure must be increased. The
scanner will only work properly if it is within the range of brightness that can resolve light
and dark changes, or "transitions", in the field of view. If the gain is too low, the entire
symbol looks like a dark bar to the scanner. If the gain is too high, the entire symbol looks
like a white bar to the scanner. Brightness conditions can be affected by the distance
between the symbol and scanner, or by the consistency of the material on which the
symbol is printed.
The AGC Sampling Mode
Edge or Continuous) and
AGC (Leading Edge or Continuous)
AGC self-adjusts the optical-electrical gain to hold brightness to one range for all materials
and distances. The Auto Calibration menu shows what AGC is doing to control brightness,
as in the example shown here:
The value –35.0 indicates that brightness has been reduced by 35 dB. The symbol used in
this example was very close to the scanner, using high laser power. As the laser power is
lowered and/or the symbol is moved farther from the scanner, the attenuation (brightness
reduction) value becomes lower. The user does nothing to adjust the gain in order to keep
the scanner decoding; AGC performs the task of raising gain to accommodate the greater distance.
The actual attenuation factor is determined by the return light from the symbol and the
"SETPOINT" value that the control system is attempting to hold. (SETPOINT is an
abstracted number range that has to do with the feedback system's dynamic range.) A
very low SETPOINT value of 0-20 would tend to keep the symbol amplitude low. A very
high SETPOINT value of 150-255 would tend to keep the symbol amplitude high. The gain
will change to hold the feedback value equal to the user SETPOINT setting of amplitude
(Gain Level) at all times.
Disabled (Fixed Gain)
Fixed Gain is a gain mode in which there are no changes in the gain system. The system
takes the total gain range and divides it into 255 steps. Then the value of the
setting is converted directly into the gain value. Nothing will change this value unless the
user changes the Gain Level setting.
5-62
command has two primary functions: AGC (either
Disabled (Fixed Gain).
QX-870 Industrial Raster Scanner User's Manual
Leading
Gain Level