Adjusting Scanner Gain And Offset - Hand Held Products SV Series User Manual

Adjusting Scanner Gain and Offset

Scanner gain and offset adjustment via commands is available in SV units that
have the "A" circled on the label that indicates focus distance. The adjustment
capability is useful for adapting the unit to various material types and scanning
angles during the setup procedure. Knowledge of Hand Held Products'
ScanView software is required for best understanding of the following
description.
When setting SV scanner gain and offset, use ScanView Reflectance Profile
Mode as the guide to viewing signal levels. The object is to have at least 6 lines
high of signal amplitude for the bar code(s) being verified. The bar code signal
vertical placement (offset) should be within the yellow lines to ensure the signal
is in the linear range. All other objects' amplitudes and placements are not
important. A picture of a "good" signal level is shown on
To adjust gain and offset settings, first use the ScanView Transmit SV
Commands Screen to send a ~HT command to the SV unit. In the reply, look for
the line that reads [DACs] = nnn nnn nnn nnn where nnn = numeric values.
Example: a unit may read: [DACs] = 201 146 255 255. This indicates the current
settings.
1. The 201 indicates the value of the gain setting. The higher the value,
the higher the gain and therefore the higher the amplitude of the scan
profile for a symbol. Max value is about 225.
2. The 146 value indicates the offset setting. The higher the value, the
lower the symbol placement is offset on the graph.
3. The command ~Hd101nnn sets gain where nnn is the three digit value.
4. The command ~Hd201nnn sets offset where nnn is the three digit
value.
5. Use these commands to set the desired signal amplitude ( ~Hd101nnn)
and locate the signal vertical placement between the yellow lines (
~Hd201nnn.)
6. A few iterations of commands will probably be needed, therefore it will
be necessary to access the Transmit SV Commands Screen and
Reflectance Profile Mode alternately.
Note: A short cut to the Reflectance Profile Mode is accessed by pressing F3.
7. Like most other SV commands – new scanner settings are enabled
immediately when received, but to be stored to non-volatile memory so
they are maintained on a power up condition, the ~Hx command must
be transmitted after the desired settings are achieved.
5 - 10 Quick Check® SV Series User's Guide
page 5-11.