HandHeld Entertainment SV Series Manual do Utilizador descarregar pdf (Página 117)

Quick Check® SV Series User’s Guide A - 5

Figure 3 - Examples of Scan Profile Parameters Out of Range

Calibration Hints

Calibration is used to normalize reflectance calculations to known (and/or

traceable) values in absolute units of % reflectance. Calibration affects

reflectance calculations only. Calibration does not affect any other calculations

or ability to decode a symbol, etc. The scanner gain and offset settings have the

major effect on scanning performance. Keeping the scanner signal linear

(between the yellow lines as described previously) is very helpful for good

decoding, but is CRUCIAL for reflectance measurements. The calibration

procedure will not be successful unless the bar code signal is proper.

There may be cases in applications where the material being analyzed requires

a scanner gain and offset setting that will not allow calibration with the standard

SV calibration symbol. In most cases this is due to a low contrast material (such

as brown corrugated) that will make the signal level on the calibration symbol go

past the yellow lines. In cases like this there are two basic choices to make:

1. Do not use parameters that involve absolute units of reflectance as fail-

ure criteria. These parameters include Symbol Contrast, Overall ISO

Grade, PCS, Rmax, and Rmin.

2. If reflectance parameters are required to be analyzed in the application,

a calibration symbol can be created from the material being analyzed.

Contact Hand Held Products Technical Assistance (see page 9-1) for

details.

All of bar code

signal not

lines

Bottom of bar

code signal

not “flat”

between yellow

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HandHeld Entertainment SV Series Manual do Utilizador Página 117