A Scanner Misread Bar Codes

Article ID: 78728309


User reads bar code with a scanner and the characters that appear on the PC monitor are incorrect.

Root Cause

The bar code could contain voids and spots. If a bar code contains voids or spots in the bars or spaces, it is quite possible for a scanner to misread the bar code. A void is when part of the black line in a bar code is missing and can cause the scanner to measure the white space between the bar code lines to be larger than it should be measured, thus causing the wrong data (ASCII key code) to be sent to the host. In the same way a spot in the middle of the white spaces could cause the scanner to interpret the white space to be smaller than what it should be, causing the scanner to interpret the bar code incorrectly and send the wrong data (ASCII key codes) to the host.


The image below is an example of a bar code with Voids in the black bars of the code:
User-added image
The image below is an example of a bar code with Spots in the white spaces:
User-added image

Scan a security level for the scanner that will make the scanner read the bar code more than once before sending data to the computer.

Almost all Zebra scanners can be enabled for different levels of security.  Enabling a security level will cause the scanner to read the bar codes more than once before sending the data to the host.  Refer to the appropriate Product Reference Guide for security level programming of the scanner in question.

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