|Release time:2013-02-28 Source:admin Reads:|
UPC-A barcodes can be printed at various densities as barcode labels to accommodate a variety of printing and scanning processes. The significant dimensional parameter is called x-dimension, the ideal width of single module element. A single x-dimension must be used uniformly within a given UPC-A barcode. The width of each bar and space is determined by multiplying the x-dimension by the module width of each bar or space (1, 2, 3, or 4 units). Visually, a grouping of two or more adjacent bars appear as a single wide bar, while a grouping of two or more adjacent spaces appear as a single wide space. Since the guard bars each include two bars, and each of the 12 digits of the UPC-A barcode consists of two (wide) bars and two (wide) spaces, all UPC-A barcodes consist of exactly (3×2)+(12×2)=30 (wide) bars, of which 24 represent numerical digits and 6 represent guard bars.
The x-dimension for the UPC-A barcode labels at the nominal size is 0.33mm (
A quiet zone, with a width of at least 9 times the x-dimension, must be present on each side of the scannable area of the UPC-A barcode labels. UPC-E requires 9 X-dimension units on the left side and 7 on the right. For a GTIN-12 number encoded in a UPC-A barcode symbol, the first and last digits are always placed outside the symbol to indicate the quiet zones that are necessary for barcode scanners to work properly.