What is meant by Code Density or X-Dimension?
Both have to do with how much space the printed barcode symbol takes up. The length of the symbol from first bar to last depends directly on the width of the individual elements in the code. Since there are both wide and narrow elements (a bar or space is an element), lets talk first about how much wider the wide elements are than the narrow ones. Most code specifications specify a range for the ratio of the wide to narrow elements. Generally this is between 2.2:1 to 3.0: 1. In general, a middle-of -the-road figure of 2.5:1 is used as the nominal printing specification.
When we talk about barcode printing density we usually refer to it in one of two ways, either by the size of the narrow element in the code or the number of characters that can be encoded per inch of code length. In our end of the business we usually always measure code density by the width of the narrow element. This is also referred to as the code's X-Dimension. Codes with an X-Dimension of less than 0.01 inch are considered to be high density codes. Codes with X-Dimensions between 0.01 and 0.025 inch are considered to be medium density and codes with larger X-Dimensions are considered to be low density.
Usually barcode reading optics are not designed to read all code densities. Obviously a very narrow reading aperture is necessary to read high density codes. The same narrow aperture could theoretically be used to read low density codes also. However, low density codes are not, in many cases, printed with the same quality or the same printing methods as high density codes. For example a low density code may be printed with a dot matrix printer. In this case a very narrow aperture could see the individual dots, and spaces between the dots, causing a misread of the code. In general, when specifying a barcode scanner, giving the scanner manufacturer information regarding the code density and the printing process will minimize any potential scanning problems.