Hello, I'm Peter. I'm working in a PDA manufacturing company and my main job is related to bar-code modules. On this post, I'll tell you how to choose a bar-code module which suits you. 

First, you need to know what type of bar-code readers you are looking for if you want to buy a bar-code reader(PDAs, Bluetooth readers, USB type readers, etc). There are so many bar-codes that each device can read or cannot, so you need to be careful not to choose a wrong one. There are so many things to check about options, but I'll tell you 3 main points that you should check first.  

1. Bar-Code Type

Basically, there are two types of bar-codes, one dimension and two dimensions.

one dimension (A.K.A 1D)

 two dimensions ( A.K.A 2D)

'Dimension' means the dimensions of information. An 1D bar-code can have linear data only. So, the width of an 1D bar-code is wider than a 2D bar-code about the same data. Now, some people might think like this.

'Oh, then I will use a 2D bar-code.'

One thing you should know is that 2D bar-code modules are usually more expensive than 1D bar-code modules. This is because 2D modules are almost like cameras and 1D modules are just laser readers (some are similar to 2D modules but I will cover this later). 

If the information you need to read is enough for 1D bar-codes, you'd better buy an 1D module device. Otherwise, you need to buy a 2D bar-code module device.

2. Density 

The density of bar-codes is another very import point to choose bar-code modules, but people usually don't know about this point. The density of bar-codes is calculated by mil( 1/1000 inch). If you want to generate a bar-code, you need to know mils of the bar-code. Density is not the size of bar-codes, but the size is related to the density like the below.

20mil QR bar-code

 50mil QR bar-code

The density of bar-code should be thicker than 5mil to 7mil. There are, of course, modules which can read less than 5mil codes, but they are special ones. I recommend you to generate bar-codes over 10mil to make them be read easily. 

There are many factors that disturb a module to read codes: the reflectance of the surface of codes, contamination, aging, problems from a printer, and etc. If you make thicker density bar-codes, it will be helpful to overcome the factors disturb a module to read codes. In other words, modules with thicker density are easier to be read. Therefore, to print bar-codes properly, the density over 10mil is recommended. 

3. Reading Distance

If you use a bar-code reader at a small shop, it won't be a matter as you will read bar-codes within 20cm distance. However, in some cases, you need to read bar-codes over than 5m to 10m in a huge warehouse, for instance. In this case, you need to extend the range of bar-code to be read. 

Usually, many normal bar-codes(we can call them standard type) can be read within 1m(it depends on the size and density of the codes). If you need longer distance, you need a long-range scanner. Always, however, you need to check your budget. A long range scanner is much more expensive than a normal one, usually cannot read the codes at near distance, and needs more power.    

Just notice that there are some bar-code modules which can read over than 10m.

On the next post, I will tell you the types of bar-codes. See you later~ :)