If you work in the Automation Industry, you will know that automation equipment is very expensive. And many a time, especially for small applications, you simply cannot justify the use of very expensive equipment.
This is where the Arduino comes in!
The Arduino development board allows you to create very simple, but very powerful, Modbus master or slave devices through the use of relatively simple "C" programming. With the Arduino, you have full custom control over the program design allowing you to create very lean and very efficient devices for very specific purposes.