1.7: PLC product application language

The PLC market can be segmented into five groups:

1. Micro PLCs

2. Small PLCs

3. Medium PLCs

4. Large PLCs

5. Very large PLCs

Figure 1-9 graphically illustrates programmable controller product ranges.

Micro PLCS are used in applications controlling up to 32 input and output devices, 20 or less I/O being the norm. The micros are followed by the small PLC category, which controls 32 to 128 I/O. The medium (64 to 1024 I/O), large (512 to 4096I/O), and very large (2048 to 8192I/O) PLCs complete the segmentation

The A, B, C overlapping areas in the figure reflect enhancement adding options, of the standard features of the PLCS within a particular segment. These options allow a product to be closely matched to the application without having to purchase of larger unit. The differences between PLCs in overlapping areas include I/O count, memory size, programming language, software functions, and other factors .an understanding of the plc product ranges and their characteristic will allow the user to properly identify the controller that will satisfy a particular application.