1.Storage capacity
Storage capacity refers to the capacity of the user program memory. The capacity of the user program memory is large enough to prepare complex programs. Generally speaking, the user memory capacity of small PLC is several thousand words, while the user memory capacity of large machines is several tens of thousands of words.
2. I/O points
Input/Output (I/O) points is the total number of input signals and output signals that can be accepted by the PLC, is an important indicator of the performance of the PLC. the more I/O points, the more external input devices and output devices can be connected, the larger the scale of control.
3. Scanning speed
Scan speed refers to the speed of the PLC to implement the user program, is an important indicator to measure the performance of the PLC. PLC user manual generally gives the time used to implement each instruction, you can compare the time used to perform the same operation by a variety of PLC to measure the speed of scanning.
4. The function of the instruction and the number of
The strength of the function of the instruction, the number of how much is also an important indicator of the performance of the PLC. The stronger the function of the programming instructions, the more the number, the stronger the processing power and control ability of the PLC, the simpler and more convenient user programming, the easier it is to complete complex control tasks.
5. The type and number of internal components
In the preparation of PLC program, a large number of internal components are needed to store variables, intermediate results, hold data, timing and counting, module settings and various flag bits and other information. The more types and numbers of these components, the stronger the ability of the PLC to store and process a variety of information.
6. Special Function Unit
The number of types of special function units and the strength of the function is an important indicator to measure the PLC products. In recent years, PLC manufacturers attach great importance to the development of special function units, special function units are increasing, the function is getting stronger and stronger, so that the PLC control function is expanding
7. Expandability
PLC scalability includes the expansion of the number of I/O points, the expansion of storage capacity, the expansion of networking functions, the expansion of various functional modules, etc.. In the selection of PLC, it is often necessary to consider the scalability of PLC.