This paper discusses high building preventing thunder earthing design and its importance from the requirement of high building preventing thunder, reinforcing steel bar concrete base earthing body and step voltage disposing.
This text analyses that earth noise and electromagnetic reasons and countermeasures penetrated emerge in the printed circuit board signal earth design of PCB. Adopt single some earth, multipoint earthing , mix earth , simulation circuit earth , digital circuit earth introduce PCB printed circuit board earth mentality of designing , design method , skill.
Firstly four ways of power supply system protection and power supply design of general PLC system are concretely put forward. Then,two kinds of I/O blocks power design in 24VDC and 220VAC are given in the power supply design of I/O blocks. Finally attentive problems in earth design and the choice of earth resistances are mainly analysed.