Siemens Simatic S7-300, Hardware And Installation Manual, Page: 218 / 242

Appendix
S7-300 Programmable Controller Hardware and Installation
11-30
A5E00105492-01
11.4 Safety of electronic control equipment
Introduction
The notes below apply independent of the type or manufacturer of the electronic
control.
Reliability
Maximum reliability of SIMATIC devices and components is achieved by
implementing extensive and cost-effective measures during development and
manufacture:
This includes the following:
•
Use of high-quality components;
•
Worst-case design of all circuits;
•
Systematic and computer-aided testing of all components;
•
Burn-in of all large-scale integrated circuits (e.g. processors, memory, etc.);
•
Measures preventing static charge when handling MOS ICs;
•
Visual checks at different stages of manufacture;
•
Continuous heat-run test at elevated ambient temperature over a period of
several days;
•
Careful computer-controlled final testing;
•
Statistical evaluation of all returned systems and components to enable the
immediate initiation of suitable corrective measures;
•
Monitoring of major control components, using on-line tests (watchdog for the
CPU, etc.).
These measures are referred to in safety technology as basic measures. They
prevent or rectify a large proportion of possible faults.