Siemens CPU 313C Hardware And Installation Manual page 215

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The notes below apply independent of the type or manufacturer of the electronic
control.
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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.
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
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