Siemens U3585-J-Z125-8-76 1 manual Accuracy of the SM2 data, Causes of inaccuracies

Notes on SM2 operation Accuracy of the SM2 data

6.2 Accuracy of the SM2 data

This section indicates the major factors affecting the accuracy of the data supplied by SM2 or SM2R1. The accuracy of some particularly important variables is also discussed.

Inaccuracies resulting from rounding problems are not considered here.

6.2.1 Causes of inaccuracies

Like all software monitors, SM2 runs under the system to be monitored and thus requires certain resources for its own operation; therefore, strictly speaking, it modifies the system to be monitored. However, this influence is small and can generally be disregarded. For a description of system utilization, see section 7.1.

Inaccuracies resulting from marginal problems

Ideally, the SM2 activities during monitoring activation and deactivation, during the taking of samples and at the end of a monitoring cycle operand, should take no time at all. This being impossible, certain inaccuracies result. However, this effect is minimal and decreases in direct proportion to the number of actions that have to be performed at any given time (small number of tasks, devices etc. to be monitored).

Inaccuracies resulting from classification

Some SM2 values are gathered on a system-global basis, on a category-specific basis, and/or on a task-specific basis. For category-specific data, SM2 uses the category assignment that is valid at the time the data is collected (sample or event). However, SM2 does not recognize category switches for the TASK monitoring program. This is why comparisons between task data accumulated by category and category-specific SM2 data may lead to interpretation errors.

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