Emerson 3051S Dokumentacja Pobierz pdf (Strona 83)

Reference Manual

00809-0200-4801, Rev CA

July 2010

6-5

Rosemount 3051S

Figure 6-4. Flow Chart of 3051S

FF Statistical Process

Monitoring

Further detail of the operation of the SPM diagnostic is shown in the

Figure 6-4 flowchart. This is a simplified version showing operation using the

default values. After configuration, SPM calculates mean and standard

deviation, used in both the learning and the monitoring modes. Once enabled,

SPM enters the learning/verification mode. The baseline mean and standard

deviation are calculated over a period of time controlled by the user (SPM

Monitoring Cycle; default is 15 minutes). The status will be “Learning”. A

second set of values is calculated and compared to the original set to verify

that the measured process is stable and repeatable. During this period, the

status will change to “Verifying”. If the process is stable, the diagnostic will use

the last set of values as baseline values and move to “Monitoring” status. If

the process is unstable, the diagnostic will continue to verify until stability is

achieved.

In the “Monitoring” mode, new mean and standard deviation values are

continuously calculated, with new values available every few seconds. The

mean value is compared to the baseline mean value, and the standard

deviation is compared to the baseline standard deviation value. If either the

mean or the standard deviation has changed more than user-defined

sensitivity settings, an alert is generated via F

OUNDATION fieldbus. The alert

may indicate a change in the process, equipment, or transmitter installation.

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Emerson 3051S Dokumentacja Strona 83