Emerson 3051S Dokumentacja Pobierz pdf (Strona 86)

Reference Manual

00809-0200-4801, Rev CA

July 2010

Rosemount 3051S

6-8

Figure 6-5. Effect of the SPM

Monitoring Cycle on the

Statistical Values

SPM#_User_Command

Select “Learn” after all the parameters have been configured to begin the

Learning Phase. The monitoring phase will start automatically after the

learning process is complete. Select “Quit” to stop the SPM. “Detect” may be

selected to return to the monitoring phase.

SPM_Active

The SPM_Active parameter starts the Statistical Process Monitoring when

“Enabled”. “Disabled” (default) turns the diagnostic monitoring off. Must be set

to “Disabled” for configuration. Only set to “Enabled” after fully configuring the

SPM. When Enabling SPM, you may select one of two options:

Enabled with 1st-Order HP Filter

Applies a high-pass filter to the pressure measurement prior to calculating

standard deviation. This removes the effect of slow or gradual process

changes from the standard deviation calculation while preserving the

higher-frequency process fluctuations. Using the high-pass filter reduces

the likelihood of generating a false detection if there is a normal process or

setpoint change. For most diagnostics applications, you will want to use

the filter.

Enabled w/o Filter

This enables SPM without applying the high-pass filter. Without the filter,

changes in the mean of the process variable will cause an increase in the

standard deviation. Use this option only if there are very slow process

changes (e.g. an oscillation with a long period), which you wish to monitor

using the standard deviation.

Configuration of Alerts In order to have SPM generate a PlantWeb alert, the alert limits must be

configured on the mean and/or standard deviation. The three alert limits

available are:

SPM#_Mean_Lim

Upper and lower limits for detecting a Mean Change

SPM#_High_Variation_Lim

Upper limit on standard deviation for detecting a High Variation condition

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Emerson 3051S Dokumentacja Strona 86