Alert Configuration; Spm Operations - Emerson Rosemount 3051S Series Reference Manual

Advanced Pressure Diagnostics
October 2016
6.3.4

Alert configuration

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
SPM#_Low_Dynamics_Lim
Lower limit on standard deviation for detecting a Low Dynamics condition (must be specified as a
negative number)
All of these limits are specified as a percent change in the statistical value from its baseline. If a limit is set
to 0 (the default setting) then the corresponding diagnostic is disabled. For example, if SPM#_High_Vari-
ation_Limit is 0, then SPM# does not detect an increase in standard deviation.
Figure 6-6
the monitoring phase, the SPM will continuously evaluate the standard deviation and compare it against
the baseline value. An alert will be detected if the standard deviation either goes above the upper alert
limit, or below the lower alert limit.
In general, a higher value in any of these limits leads to the SPM diagnostic being less sensitive, because a
greater change in mean or standard deviation is needed to exceed the limit. A lower value makes the
diagnostic more sensitive, and could potentially lead to false detections.
Figure 6-6. Example Alerts for Standard Deviation
6.3.5

SPM operations

During operation, the following values are updated for each SPM Block (e.g. SPM1-SPM4)
SPM#_Baseline_Mean
Baseline mean (calculated average) of the process variable, determined during the Learning/Verification
process, and representing the normal operating condition
SPM#_Mean
Current Mean of the process variable
76
illustrates an example of the standard deviation, with its baseline value and alert limits. During
Reference Manual
00809-0200-4801, Rev DA
Advanced Pressure Diagnostics