Emerson Rosemount 3051 CF Series, Reference Manual

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SPM_Active
The SPM_Active parameter starts the statistical process monitoring when Enabled.
Disabled (default) turns the diagnostic monitoring off. You must set this parameter to
Disabled for configuration. Only set it to Enabled after fully configuring the SPM. When
enabling SPM, you may select one of two options:
Enabled with 1st-order HP filter
This 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 without 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.
7.5.3 Configuration of alerts
In order to have SPM generate a NE107 or Plantweb
®
alert, you must configure the alert
limits 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; typical values
for high variation limit are 40 percent change for high sensitivity, 60% change for medium
sensitivity, and 80 percent change for low sensitivity.
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_Variation_Limit is
0
, then SPM does not detect an increase in
standard deviation.
Figure 7-6 illustrates an example of the standard deviation, with its baseline value and alert
limits. During the monitoring phase, the SPM will continuously evaluate the standard
deviation and compare it against the baseline value. SPM detects an alert 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
Advanced pressure diagnostics Reference Manual
July 2020 00809-0100-4774
126 Rosemount 3051