Emerson Rosemount 3051CF Series Reference Manual page 125

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7.5.2 Other SPM settings
Additional information on other SPM settings is shown below.
SPM_Bypass_Verification
If this is set to Yes, SPM will skip the verification process and take the first mean and
standard deviation from the learning phase as the baseline mean and standard deviation.
By skipping the verification, the SPM can move into the monitoring phase more quickly.
Only set this parameter set to Yes if you are certain that the process is at a steady-state at
the time you start the learning phase. The default (and recommended) setting is No.
SPM_Monitoring_Cycle
This is the length of the sample window over which mean and standard deviation are
computed. A shorter sample window means that the statistical values will respond faster
when there are process changes, but there is also a greater chance of generating false
detections. A longer sample window means that mean and standard deviation will take
longer to respond when there is a process change. The default value is 15 minutes. For
most applications, a monitoring cycle ranging from 1 to 10 minutes is appropriate. The
allowable range is 1 to 1440 minutes.
Figure 7-5
Notice how with a shorter sampling window there is more variation (e.g., the plot looks
noisier) in the trend. With the longer sampling window, the trend looks smoother,
because the SPM uses process data averaged over a longer period of time.
Figure 7-5: Effect of SPM Monitoring Cycle on Statistical Values
SPM_User_Command
Select Learn after all the parameters have been configured to begin the Learning Phase.
The monitoring phase starts automatically after the learning process is complete. Select
Quit to stop the SPM. Select Detect to return to the monitoring phase.
Reference Manual
illustrates the effect of the SPM monitoring cycle on the statistical calculations.
Advanced pressure diagnostics
July 2020
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