Emerson Rosemount 3051S Series, Reference Manual

Page: 111 / 240

Reference Manual
00809-0100-4801, Rev FA
October 2010
7-7
Rosemount 3051S Series
Figure 7-5. Simplified SPM
flowchart
Further detail of the operation of the SPM diagnostic is shown in the
Figure 7-5 flowchart. This is a simplified version showing operation using the
default values. While SPM continuously calculates the mean, standard
deviation, and coefficient of variation values, the learning and decision
modules must be turned on to operate. Once enabled, SPM enters the
learning/verification mode and the status will be “Learning”. The baseline
statistical values are calculated over a period of time controlled by the user
(Learning/Monitoring Period; default is 3 minutes). A check is performed to
make sure that the process has a sufficiently high noise or variability level
(above the low level of internal noise inherent in the transmitter itself). If the
level is too low, the diagnostic will continue to calculate baseline values until
the criteria is satisfied (or turned off). 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 change to “Monitoring” status. If the process is unstable, the
diagnostic will continue to verify until stability is achieved. The stability criteria
are also user defined.
Learning/Verifying
Monitoring
User Initiatives
Compute mean,
std. dev. for
3 min.
Sufficient
Noise?
Compute 2nd
mean, std. dev.
for 3 min.
System
Stable?
System
Stable?
“Insufficient
Dynamics”
Change Status
Compute mean (X)
and std. dev. ( )

Decrease in
> 60%?

“Low Variation
Detected”
“High Variation
Detected”
Increase in
> 60%?

Yes
Yes
Yes
Yes
Yes
No
No
No
No
No