Emerson 3051S Specifikace stáhnout pdf (Strana 111)

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

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