Emerson 3051S Especificações descarregar pdf (Página 102)

Reference Manual

00809-0200-4801, Rev CA

July 2010

Rosemount 3051S

6-24

4. Steady Process?

At the end of the 5-minute verification phase, the PIL compares the last

mean and standard deviation against the previous mean and standard

deviation to determine if the process is at a steady state. If the process is

at a steady-state, then the PIL moves into Detection phase. If not, then

PIL repeats the Verification Phase

5. Establish Baseline

At the end of the Verification Phase, if the process has been determined

to be at a steady state, the last mean and standard deviation are taken to

be the “Baseline” values, representative of the normal process operating

condition.

6. Detection Phase

During the Detection Phase, the PIL collects pressure data for 1 minute

and computes the mean and the standard deviation.

NOTE:

The length of this “Detection Period” is user-adjustable, with 1-minute as the

default value.

7. Relearn Required?

At the end of the 1-minute, PIL first compares the current mean with the

baseline mean. If the two differ significantly, then the PIL goes back into

the Learning Phase, because the process conditions have changed too

much for a reliable detection of a plugged impulse line.

8. Compare Standard Deviations

If no relearn is required, the PIL compares the current standard deviation

against the baseline standard deviation to determine if a plugged

impulse line is detected. For all sensor types, the PIL checks if the

standard deviation has decreased below a lower limit. For DP sensors,

the PIL also checks if the standard deviation has increased above an

upper limit. If either of these limits is exceeded, the status changes to

“Lines Plugged” and the PIL stops, and will not resume again until a

“Relearn” command is given. If a plugged impulse line is not detected,

the status is “OK” and the Detection Phase is repeated.

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Emerson 3051S Especificações Página 102