Emerson Rosemount 3051S Series Reference Manual page 100

Advanced Pressure Diagnostics
October 2016
2. Sufficient variation?
During the Learning and the Verify modes, the PIL checks that the noise level (e.g. the standard deviation)
is high enough for reliable detection of plugged impulse lines. If the noise level is too low, the status goes
to "Insufficient Dynamics", and the PIL stops. PIL will not resume learning again until a "Relearn"
command is given.
3. Verification phase
PIL collects the pressure values for an additional five minutes (or same length as learning period) and
computes a second mean and standard deviation. During this phase, the PIL status is "Verifying".
4. Steady process?
At the end of the 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 one minute and computes the mean and
the standard deviation.
Note
The length of this detection period is user-adjustable, with one minute as the default value.
7. Relearn required?
At the end of the detection phase, 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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Reference Manual
00809-0200-4801, Rev DA
Advanced Pressure Diagnostics