Emerson 3051S Dokumentacja Pobierz pdf (Strona 88)

Reference Manual

00809-0200-4801, Rev CA

July 2010

Rosemount 3051S

6-10

SPM#_StDev

Current Standard Deviation of the process variable

SPM#_StDev_Change

Percent change between the Baseline Standard Deviation and the Current

Standard Deviation

SPM#_Timestamp

Timestamp of the last values and status for the SPM

SPM#_Status

Current state of the SPM Block. Possible values for SPM Status are as

follows:

In most cases, only one of the above SPM status bits will be active at one

time. However, it is possible for “Mean Change Detected” to be active at the

same time as either “High Variation Detected” or “Low Dynamics Detected” is

active.

PlantWeb Alert When any of the SPM detections (Mean Change, High Variation, or Low

Dynamics) is active, a Fieldbus PlantWeb alert in the device “Process

Anomaly Detected (SPM)” will be generated and sent to the host system.

However, note that there is just one SPM PlantWeb alert, and it applies to all

the detections on all four SPM blocks.

Trending Statistical

Values in Control System

SPM Mean and Standard Deviation values may be viewed and/or trended in a

Fieldbus host system through the AI or MAI function blocks.

An Analog Input (AI) block may be used to read either the mean or the

standard deviation from any one of the SPM Blocks. To use the AI block to

trend SPM data, set the CHANNEL parameter to one of the following values:

Status Value Description

Inactive User Command in “Idle”, SPM not Enabled, or the function block is

not scheduled.

Learning Learning has been set in the User Command, and the initial

baseline values are being calculated

Verifying Current baseline values and previous baseline values or being

compared to verify the process is stable.

Monitoring Monitoring the process and no detections are currently active.

Mean Change Detected Alert resulting from the Mean Change exceeding the Threshold

Mean Limit. Can be caused by a set point change, a load change

in the flow, or an obstruction or the removal of an obstruction in the

process.

High Variation Detected Alert resulting from the Stdev Change exceeding the Threshold

High Variation value. This is an indicator of increased dynamics in

the process, and could be caused by increased liquid or gas in the

flow, control or rotational problems, or unstable pressure

fluctuations.

Low Dynamics Detected Alert resulting from the Stdev Change exceeding the Threshold

Low Dynamics value. This is an indicator for a lower flow, or other

change resulting in less turbulence in the flow.

Not Licensed SPM is not currently purchased in this device.

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