Spm Overview - Emerson Rosemount 3051S Series Reference Manual

Rosemount 3051S Series

SPM Overview

Figure 7-3. Block diagram of the
Statistical Process Monitoring
diagnostic resident in 3051S
HART Diagnostics Transmitter
7-4
The device can provide the statistical information to the user in two ways.
First, the statistical parameters can be made available to the host system
directly via HART communication protocol or HART to other protocol
converters. Once available, the system may make use of these statistical
parameters to indicate or detect a change in process conditions. In the
simplest example, the statistical values may be stored in the DCS historian. If
a process upset or equipment problem occurs, these values can be examined
to determine if changes in the values foreshadowed or indicated the process
upset. The statistical values can then be made available to the operator
directly, or made available to alarm or alert software.
Second, the device has internal software that can be used to baseline the
process noise or signature via a learning process. Once the learning process
is completed, the device itself can detect significant changes in the noise or
variation, and communicate an alarm via the 4 – 20 mA output and/or alert via
HART. Typical applications are detection of plugged impulse lines, change in
fluid composition, or equipment related problems.
A block diagram of the Statistical Process Monitoring (SPM) diagnostic is
shown in Figure 7-3. The pressure process variable is input to a module
where basic high pass filtering is performed on the pressure signal. The mean
(or average) is calculated on the unfiltered pressure signal, the standard
deviation calculated from the filtered pressure signal. These statistical values
are available via HART and handheld communication devices like the 375
Field Communicator or asset management software like Emerson Process
™
Management's AMS Device Manager. The values can also be assigned as
secondary variables from the device for 4-20 mA communication to the user
through other devices like the Rosemount 333 HART Tri-loop (see page 7-23
for more information).
Statistical
Process
Calculations
Variable
Module
Resident in Transmitter
Reference Manual
00809-0100-4801, Rev EA
Learning
Module
Baseline
Values
Decision
Module
Statistical Parameters
August 2010
Standard
Outputs
(4-20 mA/HART)
Control
Inputs
Alerts/
Alarms
Outputs