Emerson Rosemount 3051S Series, Reference Manual

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Reference Manual
00809-0100-4801, Rev FA
October 2010
Rosemount 3051S Series
7-20
POWER ADVISORY
Introduction
The Power Advisory diagnostic provides a means to detect issues that may
jeopardize the integrity of the electrical loop. Some examples are: water
entering the wiring compartment and makes contact with the terminals, an
unstable power supply nearing end of life, or heavy corrosion on the
terminals.
This technology is based on the premise that once a transmitter is installed
and powered up, the electrical loop has a baseline characteristic that reflects
the proper installation. If the transmitter terminal voltage deviates from the
baseline and outside the user configured threshold, the 3051S can generate a
HART alert or analog alarm.
To make use of this diagnostic, the user must first create a baseline
characteristic for the electrical loop after the transmitter has been installed.
The loop is automatically characterized with the push of a button. This creates
a linear relationship for expected terminal voltage values along the operating
region from 4 – 20 mA, see Figure 7-16.
Figure 7-16. Baseline operating
region
SPM diagnostic will not leave verifying
mode Process is unstable. Increase learning sensitivity
checks (Verification Criteria screen). If this does
not correct the issue, increase the learning
verification period to match or exceed the cycle
time of the instability of the process. If maximum
time does not correct the problem, process is not
a candidate for SPM diagnostic. Correct stability
issue or turn off diagnostic.
SPM diagnostic does not detect a known
condition With the condition present, but the process
operating, go to the SPM Status or Operational
Values screen and note the current statistical
values and compare to the baseline and
threshold values. Adjust the sensitivity values
until a trip of the diagnostic occurs.
SPM diagnostic indicates “High Variation
Detected” when no diagnostic event has
occurred The most likely cause is a fast change in the
value of the process variable. Direction of the
change is not important. Increase the
learning/monitoring period to better filter out
increases in standard deviation.
Table 7-7. Possible SPM issues and resolutions
SPM Diagnostic Issue Action
Volts
4 mA 20 mA
Output Current
T
e
rminal V
o
lt
age