Emerson 8700 Series, Reference Manual

Page: 60 / 136

Reference Manual
00809-0100-4793, Rev CA
August 2004
Rosemount 8742C
5-8
Electrode Signal
Fault Detected The flow signal has been compromised. The process
variable is likely reading less than expected.
• Remove any moisture or contamination in the flowtube
terminal block or, if applicable, the sealed electrode
compartments.
WARNING: The electrode compartment may contain line
pressure. Removing the cover before depressurizing may
result in death or serious injury.
• Perform flowtube electrical resistance tests. Confirm the
resistance reading between coil ground (ground symbol)
and coil (1 or 2) is infinity. Confirm the resistance reading
between electrode ground (17) and an electrode (18 or
19) is greater than 2 kohms and rises. For more detailed
information, consult the flowtube product manual.
• Verify flowtube is electrically connected to the process
with grounding electrode, grounding rings with grounding
straps, or lining protector with grounding straps.
• Verify transmitter electronics with Rosemount 8714
reference standard. The dial on the 8714 should be set
at 9.1 m/s (30 ft/s). The transmitter should
(1000015010000000) and 5 Hz coil drive frequency.
• Properly connect the wiring between the flowtube and
the transmitter on the flowtube. Corresponding terminal
block numbers in the flowtube and transmitter must be
connected.
To turn off electrode signal fault detection, go to the
diagnostic screen in the transducer block properties.
Grounding/ Wiring
Fault The transmitter detected high levels of 50/60 Hz noise
caused by improper wiring or poor process grounding.
• Connect ground rings, grounding electrode, lining
protector, or grounding straps. Grounding diagrams are
included in the flowtube product manual.
• verify flowtube is full.
• Verify wiring between flowtube and transmitter is
prepared properly. Shielding should be stripped back
less than 2.5 cm (1 in).
• Use separate shielded twisted pairs for wiring between
flowtube and transmitter.
• Properly connect the wiring between the flowtube and
the transmitter on the flowtube. Corresponding terminal
block numbers in the flowtube and transmitter must be
connected.
To turn off grounding/ wiring diagnostic, go to the diagnostic
screen in the transducer block properties.
Electronics Failure The electronics board stack has failed.
• Replace the electronics board stack or complete
transmitter.
Electronics Trim
Failure The transmitter calibration process has been
interrupted or failed. No internal calibration parameters
have been modified.
• If electronics trim performed inadvertently, cycle
transmitter power to clear message.
• Verify transmitter electronics with Rosemount 8714
reference standard. The dial on the 8714 should be set
at 9.1 m/s (30 ft/s). The transmitter should
(10000015010000000) and 5 Hz coil drive frequency.
Auto Zero Failure The Auto Zero process has been interrupted or failed.
No internal Auto Zero parameters have been modified.
• If Auto Zero performed inadvertently, cycle transmitter
power to clear message.
• Repeat Auto Zero process with a full pipe and no flow.
• Verify transmitter electronics with Rosemount 8714
reference standard. The dial on the 8714 should be set
at 9.1 m/s (30 ft/s). The transmitter should
(10000015010000000) and 5 Hz coil drive frequency.
Table 5-2. Triggered Diagnostics
Symptom Probable Cause Corrective Action