Emerson Rosemount 5408 Reference Manual page 102

Service and Troubleshooting
Table 7-6: Incorrect Level Readings
(1)
Symptom
Level is stuck in full tank.
92
(continued)
Possible causes
Disturbing objects in the
tank.
Time
Disturbing objects near the
antenna.
Time
Product build-up on the an-
tenna.
Cone antenna does not ex-
tend below the nozzle.
Recommended actions
• Use the suppress false echoes function
to manage strong disturbance echoes,
see Suppressing false echoes.
• Analyze the echo curve and check am-
plitude thresholds, see
Amplitude thresholds.
• Remove the disturbing object.
• Change alignment of transmitter head
in steps of about 15 degrees, see
Section 3.5.7. After each step, check if
impact of disturbing echoes is de-
creased using the echo curve.
• Put an inclined metal plate on top of
the disturbing object.
• Move the transmitter to another posi-
tion. Refer to Section 3.3
considerations.
• Use the suppress false echoes function
to manage strong disturbance echoes,
see Suppressing false echoes.
• Analyze the echo curve and check am-
plitude thresholds, see
Amplitude thresholds.
• For process seal antenna installed in a
nozzle taller than 10-in. (25 cm), adjust
the pre-configured amplitude thresh-
old, see Section 7.5.1.
• Increase the Upper Null Zone, see
Section 7.5.1.
• Remove the disturbing object.
• Move the transmitter to another posi-
tion. Refer to Section 3.3
considerations.
• Clean the antenna.
• Use transmitter with air purging con-
nection.
Use the extended cone antenna.
Reference Manual
for installation
for installation