Emerson Rosemount 5408 Reference Manual page 109

Reference Manual
00809-0100-4408
Table 7-6: Incorrect Level Readings
(1)
Symptom
Level is stuck in full tank.
Level value drops to a lower value when
product surface is close to antenna.
Rosemount 5408 and 5408:SIS Level Transmitters
(continued)
Possible causes
Disturbing objects near the
antenna.
Time
Product build-up on the
antenna.
Cone antenna does not
extend below the nozzle.
Product surface is within the
Upper Null Zone and a
disturbance echo is
interpreted as the product
surface.
Time
Service and troubleshooting
Recommended actions
• Use the suppress false echoes function
to manage strong disturbance echoes,
see Suppressing false echoes.
• Analyze the echo curve and check
amplitude thresholds, see
thresholds.
• For process seal antenna installed in a
nozzle taller than 10-in. (25 cm), adjust
the pre-configured amplitude
threshold, see Handling disturbances at
top of tank.
• Increase the Upper Null Zone, see
Handling disturbances at top of
• Remove the disturbing object.
• Move the transmitter to another
position. Refer to Installation
considerations for installation
considerations.
• Clean the antenna.
• Use transmitter with air purging
connection.
Use the extended cone antenna.
Check the setting of the Upper Null Zone,
see Upper null zone.
February 2020
Amplitude
tank.
109