Emerson Rosemount 5408 Reference Manual page 100

Service and Troubleshooting
November 2017
(1)
Symptom
Level is stuck in full tank.
Level value drops to a lower value when
product surface is close to antenna.
Measured value jumps to a lower value.
88
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
Multiple products in the tank,
e.g. thin oil layer on top of
water that is sometimes
detected, sometimes not.
Time
Reference Manual
00809-0100-4408, Rev BA
Recommended actions
Use the suppress false echoes function to

manage strong disturbance echoes, see
"Suppress false echoes" on page
Analyze the echo curve and check amplitude

thresholds, see "Set amplitude thresholds" on
page 96.
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" on
page 106.
Increase the Upper Null Zone, see

disturbances at top of tank" on page
Remove the disturbing object.

Move the transmitter to another position. Refer

to Section 3: Mechanical Installation
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" on page
Set Double Surface Handling to Track Upper
Surface or Track Lower Surface, see
surface handling" on page
Service and Troubleshooting
97.
"Handling
106.
for
199.
"Double
201.