Emerson Rosemount 5408 Reference Manual page 108

Service and Troubleshooting
November 2017
Set amplitude thresholds
The amplitude thresholds are used to filter out noise and disturbing echoes from the product surface
echo. The transmitter uses certain criteria to decide which type of echo peak that is detected. Only
echoes above the amplitude threshold might be considered the product surface. The amplitude
threshold can either be set to a constant value, or split into sections as defined by up to 10 anchor points.
If necessary, a customized amplitude threshold section can for instance be used to remove the influence
from the tank nozzle, or disturbances close to the tank bottom. Additionally, it might be needed in areas
where there are occasionally strong echoes present, for instance due to wide mixer blades. Suppressing
false echoes may not be sufficient in those areas.
Note
Do not create a customized amplitude threshold section around echoes which are already registered as
false echoes.
General recommendations
Use the following best practices to apply custom threshold adjustments:
Generally, set amplitude threshold to about 10% of surface echo amplitude.

Do not set the amplitude threshold to less than 150 mV (50 mV for solids measurements)

Procedure
It is recommended to adjust thresholds using Rosemount Radar Master Plus.
To adjust the threshold value:
1. In Rosemount Radar Master Plus, under Service Tools, select Echo Curve.
2. In the echo curve, drag the amplitude threshold point left or right, or type the desired value
(Figure
3. Select Save.
Figure 7-4. Amplitude Threshold Point
A. Amplitude threshold point
1. If required in solids applications with weak surface echoes, the amplitude threshold can be set down to 50 mV, as long as it is greater than the
disturbance echoes.
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7-4).
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Service and Troubleshooting