Emerson Rosemount 3308 Series Reference Manual page 120

Service and troubleshooting
February 2020
Figure 6-2: Threshold Principle
A. The echo peak is below the threshold (dotted line) and is suppressed by the device.
B. This echo peak is interpreted as the product surface, since it is the first peak closest to
C. Threshold
D. Amplitude
E. Distance
Related information
Thresholds
Guidelines for setting the amplitude thresholds
Normally, the amplitude thresholds are automatically set by the transmitter, and no
manual settings are needed. However, due to the properties of the product, it may in rare
cases be necessary to adjust the amplitude thresholds for optimum measurement
performance.
Guidelines for setting the surface threshold
Before changing the Surface Threshold, ensure the product level is at least 20 in. (0.5 m)
from the lower side of the device flange.
• Surface Thresholds should never be set to values less than 4 Cnts.
• Set the Surface Threshold to about ⅓ of the weakest surface echo amplitude in the
measuring range.
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device that is above the surface threshold.
3.0
Reference Manual
00809-0100-4308
Rosemount 3308 Series