Emerson Rosemount 3308 Series Reference Manual page 119

Reference Manual
00809-0100-4308
6.4.2 Adjusting thresholds
Measurement with the Rosemount 3308A is based on the fact that the radar signal pulses
are reflected by the product surface and the interface between two liquids. Signal
amplitude thresholds are used to separate the measurement signal from disturbing
echoes and noise.
The transmitter uses certain criteria to decide which type of pulse that is detected. For
example, counting from the top of the tank, the first echo found above the Surface
Threshold is considered as the product surface, as illustrated in
further away from the top, although above the Surface Threshold, are ignored. When the
surface echo is found, the next pulse below the product surface and with a signal strength
above the Interface Threshold, is considered as the Interface.
By default, the amplitude thresholds are automatically adjusted to appropriate values in
order to filter out noise and other non-valid measurements from the measurement signal,
as illustrated in
setting the automatically calculated amplitude thresholds. Normally no other threshold
adjustment is needed. But if the transmitter still does not track for example the product
surface, it may be necessary to manually adjust the thresholds.
Reference Manual
• AMS Wireless Configurator: In the dialog box, select Next > to start reading the
echo curve. The reading may take several minutes.
Handheld communicator: Select Echo Curve Graph and follow the on-screen
•
instructions. The reading may take several minutes.
Figure 6-1: Echo Curve Plot in AMS Wireless Configurator
A
A. Reference Peak
B. Product Surface Peak
C. Interface Peak
Figure 6-2. The configured Upper Product Dielectric Constant is used for
C
B
Service and troubleshooting
February 2020
Figure 6-2. Other pulses
119