Emerson Guided Wave Radar Level and Interface Transmitters 3300 - Manual (Page 13)

Reference Manual
00809-0100-4811, Rev CA
February 2006
Rosemount 3300 Series
www.rosemount.com
Section 2 Transmitter Overview
Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-2
Components of the Transmitter . . . . . . . . . . . . . . . . . . . . page 2-4
System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-5
Probe Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-6
Process Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-8
Vessel Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-11
THEORY OF OPERATION The Rosemount 3300 Series Radar Transmitter is a smart, two-wire
continuous level transmitter that is based on Time Domain Reflectometry
(TDR) principles. Low power nano-second-pulses are guided along a probe
immersed in the process media. When a pulse reaches the surface of the
material it is measuring, part of the energy is reflected back to the transmitter,
and the time difference between the generated and reflected pulse is
converted into a distance from which the total level or interface level is
calculated (see below).
The reflectivity of the product is a key parameter for measurement
performance. A high dielectric constant of the media gives better reflection
and a longer measuring range. A calm surface gives better reflection than a
turbulent surface.
Figure 2-1. Measurement
Principle.
Time
TDR_PRINCIP
L
ES
Reference Pulse
Level
Interface Level
Signal Amplitude