12
Reference Manual
00809-0100-4026, Rev HA
Section 2: Transmitter Overview
November 2014
Transmitter Overview
2.4 Process characteristics
Dielectric constant
A key parameter for measurement performance is reflectivity. A high dielectric constant of the
media provides better reflection and enables a longer measuring range.
Foam
Rosemount 5400 Series Radar Transmitter measurement in foamy applications depends on the
foam properties; light and airy or dense and heavy, high or low dielectrics, etc. If the foam is
conductive and creamy, the transmitter may measure the surface of the foam. If the foam is less
conductive, the microwaves may penetrate the foam and measure the liquid surface.
Turbulence
A calm surface gives better reflection than a turbulent surface. For turbulent applications, the
maximum range of the radar transmitters is reduced. The range depends on the frequency, the
antenna size, the dielectric of the material, and the degree of turbulence. Consult Tables 2-2 and
2-3 on page 16 for the expected maximum range with the variables listed.
Temperature/pressure/density and vapor
Temperature, pressure, product density, and vapor generally have no impact on measurements.
Condensation
For applications where heavy condensation and vapors may occur, the low frequency version
Rosemount 5401 is recommended.
Tank characteristics
The conditions inside the tank have a significant impact on measurement performance. For
more information see “Vessel characteristics” on page 35.
Solid surface
The surface of solid materials is rarely flat or horizontal. The angle of repose, or surface
inclination, will change as the vessel fills and empties. There is often a lot of dust during the fill
cycle. The dielectric value of many solids is fairly low. See Table 2-1 on page 2-13 for common
solids characteristics.
For solids applications, the high frequency version Rosemount 5402 with 4 inch cone antenna is
available.
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