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Reference Manual

00809-0100-4811, Rev DA

Section 2: Transmitter Overview

January 2015

Transmitter Overview

2.4 Process characteristics

The Rosemount 3300 Series has high sensitivity due to its advanced signal processing and high

signal to noise ratio, which makes it able to handle various disturbances. However, the following

circumstances should be considered before mounting the transmitter.

2.4.1 Coating

Coating on the probe should be avoided since the sensitivity of the transmitter may be

decreased leading to measurement errors. In viscous or sticky applications, periodic cleaning

may be required.

For viscous or sticky applications, it is important to select a suitable probe. For detailed

information on the maximum recommended viscosity and coating, see Table A-6 on page 131.

Maximum measurement error due to coating is 1-10% depending on probe type, dielectric

constant, coating thickness, and coating height above product surface.

2.4.2 Bridging

Heavy coating that results in product bridging across the two probes for twin lead versions, or

between the pipe and the inner rod for coaxial probes, causes erroneous level readings and must

be prevented. Single lead probes are preferred in this case. If a twin lead probe is required,

regular cleaning may be necessary.

2.4.3 Foam

How well the Rosemount 3300 Series Radar Transmitter measures in foamy applications

depends upon the properties of the foam; light and airy or dense and heavy, high or low

dielectrics, etc. If the foam is conductive and creamy, the transmitter will probably measure the

surface of the foam. If the foam is less conductive, the microwaves will probably penetrate the

foam and measure the liquid surface.

2.4.4 Vapor

In some applications, such as ammonia, there is heavy vapor above the product surface that will

influence the level measurement. The Rosemount 3300 Series Radar Transmitter can be

configured to compensate for the influence of vapor.

2.4.5 Measuring range

The measuring range differs depending on probe type and characteristics of the application.

The values given in Table A-4 on page 128 can be used as a guideline for clean liquids.

The maximum measuring range differs depending on application according to:

 Disturbing objects close to the probe.

 Media with higher dielectric constant (

) give better reflection and allow a longer

measuring range.

 A calm surface gives better reflection than a turbulent surface. For a turbulent surface,

the measuring range might be reduced.

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