Theory Of Operation - Emerson Rosemount 3308A Reference Manual

Reference Manual
00809-0100-4308, Rev BB
Section 2
Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3
Wireless by Emerson™ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 6
Application characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 6
Application examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8
Components of the transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 9
Probe selection guide for the Rosemount 3308 Series Transmitter . . . . . . . . . . . . . . . . . . . . . . page 10
2.1

Theory of operation

The Rosemount
Reflectometry (TDR) principle. Low power nano-second-pulses are guided along a probe submerged 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
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.
Figure 2-1. Guided Wave Radar Operating Principle
Reference Peak
Transmitter Overview
Transmitter Overview
™
3308 Series is the first true wireless level transmitter that is based on the Time Domain
Signal Amplitude
Product Surface
Peak
Product Level
Interface Peak
Time
Interface
Level
Transmitter Overview
October 2016
Figure 2-1).
Upper Reference Point
Probe Tank Height
Length
Zero Reference Point
3