Troubleshooting guide

Reference Manual
00809-0100-4308, Rev BA
Section 2: Transmitter Overview
December 2014
3Transmitter Overview
Section 2 Transmitter Overview
Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3
Emerson's Smart Wireless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 3308 Series is the first true wireless level transmitter that is based on the Time
Domain 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 Figure 2-1).
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
Time
Reference Peak
Signal Amplitude
Tank Height
Product Level
Upper Reference Point
Zero Reference Point
Interface
Level
Probe
Length
Product Surface
Peak
Interface Peak