Wednesday, November 12, 2014

Guided-wave Radar Level Sensing

Time domain reflectometry for guided-wave radar level
 Guided-wave Radar Level Sensing based
upon Time domain reflectometry (TDR)
(image courtesy of Wikipedia)
Guided-wave radar (GWR) uses a probe immersed in the process media to guide high-frequency electromagnetic waves into the media being measured, and then analyzes the reflected energy to determine level.

GWR is based upon the phenomena of time domain reflectometry (TDR). TDR begins with the initiation of a low-energy electromagnetic pulse of energy into a process through a probe. The subsequent measurement of the energy reflected from the surface of the medium being measured is communicated from the probe to the instrument electronics. By analyzing the reflected waveform, a calculation of level can be made. The instrument then correlates the waveform information to a continuous, or switched, output signal.

Guided-wave radar level transmitter
Guided-wave radar
level transmitter
(courtesy of King Gage)
Guided-wave radar isn’t dependent or subject to the process media properties it is sensing, unlike other electronic level sensing technologies, and can be used for both liquids and solids.

GWR is best suited for the following types of applications:

  • Processes undergoing turbulence or changing density or viscosity.
  • Moving, agitated, foaming, vaporous or circulating surfaces.
  • Processes with higher temperatures and pressures.
  • Sticky or gummy processes, such as oil, paint, rubber or tar.
  • Fine particulate processes such as carbon black, salt, or grain.

One significant advantage to guided-wave radar is that build up on the probe has no effect on the accuracy. While this might be counter-intuitive, the GWR technology “ignores” the relatively insignificant amount of probe build up. This is because the signal returned from the electromagnetic pulse corresponding from the actual process media level is always larger than any reflected signal from build up, which makes it easy for the instrument to determine the difference.

For more information on guided-wave radar level controls, contact:

Mountain States Engineering and Controls
1520 Iris Street
Lakewood, CO 80215
303.232.4100 Phone
303.232.4900 Fax