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Outlining the working principles of radar level transmitters

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Guided wave radar level transmitters are used to continuously monitor fluid or bulk solid levels in harsh operating conditions. They operate on a similar principle to laser time-of-flight analysis albeit with fewer limitations regarding the gaseous composition of the headspace.

Radar level transmitters use top-down waveguides to generate and direct microwave pulses downwards into a containment vessel. These signals propagate through the headspace due to the low dielectric constant, or relative permittivity (Er), of gas and vapor species. When they reach the discontinuity between the low dielectric headspace and the higher dielectric liquid or solid, these pulses are reflected back to the level transmitter. An integrated timing circuit calculates how long it took for pulses generated at the antennae to return, providing accurate level measurements based on the dielectric characteristics of the measured media.

This operating principle is a form of time-domain reflectometry (TDR), which often uses the magnitude of signals and the shape of reflected waveforms to provide more detailed data regarding the dielectric discontinuity. Innovative radar level transmitters have been equipped with waveform capabilities to provide real-time level measurements in process monitoring applications.

The components of radar level transmitters

Guided wave radar level transmitters are typically equipped with a flexible cable or rigid probe-type antennae engineered from robust corrosion-resistant materials. Stainless steel, Hastelloy, and titanium are often used to engineer the sensor that protrudes into a container from above. In some applications, radar level transmitters can be installed horizontally with sensors adjusted to 90° angles. These components generate and transmit microwave pulses across a highly focused energy path before detecting them after reflection.

The speed of a microwave is typically unaffected by process variables such as pressure, temperature, and density. This, combined with the elimination of beam-spread phenomena due to the confinement of incident radio waves, provides a signal that is as much as twenty times more efficient than through-air radar systems.

These signals are transmitted directly to the electronics module through a radio frequency interference (RFI) filter to reduce background noise and provide reliable output readings. Standard graphical displays show level measurement as a function of liquid height in the containment vessel. Advanced radar level transmitters are equipped with additional digital display capabilities, including waveform screens for real-time level monitoring and built-in diagnostics.

Radar level transmitters from ABB

ABB is one of the world’s leading suppliers of process monitoring equipment for industrial environments. We supply a unique selection of radar level transmitters for liquid level, liquid interface level, and bulk solid level measurements in demanding operating conditions. These include the MT5000, MT51000, and the MT5200.

If you would like any more information about our radar level transmitters, simply find your local contact below. 

 

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