Guided wave radar transmitters are widely used across different industries. These devices with their simple installation and trouble-free operations help industrial companies save time and money. They are ideal for a large number of process applications ranging from simple to complex.
How Do Guided Wave Radar Transmitters Work?
Guided wave radar transmitters rely on microwave pulses. Since microwaves are not affected by dust, pressure, temperature variations, and viscosity, this type of transmitter produces highly accurate results.
A low-energy microwave pulse is sent down a probe, and a part of it is reflected back when the pulse hits the process media. The liquid level is directly proportional to the time-domain reflectometry. The time when the pulse is launched and received back is measured to determine the distance from the surface of the media.
Types of Guided Wave Radar Level Transmitters
Guided wave radar level transmitters are available in different probe configurations. Selecting the right probe is important for successful implementation of the device. While manufacturers offer a range of guided wave radars, most are derived from the three basic probe configurations: single element, twin element, and coaxial.
Single element probe — The single element probe is the most widely used and least efficient device. The device is popular since it is more resistant to the coating of the liquid.
Twin element probe — The twin element probe is a good, general purpose probe that is generally used in long-range applications. They are ideal in situations where flexible probes are important for successful reading.
Coaxial probe — The coaxial probe configuration is the most efficient guided wave radar level transmitters. The probes are used in more challenging low-dielectric applications.
Benefits of Guided Wave Radar Level Transmitters
|Dielectric Constant and Reflectivity - Guided WaveRadar (GWR)|
(Courtesy of Schneider Electric Foxboro)
Guided wave radar level transmitters provide a range of benefits in different applications. The concentration of the measuring signal is strong and clean. This is due to the narrow path of the signal propagation that reduces the chances of impact by stray signals due to obstacles or construction elements inside the tank.
Another benefit of guided wave radar level transmitters is that they are easy to install. No mounting holes are required to install the device. This results in cost savings for the organization. The waveguide can be formed to follow the tank’s contours or mounted at an angle.
The device is ideal in situations where an interface measurement is required. The measuring signals can penetrate the medium deeply, resulting in more accurate results. The waveguide technology is suitable for applications where the medium is subjected to heavy vapors, foam, and dust.
Guided wave instruments can detect changes in dielectric consents on the boundary of a property. The device can be configured to detect level at both the top and the bottom of a layer of emulsion.
Industrial Application of Guided Wave Radar
Guided wave radar level transmitters are increasingly being used in process industries. The sensors are used in situations that previously employed ultrasonic, hydrostatics, and capacitance. The accuracy specification of the basic model range is up to ±5mm, while the accuracy of the advanced models is up to ±2mm.
The device is generally used in industries to take level readings. The readings are used for local indication and visualization in control systems.
Moreover, guided wave radar level transmitters are also used for managing liquid inventory, determining safety limits, dry run protection, and leak detection. Other applications of guided wave radar level transmitters include communicating low limits to suppliers, automated ordering systems, and streamlining the logistics process.
Guided radar level measurement is also suitable for bulk solids. The surface type is not restricted to liquids since the reflected waves are guided easily through any medium. Foam formation and turbulent liquid surfaces and different angled surfaces (as is the case with bulk solids) don’t influence the accuracy of the reading.
Selection of Guided Wave Radar Level Transmitters
Selection of guided wave radar level transmitters should be based on the requirements of the task. Generally, the rigid single element probe configuration is ideal for angled installations for flowing liquids. The dual flexible wire probe is suitable for most other common applications.
A coaxial probe configuration is recommended for liquids that are cleaner with low dielectric constant and with turbulence on the product’s surface. This type of guided wave radar device is also recommended for installations where the probe is near the tank wall or other obstacles.
Make sure that the device can withstand the range of temperature within the tank. Most GWR devices are rated up to 850 deg F or 450 deg C. You should select a device with added signal strength since this will result in increased reliability and accuracy of the devices.
Guided wave radar level transmitter with dynamic vapor compensation is recommended where a high level of accuracy is required under a high-pressure environment. The measurement taken from the device can compensate for changes in vapor dielectric, which results in improved accuracy.
Other factors that should be considered include mounting and proximity. Single probe configuration can be installed almost anywhere. But the single probe configuration can only to apply to specific situations.
Lastly, the probe length of the device should be of the right length. The length should be according to the measurement rate. This is an important consideration as it can help in ensuring accurate reading with minimum chances of an error.
Guided wave radar level transmitters can also be used with an agitator. However, certain things must be considered prior to use the device. The probe must be prevented from contacting the agitator blades. Make sure that you confirm the ability of the probe to withstand the force inside the medium. This is important since turbulent on the surface may decrease the accuracy of the measurement. You can install the device in a bypass chamber or stilling well for an agitated tank.