The applications of Time Domain Reflectometry (TDR) probes in engineering and the natural sciences has been of interest since the 1930s, where it was a recognised technique to test electrical connections in cables. This probe detects signals that travel through a material and then reflected back, where the reflections depend on the interaction between the electromagnetic field and the material under test.

Nowadays, this technique has been extended to many applications in geophysics, agriculture and medi­cal fields. Studies on developing an innovative kind of probe could broaden fields of applications such as biomedical analyses, for example the way that human blood reacts to electrical properties or other liquid organic substances.

The evolution of testing of electrical properties moved towards electrical insulators, known as dielectrics, which have the ability to be polarised in an electric field. These dielectrics are commonly used in capacitors as well as for the manufacturing of electrical and electronics systems and equipment, with the ability to store electrical energy. The presence of dielectric materials in an electrical field produces electrical polarisation, because the electrons rotate to align with the applied field. This creates a charge separation and this slight separation reduces the electric field within the dielectric.

The polarisation ability of a material is defined as the permittivity of the material, which measures the ease or difficulty to form an electrical field inside the material of the dielectric. Likewise, permeability is a measure of the abi­lity to form a magnetic field inside a magnetic material.

Measurements of permittivity and permeability is essential not only to define moisture in the soil, but also to provide users with site measurement options for monitoring of landslides. It can be used to detect water condensation pro­cesses in buildings during wintertime, and can serve as a good assessment tool for design solutions for civil engineers.

Furthermore, applications of electrical properties in agriculture and food processing industries have been of interest for many years. Knowledge of dielectric properties of foods as a function of moisture content gauges the quality of milk powder that is essential for consumption. The permittivity of biological tissues is also very important in applied problems of electrical simulation, in studying human electromagnetic field interactions and development of diagnostic and therapeutic medical applications.

The knowledge of dielectric permittivity and magnetic permeability for a wide class of materials can be achieved using the TDR technique, which is based on the velo­city of the electromagnetic waves in the investigated medium, such as soil and human tissues.

Other applications of the TDR probes are for quality monitoring, such as in corns or olive oil. It can also be used in the identification of polluting substances, such as hydrocarbons or waste products of some industries, such as those producing leather and varnishes.

With so many applications, the Physics Department at the University of Malta, funded by the Take-Off Seed Fund Award, is on a quest to further analyse and develop these probes.

Dr Iman Farhat works at the Department of Physics at the Faculty of Science and Institute of Space Sciences and Astronomy.

Did you know?

• Herbert Johnson was an engineer who invented the electrical standing mixer in 1908.

• The Great Man-Made River is a network of pipes that supplies water to the Sahara in Libya, from the Nubian Sandstone Aquifer System fossil aquifer.

• When helium is cooled to almost absolute zero (-273ºC), it becomes a liquid with surprising properties: it flows against gravity and it will start running up and over the lip of a glass container.

• A massive crack suddenly appeared in Kenya, prompting new discussions on the breakup of Africa into two landmasses. The process, however, will take millions of years.

• Kiwis are flightless birds, native to New Zealand.

For more trivia, see: www.um.edu.mt/think

Sound bites

• Earth’s atmosphere consists of a mixture of gases, primarily nitrogen and oxygen. However, moving upwards into space, the structure of the air envelop changes. At about 80 km above the Earth’s surface, the atmosphere is made up of ionised gas, which consists of a balanced mix of electrons, positive ions and neutral particles. This state is called plasma, commonly known as the fourth state of matter. In fact, according to many astrophysicists, it is the very first state since it was the first to form immediately after the Bing Bang.

https://www.sciencelearn.org.nz/resources/238-plasmas-explained

• Optical telescopes, such as the fa­mous Hubble Space Telescope, detect the intensity of incoming radiation in the optical band of the spectrum. Fundamentally, all celestial objects emit electromagnetic radiation, among them radio waves. The observation of cosmic objects in these radio frequencies is defined as radio astronomy. Since radio waves are able to penetrate dust, scientists utilise radio astronomy techniques to explore undetectable areas of space that cannot be seen using visible light by optical telescopes. Unlike optical telescopes, the wavelength of radio emissions is longer. Hence, the radio telescopes must have a much larger collecting area to obtain the same level of detail and resolution as their optical cousins. The largest radio telescope in the world as a single dish is the Arecibo telescope, which featured in the movie Contact, and is located in a natural hollow in Puerto Rico, South America.

https://www.skatelescope.org/radio-astronomy/

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