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Salinity and sugar sensing using microstrip technology


By Md. Naimur Rahman and Mohammad Tariqul Islam, Universiti Kebangsaan, Malaysia, and Md. Samsuzzaman, Patuakhali Science and Technology University, Bangladesh

Conditions like diabetes, stroke, kidney failure among others are on the increase, partly because of modern-day high intake of salt and sugar.

To monitor these in the food and beverage industry, as well as medicine and even agriculture, there are various ways to measure salt and sugar content. The open-ended coaxial probe is one of them, which measures the dielectric properties of food and liquids; however, this process is time-consuming and complex, and system development is costly.

Another measurement method, based on microstrip technology, is considered simple and cost-effective. Dielectric-based sensors read the dielectric and physical properties of a material; they can also sense moisture, temperature, bulk density, and other parameters.

Microstrip Patch Antenna as a Sensor

A fringing field that originates from an antenna patch and affects the substrate causes electromagnetic radiation, affecting the permittivity of the substrate and hence the performance of the patch sensor.

A coaxial or probe feed is directly attached to the patch to reduce this radiation, allowing the antenna to operate in a large bandwidth. The performance of a microstrip patch antenna depends on several factors, including its size and shape, with the size changing the resonance frequency of the antenna.

In this project, the sensor measures the reflection coefficient of the sensing antenna within different concentrated salt and sugar solutions.

The dielectric properties change due to the bond between dissolved ions and water molecules when salt or sugar are added to the water. This change reduces the polarisation of water and decreases the dielectric constant.

The effective dielectric constant also decreases, given the reduction in dielectric constant. Hence, the load impedance increases and, consequently, the reflection coefficient decreases.

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