Do you know that many materials can hold electrical charges but are non-conducting? This type of material is called dielectric material. Usually, dielectric materials are non-metallic substances that have high specific resistance and high insulating resistance. This article will cover the properties, applications, and measurement techniques of dielectric materials.
Dielectric Properties
Electric charges will not flow through dielectric materials when placed between an electric field. Dielectric polarisation happens when the electric chargers are shifted a little from their equilibrium position.
The dielectric properties represent the obstruction produced by the dielectric materials in the formation of electric field. It is also known as relative permittivity which is expressed as a ratio of electric permittivity of the substance to the vacuum.
In general, relative permittivity is referred to as a dielectric constant. However, relative permittivity, is actually a combination of the constant, (real part) and loss factor, (imaginary part). Besides, loss tangent, is another common parameter that measures signal loss due to the inherent dissipation of electromagnetic energy.
Applications of Dielectric Properties Measurement
Understanding the dielectric properties of a material is very important. There is a wide range of applications for dielectric measurement. Dielectric measurement is very useful in the electronics industry especially when using it to characterize the substance used to design antennas, capacitors, substrates for PCB, etc. Other than the characterization of non-organic material, with different types of post-processing calculation, dielectric measurement can also helps in measuring fruit ripeness, human tissue characterization, and oil content analysis. Its usefulness goes beyond the electronic industry.
Measurement Techniques
Due to the wide range of applications and substances that can be measured, there are some challenges in dielectric measurement. In the measurement process, we need to identify the form of material under test (MUT) such as solid, semi-solid, liquid, and gas. Second, the thickness of solid material and volume of liquid also affects the measurement results’ accuracy. On the other hand, some measurement techniques are only able to measure a single frequency point instead of broadband measurement.
Due to these challenges, many research is done to study and design various measurement tools to fit different applications. The types of techniques include ring resonators, parallel-plate, waveguides, coaxial probes, free spaces, etc. Although each of the tools served different purposes in dielectric measurement, these fixtures are required to operate with a vector network analyzer (VNA) and a software application to control the VNA.
Here are two popular techniques that are being commonly used in research and industry.
Coaxial Probe
The first technique is the coaxial probe which is suitable for broadband usage. It is easy to use and non-destructive to the MUT. Hence, it can perform large-scale measurements in a short period of time. Solid, liquid, and semi-solid (powder) are all suitable for using this technique. The drawback of this technique is that the accuracy of the loss factor is limited for low-loss materials such as teflon.
Waveguide Tool
Another popular technique is the waveguide tool. By using waveguides, the magnetic properties can be measured. The closed environment measurement of the waveguide provides a highly accurate and precise measurement compared to a coaxial probe.
However, the measured frequency range is limited by the size of the waveguide launcher. In other words, this technique requires a lot of waveguides to obtain a broadband measurement, especially in the lower frequency ranges (100MHz-3GHz). Furthermore, the substances require pre-processing to ensure the thickness and size are able to fit in between 2 waveguide launchers.
Conclusion
In order to perform the measurement, identifying the types of elements to be measured and the requirements such as frequency range, measurement accuracy, material form, temperature, contacting or non-contacting, etc are pivotal. Even though dielectric measurement still requires post-processing to turn relative permittivity into a wider application, having accurate and precise measurement techniques are still very important.
FILPAL has developed a software that is able to obtain and do post-processing for dielectric properties measurement. We continue are continuously researching and improving on how to utilize software in conjunction with dielectric properties measurement techniques. Contact us at sales@filpal.com for more information of this software
Originally published at http://filpal.wordpress.com on November 27, 2022.
