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fadzleyna
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what is the formula to calculate planar interdigitated electrodes for dielectric sensor ?
Baluncore said:To measure the water contamination of cooking oil you can measure the dielectric constant of the emulsion through the wall of a plastic or glass container. There are several design choices that can make that possible. It might also be possible to measure the dielectric loss angle of the emulsion, but I think the water content will be quite detectable by capacitance alone since the oil and water have very different dielectric constants.
A problem you may have is that wet oil may settle to the bottom of the container and your sensor may be measuring the characteristics of the clear oil that rises above the wet oil. It is also possible that water will react with the oil to make a hydrocarbon hydroxide. That sludge may have a similar dielectric constant to the good oil. It might be better to use density rather than dielectric constant in that case.
Planar interdigitated electrodes are good for sensing material that is very close to the electrodes. The electric field geometry between the electrodes will be of a similar form, independent of the scale.
Since the sensor must “look” through the wall of the container, it should use a large sensor with wide separation between electrodes and a deep field. That will sample a greater volume of the oil. A very small sensor with many fingers will measure the characteristics of the container wall material only, with very little influence from the oil. The less sensor fingers you use, the bigger can be the sensor gaps and the deeper the sensor field can sample into the oil. There may be a small irregular gap between the wall and the sensor. The effect of that gap will be less for a large sensor than for a small sensor. You might consider a grease between the sensor and the bottle to eliminate the airgap.
Another problem is screening the sensor from behind. If a metallic screen is used and if that is placed close to the back of the sensor, then it will increase the fixed capacitance and so reduce the influence of the fluid. I would consider placing a slab of “closed cell foam” behind the sensor. Outside that foam I would attach a sheet metal screen for the sensor assembly. The thickness of a low dielectric constant foam will reduce the fixed capacitance. The screen will keep out external electrical interference. The sensor electronics can also be placed inside that foam cavity.
It might be good to use two differential electrodes inside a grounded case. The advantage of that configuration would be better screening and isolation from the external environment.
So I am suggesting you use a large differential pair of electrodes rather than a planar interdigitated electrode array.
Revoke your decision, or compromise by building a “two finger” interdigitated electrode array.fadzleyna said:but i had decide to use interdigitated electrodes in my proposal. what should i do now?
Planar interdigitated electrodes are a type of electrode configuration used in electrochemical sensors and biosensors. They consist of two sets of parallel, interlocking electrodes on a flat surface, with alternating positive and negative terminals.
The purpose of planar interdigitated electrodes is to facilitate the measurement of small changes in electrical current or potential at the electrode surface. This can be used to detect the presence of certain substances or biomolecules in a sample, making them useful for sensing applications.
Planar interdigitated electrodes are typically fabricated using techniques such as photolithography or screen printing on a substrate material, such as glass or silicon. The electrodes are then coated with a conductive material, such as gold or carbon, to improve their sensitivity and stability.
Some advantages of planar interdigitated electrodes include their small size, low cost, and high sensitivity. They also allow for rapid and easy analysis of samples, making them ideal for use in portable or point-of-care devices. Additionally, their planar design allows for easy integration with other electronic components.
Planar interdigitated electrodes have a wide range of applications, including environmental monitoring, medical diagnostics, food safety testing, and chemical analysis. They are also commonly used in the development of lab-on-a-chip devices for point-of-care testing and in research for studying electrochemical reactions and kinetics.