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Epsilon Questions >  Answer 2

Epsilon Answer 2

What is dielectric permittivity and why is it relevant ?

Dielectric permittivity, also known as dielectric constant, is a property of insulating materials that characterises their interaction with an electric field. It is relevant because the Epsilon sensor responds to capacitance and capacitance depends on dielectric permittivity. The reason we emphasise dielectric permittivity rather than capacitance is calibration. Dielectric permittivity is a material property that can be used for calibration, whereas capacitance is a device property for which no calibration standards are available. The common symbol used for dielectric permittivity is the Greek letter Epsilon (ε) and this is where the Epsilon got its name from.

The dielectric permittivity of some common materials is listed in the table below.

Material ε
Air 1.0
Petroleum Jelly 2.1
Ethyl Acetate 6.0
Ethylene Dichloride 10.4
Isopropyl Alcohol 17.9
Ethanol 24.5
Methanol 30.0
Nitrobenzene 34.8
Ethylene Glycol 37.0
DMSO 46.7
Glycerol 47.0
Water 80.1

As can be seen in the table above, water has a particularly high dielectric permittivity and this is what capacitance-sensing instruments such as the Corneometer® and the Epsilon rely on for measuring hydration.

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