Dielectric Constant and Dissipation Factor - ASTM D150
Dielectric Constant (Relative Permittivity)
The ratio of capacitance of a capacitor with test material as the dielectric to the capacitance of a capacitor with a vacuum as the dielectric. For materials that are to be used to insulate
electrical components the dielectric constant should be low. For materials that are to be used as a dielectric in a capacitor, the dielectric constant should be high so that the capacitor
dimensions can be minimized. The dielectric constant can be calculated using:
ε = Cs / Cv
where Cs is the capacitance with the specimen as the dielectric,
and Cv is the capacitance with a vacuum as the dielectric.
The ratio of the power dissipated in the test material to the power applied. Equal to the tangent of the loss angle, or the cotangent of the phase angle. The dissipation factor can be calculated
D = tan δ = cot θ = 1 / (2π f RpCp)
where δ is the loss angle,
θ is the phase angle,
f is the frequency,
Rp is the equivalent parallel resistance,
and Cp is the equivalent parallel capacitance.