The following entries are defined in terms of material measurements with the N1500A software.
to take in electromagnetic energy, usually as heat.
distinct frequency bands at which electromagnetic energy is strongly coupled into a material and absorbed.
dielectric loss (as D for capacitors, but excluding DC “leakage”).
data format, with ε " on vertical axis and ε ’ on horizontal axis, with frequency as the independent parameter not displayed; lossy materials with relaxation mechanisms follow a semi-circle on these plots.
usually ionic dielectric loss; in dielectric measurements, does not mean true conduction (movement of electrons).
dissipation factor; usually measured for capacitors; D = tan δ .
Simplified model to explain dielectric properties versus frequency, assuming that a simple rotational relaxation phenomenon is acting.
angle Delta formed between the x-axis and the permittivity vector; δ is small (nearly 0 °rees; for low-loss materials, and large (up to about 45 ° ) for lossy materials; see tan δ (used more often)
polarization in a material lags behind the applied field in time; modeled by relaxation process; related to losses
Κ ratio of electric field storage capacity in a material to that of free space; usually means real (lossless) case only.
energy lost (absorbed) in material when applying an AC electric field; may be due to ionic, polar, atomic, or electronic mechanisms
dielectric mechanism; see “rotational”
a structure where the net charge distribution can be represented by the two equal and opposite charges separated by distance
propagation characteristics change with frequency
D; ratio of energy lost to energy stored (per cycle) in a system; same as tan δ , inverse of Q.
Dielectric mechanism (resonant, very weak, at very high frequencies), where the “orbits” of electrons around a nucleus are stretched”
Epsilon, symbol for absolute permittivity; sometimes also refers to permittivity relative to free space when the subscript r is dropped.
symbol for permittivity relative to free space, also called relative permittivity. It is a complex number, ε r* = ε r' - j ε r".
water molecules which are not “bound” and are free to orient themselves in an electric field
having uniform properties throughout; non-homogeneous materials are usually mixtures of two or more materials.
temporary dipoles, created by electric fields
a dielectric mechanism (fairly strong, lossy, operating at all frequencies), where mobile ionic charges migrate in a material
properties do not vary with orientation; non-isotropic materials are usually fibrous or crystalline
Kappa, another symbol for permittivity, always relative to free space. If complex, Κ r * = Κ r ' - j Κ r ". Sometimes refers just to the real part of permittivity.
see δ
The imaginary part of permittivity ε r" or Κ r " .
The imaginary part of permittivity ε r" or Κ r "
another term for tan δ and Dissipation Factor
Material Under Test
Non-Destructive Evaluation
attribute of test method, when material can be used for its end-purpose after testing.
distance through a lossy dielectric over which the field strength falls by 1/e due to energy absorption
molecular structures that inherently have a non-symmetrical charge distribution
measure of effect a material has on magnetic fields; ratio of flux over field.
measure of effect a material has on electric fields; ratio of flux over field
see θ
see δ
having permanent electric dipoles
to align dipoles in electric field
sin δ (or cos θ)
quality factor
ratio of energy stored over the energy lost (per cycle) in a system, inverse of tan δ and D
permittivity relative to free space. see ε r
see τ
see τ
free-space wavelength corresponding to the frequency 1/ τ
dipoles (such as H2O molecules) which are bound to a host material, and so are restricted in their ability to become oriented in an electric field
a dielectric mechanism (relaxation, fairly strong, often lossy, at moderate frequencies), where permanent dipoles (often entire molecules) “rotate” to align with an electric field
material that can respond to electromagnetic fields
ratio of ε r" over ε r'. Indicates relative lossiness of material
relaxation time constant; for a simple substance, the time it takes for 1/e of the constituent molecules to become aligned in response to an electric field
angle between real-axis and vector representing sum of storage and loss vectors