how to calculate conductivity of material from permittivity.

[veerubiji]

Hi,

I am able to measure relative permittivity of fluied(εr), I want to calculate conductivity of same fluid. Can anyone suggest me how to do it?

I found one formula to calculate conductivity from this forum itself but i am not sure it is right or wrong. The formula as shown below.

ε = εrεo + j * σ/ω.

but i know that

ε = εrεo

if this is equal then what will be the (σ) should be zero according to this formula.

I am thinking the above one is wrong.....

can anyone tel me how to calculate conductivity from permittivity ?

 

[godfreyl]

You can't calculate conductivity from permittivity. They are independent.

 

[ArNvC]

In Phasor mode the dielectric constant is considered to be a complex number consisting:
ε = εrεo + j * σ/ω
where:
εr = relative permittivity
εo = permittivity of free space
σ = electrical conductivity
ω = angular frequency = 2πf

Also, j * σ/ω is the dielectric loss factor, ie complex permittivity in linear media and how it is related to the dielectric constant and the conductivity. In the restricted case of linear media, there are the Kramers-Kronig relations which expresses conductivity as an integral of dielectric constant over all frequencies, and also expresses dielectric constant as an integral of conductivity over all frequencies.

See: https://scienceworld.wolfram.com/physics/Kronig-KramersRelations.html

 

[WimRFP]

You can specify a conductivity based on:

J = E*(σ + j*ε0*εr*ω), where J in A/m^2, E in V/m.
Re(J) is the "resistive" current density and Im(J) is the "capacitive" current density, when the E phasor has a real component only.

So the complex conductivity for a material is J/E = σ + j*ε0*εr*ω

You may know that both σ and εr are frequency dependent for many materials.

Are you really measuring j*ε0*εr*ω, or |σ + j*ε0*εr*ω|?

 

[phongphanp]

I think we can only calculate formular for plate (and else by datasheet) but testing must be on STD room .