Apparatus for determining properties of an electrically conductive object
AssigneeRontgen Technische Dienst B.V.
InventorV. O. de Haan
Life of this patent
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Abstract
Eddy currents are generated in an object constructed of a conductive material by transmitting an electromagnetic signal to the object and detecting electromagnetic signals generated by eddy currents induced in the object, and an electromagnetic signal V(t) is described by a product of two factors F and G(t), wherein F is a function of the geometry and electrical and magnetic properties of the material and G(t) is a function of geometry of the material, the electrical and magnetic properties of the material, the thickness perpendicular to the surface of the material, and time.
Claims14
A method for determining properties of an electrically conductive object to be measured, comprising the steps of:
- transmitting a time varying electromagnetic field from a transmit antenna to said object for generating eddy currents in said object;
- detecting an electromagnetic signal S(t) generated by said eddy currents using a receiving antenna;
- and
- determining properties of said object from said signal S(t) by selecting certain τi and σ i μ i
- such that S ( t ) = ∑ i = 1 n θ i F i G i ( t ) with ( 1 ) F i = δ σ i μ i ( 2 ) G i ( t ) = t γ 1 + α ( β t τ i ) m ⅇ β t τ i ( 3 )
- i=1, 2, . . . n (4)
- and ∑ i = 1 n θ i = 1 ( 5 )
- wherein α, β, γ, δ, and m are real numbers dependent on geometry of said object, of said transmitting antenna and of said receiving antenna;
- wherein said real numbers are further dependent on relative positions of said object, said transmitting antenna and said receiving antenna;
- wherein μi represents magnetic permeability of an area i of said object and σi represents electrical conductivity of an area i of said object;
- and
- wherein said areas i (i=1, 2, . . . n) together generate said electromagnetic S(t).
Apparatus for determining properties of an object to be measured, said apparatus comprising:
- a transmitter unit;
- a transmit antenna coupled to said transmitter unit;
- a receiver unit;
- a receiver antenna coupled to said receiver unit;
- and
- a computer coupled to said transmitter unit and said receiver unit;
- said computer operative to control said transmitter to transmit a time varying electromagnetic field to said object for generating eddy current in said object;
- said receiver unit operative to detect an electromagnetic signal S(t) for determining parameters τi and σ i μ i
- such that:
- S ( t ) = ∑ i = 1 n θ i F i G i ( t ) with ( 1 ) F i = δ σ i μ i ( 2 ) G i ( t ) = t γ 1 + α ( β t τ i ) m ⅇ β t τ i ( 3 )
- i=1, 2, . . . n (4)
- and ∑ i = 1 n θ i = 1 ( 5 )
- wherein α, β, γ, δ are real number representing characteristics of geometry of said object, said transmitting antenna and said receiving antenna and of relative positions of said object, said transmitting antenna and said receiving antenna and wherein μi represents magnetic permeability of an area i of said object and σi represents electrical conductivity of said area i of said object;
- and
- wherein said areas i(i=1,2), . . . n) together generate said electromagnetic signal S(t).
Dependencies are inferred from the claim text.