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EC Formula
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Home - General Resources - Eddy Current Inspection Formula - Ohm's Law Impedance Phase Angle Magnetic Permeability Where: I Current (amp) V Voltage (volt) Z Impedance (ohm) More Information Ohm's Law Calculator Where: Z Impedance (ohm) R Resistance (ohm) X L Inductance Reactance(ohm) More Information Where: Phase Angle (deg) X L Inductance Reactance(ohm) R Resistance (ohm) More Information Phase Angle Calculator Where: Magnetic Permeability (Henries/meter) B Magnetic Flux Density (Tesla) H Magnetizing Force (Am/meter) Relative Magnetic Permeability Conductivity & Resistivity Electrical Conductivity (%IACS) Electrical Conductivity (%IACS) Where: r Relative Magnetic Permeability (dimensionless) Any Given Magnetic Permeability (H/m) o Magnetic Permeability in Free Space (H/m), which is 1.257 x 10 -6 H/m More Information Where: Electrical Conductivity Siemens/m Electrical Resistivity (ohm-m) More Information When resistivity is known Where: IACS Electrical Conductivity (% IACS) Electrical Resistivity ( ohm-cm) S/cm Electrical Conductivity ( Siemens/cm) More Information When conductivity in S/m or S/cm is known or Where: IACS Electrical Conductivity (% IACS) S/m Electrical Conductivity (Siemens/meter) S/cm Electrical Conductivity ( Siemens/cm) More Information Current Density Standard Depth of Penetration Standard Depth of Penetration Standard Depth of Penetration Where: J x Current Density (amps/m 2 ) J o Current Density at Surface (amps/m 2) e Base Natural Log = 2.71828 x Distance Below Surface Standard Depth of Penetration More Information When electrical conductivity (S/m) is known. Where: Standard Depth of Penetration (m) 3.14 f Test Frequency (Hz) Magnetic Permeability (H/m) (1.257 x 10 -6 H/m for nonmagnetic mat'ls) Electrical Conductivity (Siemens/m) More Information Depth of Pen Calculator When electrical conductivity ( IACS) is known. In mm In inches Where: Standard Depth of Penetration (mm or in) f Test Frequency (Hz) r Relative Magnetic Permeability (dimensionless) Electrical Conductivity (%IACS) More Information When electrical resistivity ( ohm-cm) is known. In mm In inches Where: Standard Depth of Penetration (mm or in) Electrical Resistivity ( ohm-cm) f Test Frequency (Hz) r Relative Magnetic Permeability (dimensionless) More Information
description
EC Formula
Transcript of EC Formula
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Home - General Resources-
Eddy Current Inspection Formula-
Ohm's Law Impedance Phase Angle MagneticPermeability
Where:
I Current (amp)V Voltage (volt)
Z Impedance (ohm)
More InformationOhm's Law Calculator
Where:
Z Impedance (ohm)R Resistance (ohm)XL Inductance
Reactance(ohm)
More Information
Where:
Phase Angle (deg)
XLInductanceReactance(ohm)
R Resistance (ohm)
More InformationPhase Angle Calculator
Where:
Magnetic Permeability(Henries/meter)
B Magnetic Flux Density(Tesla)H Magnetizing Force
(Am/meter)
Relative Magnetic
PermeabilityConductivity &
ResistivityElectrical
Conductivity(%IACS)
Electrical Conductivity
(%IACS)
Where:
rRelative MagneticPermeability(dimensionless)
Any Given MagneticPermeability (H/m)
o
MagneticPermeability in FreeSpace (H/m), which is1.257 x 10-6 H/m
More Information
Where:
ElectricalConductivitySiemens/m
ElectricalResistivity(ohm-m)
More Information
When resistivity is known
Where:
IACSElectricalConductivity(% IACS)
ElectricalResistivity(ohm-cm)
S/cmElectricalConductivity(Siemens/cm)
More Information
When conductivity in S/m or S/cm is known
or
Where:
IACSElectricalConductivity(% IACS)
S/mElectricalConductivity(Siemens/meter)
S/cmElectricalConductivity(Siemens/cm)
More Information
Current Density Standard Depthof PenetrationStandard Depthof Penetration
Standard Depthof Penetration
Where:
JxCurrent Density(amps/m2)
Jo Current Density atSurface (amps/m2)
e Base Natural Log =2.71828x Distance Below Surface Standard Depth of
Penetration
More Information
When electrical conductivity(S/m) is known.
Where:
Standard Depth ofPenetration (m)
3.14f Test Frequency (Hz)
MagneticPermeability (H/m)(1.257 x 10-6 H/m fornonmagnetic mat'ls)
ElectricalConductivity(Siemens/m)
More Information Depth of Pen Calculator
When electrical conductivity ( IACS) is known.
In mm
Ininches
Where:
Standard Depth ofPenetration (mm or in)
f Test Frequency (Hz)
rRelative MagneticPermeability(dimensionless)
ElectricalConductivity(%IACS)
More Information
When electrical resistivity (ohm-cm) is known.
In mm
Ininches
Where:
Standard Depth ofPenetration (mm or in)
Electrical Resistivity(ohm-cm)
f Test Frequency (Hz)
rRelative MagneticPermeability(dimensionless)
More Information
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Standard Depth of PenetrationVersus Frequency Chart
Eddy Current Field Phase Lag
Eddy Current Field Phase Lag
Eddy Current Field Phase Lag
Eddy Current Field Phase Lag
InRadians
InDegrees
Where:
Phase Lag (Rad orDegrees)
x Distance Below Surface(in or mm) Standard Depth of
Penetration (in or mm)
More Information
When electrical conductivity(S/m) is known.
Where:
Phase Lag (degrees)
x Distance BelowSurface (m) 3.14f Test Frequency (Hz)
rRelative MagneticPermeability
Electrical Conductivity(Siemens/m)
More Information
When electrical conductivity ( IACS) is known.
In mm
Ininches
Where:
Phase Lag (degrees)
x Distance BelowSurface (mm)f Test Frequency (Hz)
rRelative MagneticPermeability(dimensionless)
ElectricalConductivity(%IACS)
More Information
When electrical resistivity (ohm-cm) is known.
In mm
Ininches
Where:
Phase Lag (degrees)
x Distance BelowSurface (inch)
Electrical Resistivity(ohm-cm)
f Test Frequency (Hz)
rRelative MagneticPermeability(dimensionless)
More Information
Standard Depth ofPenetration and
Phase Angle
Material ThicknessRequirement for
Resistivity orConductivity
Measurement
FrequencySelection
for ThicknessMeasurement of
Thin Materials
Frequency Selectionfor Flaw Detection and Nonconductive Coating ThicknessMeasurements
Std.Depth
RelativeStrengthof EC
Phase Lag
0 e0=100% 0 rad = 0o
d e-1=37% 1 rad = 57.3o
2d e-2=14% 2 rad = 114.6 o
3d e-3=5% 3 rad = 171.9 o
4d e-4=2% 4 rad = 229.2 o
5d e-5=0.7% 5 rad = 286.5 o
When measuring resistivity orconductivity, the thickness ofthe material should be at least 3times the depth of penetrationto minimize material thicknesseffects
Where:
t Material Thickness
Standard Depth ofPenetration
More Information
Selecting a frequency thatproduces a standard depth ofpenetration that exceeds thematerial thickness by 25% willproduce a phase angle ofapproximately 90obetween theliftoff signal and the materialthickness change signal.
More Information
Defect Detection A test frequency that puts thestandard depth of penetration atabout the expected depth of thedefect will provide good phaseseparation between the defectand liftoff signals.
Nonconductive CoatingThickness MeasurementTo minimize effects from thebase metal the highestpractical frequency should beused.
