Locator - Eddy Current Gaugestaffweb.itsligo.ie/staff/dsheridan/Eddy Current Lab.pdf · Declan Sheridan 1 Locator - Eddy Current Gauge Introduction: This is a general purpose Eddy

Declan SheridanDeclan Sheridan 11

Locator Locator -- Eddy Current GaugeEddy Current GaugeIntroduction: Introduction:

This is a general purpose Eddy Current Gauge for general This is a general purpose Eddy Current Gauge for general surface (metal, carbon fibre, conducting materials), can do surface (metal, carbon fibre, conducting materials), can do limited subsurface and conductivity tests. limited subsurface and conductivity tests.

� not reliant on contact (as Ultrasonic is) can be � not reliant on contact (as Ultrasonic is) can be used through paint.used through paint.

� no � no couplantcouplant required such as oil, gel.required such as oil, gel.� actually can be better if no contact� actually can be better if no contact

Greater the conductivity of the material, the greater the penetrGreater the conductivity of the material, the greater the penetrationationGreater the permeability of the material, the lesser the penetraGreater the permeability of the material, the lesser the penetrationtion

The magnetic field will pass straight through if the material The magnetic field will pass straight through if the material is non conductor.is non conductor.


Locator Locator -- Eddy Current GaugeEddy Current Gauge

�� ApplicationsApplications

�� Basic Surface inspectionBasic Surface inspection�� Sub surface defectsSub surface defects�� Material sortingMaterial sorting�� Used extensively in North Sea Oil field doing welding Used extensively in North Sea Oil field doing welding

checks.checks.�� “Dope on a Rope” is the non flattering term for the operator “Dope on a Rope” is the non flattering term for the operator

who is hung over the platform performing the checks.who is hung over the platform performing the checks.�� In service aircraft due to ability to pass through air, e.g. In service aircraft due to ability to pass through air, e.g.

laminated materials so you can “see” through layerslaminated materials so you can “see” through layers



��

��

Magnetic Field of a Coil :Magnetic Field of a Coil :--

+ ve+ ve

-- veve

DCDC

NorthNorth

SouthSouth



�� The field of the eddy current diminishes with depth.The field of the eddy current diminishes with depth.

�� The eddy currents produce a magnetic field that opposes The eddy currents produce a magnetic field that opposes the primary field.the primary field.

��

Production of Eddy Currents :Production of Eddy Currents :--

ACAC

Eddy CurrentsEddy Currents

AlternatingAlternating(moving)(moving)Primary Primary

Field Field

Conductive Material



�� The gauge measures the impedance of the coil which is The gauge measures the impedance of the coil which is altered by the opposing magnetic field.altered by the opposing magnetic field.

��

Ferrous Materials

Non Ferrous Materials

Air

Copper

Al Alloy

Titanium

Steel

Reactance

Resistance

µ

Cond.



�� Procedure for Surface Inspection.Procedure for Surface Inspection.

�� Cable Cable –– surface / sorting cable surface / sorting cable 39A001 or 29A00139A001 or 29A001�� Attach the pencil probe Attach the pencil probe 106P4106P4 -- N.B. N.B. ““AbsoluteAbsolute”” setting on the menusetting on the menu�� Use the surface defect reference block Use the surface defect reference block 29A02929A029�� Frequency set to 2 MHzFrequency set to 2 MHz�� Set probe on menu to Set probe on menu to ““AbsoluteAbsolute”” typetype�� Set the gain to 30dB.Set the gain to 30dB.�� Set the X:Y ratio to 1:4Set the X:Y ratio to 1:4�� Calibrate by holding the probe on the test block. Press Balance/Calibrate by holding the probe on the test block. Press Balance/Load. Load.

Long press on the Exec/Lift Off, to calibrate in air. Long press on the Exec/Lift Off, to calibrate in air. �� Set Set ““PersistancePersistance”” setting to permanent, so that the responses remain.setting to permanent, so that the responses remain.�� Each of the defects give a different size response, see the nextEach of the defects give a different size response, see the next slideslide





�� Material Sorting:Material Sorting:

�� High speed operation, due to electrical response, so High speed operation, due to electrical response, so good for production processes.good for production processes.

�� Highlights the Reactance Highlights the Reactance –– Resistance graph.Resistance graph.

�� Marked changes in phase when the probe goes from Marked changes in phase when the probe goes from one material to another with a different conductance.one material to another with a different conductance.


Locator Locator -- Eddy Current GaugeEddy Current Gauge�� Procedure for Material Sorting.Procedure for Material Sorting.�� Cable Cable –– surface / sorting cable surface / sorting cable 39A001 or 29A00139A001 or 29A001�� Probe 808P2 N.B. Probe 808P2 N.B. ““AbsoluteAbsolute”” setting on the menusetting on the menu�� Use Material sorting reference block Use Material sorting reference block 33A15133A151�� Frequency set to 500 kHzFrequency set to 500 kHz�� Set probe on menu to Set probe on menu to ““AbsoluteAbsolute”” typetype�� Set the gain to be very low, only interested in the phase angle.Set the gain to be very low, only interested in the phase angle.�� Set Set ““Input GainInput Gain”” to low.to low.�� Balance in air, press Balance/LoadBalance in air, press Balance/Load�� Set Set ““PersistancePersistance”” setting to permanent, so that the responses remain.setting to permanent, so that the responses remain.�� Desired is that Copper is along the +Desired is that Copper is along the +iveive XX--axisaxis�� Go to the phase setting and press Go to the phase setting and press and and arrows until it is roughly in arrows until it is roughly in

position.position.�� Reset the gain until the response just fills the screen.Reset the gain until the response just fills the screen.�� Each material gives a different phase angle.Each material gives a different phase angle.



�� Response:Response:



�� Remember the graph!!!Remember the graph!!!



�� Procedure for Sub surface inspection. Procedure for Sub surface inspection. �� Uses are for layered structures such as aeroplanes.Uses are for layered structures such as aeroplanes.�� Cable Cable –– reflection cable reflection cable 39A005 or 33A13039A005 or 33A130�� Reflection Probe 700P24AReflection Probe 700P24A�� Use rUse reference plates 33A048eference plates 33A048�� Frequency set to 3 kHzFrequency set to 3 kHz�� Set probe on menu to Set probe on menu to ““ReflectionReflection”” typetype�� Set the X:Y ratio to 1:1Set the X:Y ratio to 1:1�� Set Set ““Input GainInput Gain”” to high.to high.�� Balance is not required, but Lift off is. Press Exec/Left off keBalance is not required, but Lift off is. Press Exec/Left off key and when y and when

told to lift the probe.told to lift the probe.�� Set Set ““PersistancePersistance”” setting to permanent, so that the responses remain.setting to permanent, so that the responses remain.�� The gauge will give a different (phase) angle for a defect on a The gauge will give a different (phase) angle for a defect on a different different

layer.layer.

Documents

Locator - Eddy Current Gaugestaffweb.itsligo.ie/staff/dsheridan/Eddy Current Lab.pdf · Declan Sheridan 1 Locator - Eddy Current Gauge Introduction: This is a general purpose Eddy