Eddy Current Technology
Eddy current (ECT) technology is a noncontact method for the inspection of metallic parts. In this technique, the probe, which is excited with an alternating current, induces eddy current in the part under inspection. Any discontinuities or material property variations that change the eddy current flow in the part are detected by the probe as a potential defect.
Over the years, probe technology and data processing have continuously progressed so that the eddy current technique is now recognized to be fast, simple, and accurate. This is why the technique is widely used in the aerospace, automotive, petrochemical, and power generation industries for the detection of surface or near-surface defects in material such as aluminum, stainless steel, copper, titanium, brass, Inconel® and even carbon steel (surface defect only).

Benefits of Eddy Current
Eddy current offers the following capabilities:

Quick, simple, and reliable inspection technique to detect surface and near-surface defects on conductive material
Can be used to measure material electrical conductivity.
Measurement of nonconductive coating
Hole inspection with the use of high-speed rotating scanner and surface probe

Eddy Current Probes
R/D Tech's standard eddy current probes are available in different configurations:

Bolt hole probes
Surface probes, in various shapes and configurations
Low-frequency Spot and Ring type probes
Sliding probes
Wheel probes
Speciality probes made for specific applications
Reference standards with EDM notches can be manufactured according to the application specifications.

Probes used to perform eddy current inspections are made with a copper wire wound to form a coil. The coil shape can vary to better suit specific applications.

a-Alternating current flowing through the coil at a chosen frequency generates a magnetic field around the coil.
b-When the coil is placed close to an electrically conductive material, eddy current is induced in the material.
c-If a flaw in the conductive material disturbs the eddy current circulation, the magnetic coupling with the probe is changed and a defect signal can be read by measuring the coil impedance variation.

Surface preparation is minimal. Unlike liquid penetrant or magnetic particle inspection, it is unnecessary to remove the paint from the surface to inspect the parts.

Learn more about our eddy current probes

Eddy Current Software

Impedance Plane and Strip Chart Display

User-selectable screen persistency
Two-frequency operation and automatic mixing capability
Reference signal overlay can be kept on the screen for easier signal interpretation.
Freeze mode allows signal rotation and gain adjustment without having to hold the probe on the part.
Zoom and Best Fit functions

Conductivity and Thickness Measurement Mode

Simple step-by-step calibration procedure

Conductivity and thickness measurement

Material conductivity or coating thickness are displayed with very large numerals.
Impedance plane display for signal representation during measurement
Instruction window guides the operator during the measurement process.
Adjustable threshold represents the measurement values in blue, green, or red.
Measurements can be stored in a tabular report.

C-Scan Surface Mapping

Support of two encoder inputs to connect various scanners
Real-time C-scan mapping display with impedance plane and strip chart view

Advanced Real-Time Data Processing

Three alarms can be defined with various shapes to activate LED, buzzer, or TTL output.
High-pass, low-pass, and specialized filters

Eddy Current Modules Specifications*

Overall dimensions	244 mm x 182 mm x 57 mm (9.6 in. x 7.1 in. x 2.1 in.)
Weight	1.2 kg (2.6 lb)
Connectors	1 19-pin Fischer® eddy current probe connector 1 BNC connector
Number of channels	4 channels
Probe recognition	Automatic probe recognition and setup
Generator
Number of generators	1 (with internal electronic reference)
Maximum voltage	12 V p-p into 10 Ω
Operating frequency	20 Hz - 6 MHz
Bandwidth	8 Hz - 5 kHz (in single coil). Inversely proportional to the time slot duration and set by the instrument in multiplexed mode.
Receiver
Number of receivers	1 to 4
Maximum input signal	1 V p-p
Gain	28-68 dB
Internal multiplexer
Maximum voltage	12 V p-p into 50 Ω
Number of receivers	4 differential receivers (8 time slots each)
Maximum input signal	1 V p-p
Data acquisition
Digitizing frequency	40 MHz
Acquisition rate	1 Hz - 15 kHz (in single coil). The rate can be limited by the instrument's processing capabilities or by delays set by the multiplexed excitation mode.
A/D resolution	16 bits
Data processing
Phase rotation	0° to 360° with increments of 0.1°
Filtering	FIR low-pass, FIR high-pass, FIR band-pass, FIR band-stop (adjustable cutoff frequency), median filter (variable from 2 to 200 points), mean filter (variable from 2 to 200 points) a selection of IIR filers are also available
Channel processing	Mixing Interpolation
Data storage
Maximum file size	Limited by memory size
Data synchronization
On internal clock	1 Hz - 15 kHz (single coil)
External pace	Yes
On encoder	On 1 or 2 axes
Alarms
Number of alarms	3
Alarm zone shape	Pie, inverted pie, box, inverted box, and ring
Output type	Visual, audio, and TTL signals
Analog outputs	1 (X or Y)

Supporting Data

Questions?

Contact an Olympus NDT Specialist