Coil (Probe) Design
The most important feature in eddy current testing is the way in which the eddy currents are induced and detected in the material under test. This depends on the design…
Probes – Shielding & Loading
One of the challenges of performing an eddy current inspection is getting sufficient eddy current field strength in the region of interest within the material. Another challenge is keeping the…
Probes – Configurations
Eddy current probes are classified by the configuration and mode of operation of the test coils. The configuration of the probe generally refers to the way the coil or coils…
Absolute Probes
Absolute probes generally have a single test coil that is used to generate the eddy currents and sense changes in the eddy current field. As discussed in the physics section,…
Display – Analog Meter
Analog instruments are the simplest of the instruments available for eddy current inspections. They are used for crack detection, corrosion inspection, or conductivity testing. These types of instruments contain a…
Display – Complex Impedance Plane
Electrical Impedance (Z), is the total opposition that a circuit presents to an alternating current. Impedance, measured in ohms, may include resistance (R), inductive reactance (XL), andcapacitive reactance (XC). Eddy current circuits usually have only R and…
Bridges
The bridge circuit shown above is known as the Maxwell-Wien bridge (often called the Maxwell bridge), and is used to measure unknown inductances in terms of calibrated resistance and capacitance.…
Resonant Circuits
Eddy current probes typically have a frequency or a range of frequencies that they are designed to operated. When the probe is operated outside of this range, problems with the data…
Eddy Current Instruments
Eddy current instruments can be purchased in a large variety of configurations. Both analog and digital instruments are available. Instruments are commonly classified by the type of display used to present the…
