Eddy Current Conductivity Measurement

Eddy Current Weld Inspection

One of the uses of eddy current instruments is for the measurement of electrical conductivity. The value of the electrical conductivity of a metal depends on several factors, such as its chemical composition and the stress state of its crystalline structure. Therefore, electrical conductivity information can be used for sorting metals, checking for proper heat treatment, and inspecting for heat damage.

The technique usually involves nulling an absolute probe in air and placing the probe in contact with the sample surface. For nonmagnetic materials, the change in impedance of the coil can be correlated directly to the conductivity of the material. The technique can be used to easily sort magnetic materials from nonmagnetic materials but it is difficult to separate the conductivity effects from the magnetic permeability effects, so conductivity measurements are limited to nonmagnetic materials. It is important to control factors that can affect the results such as the inspection temperature and the part geometry. Conductivity changes with temperature so measurements should be made at a constant temperature and adjustments made for temperature variations when necessary. The thickness of the specimen should generally be greater than three standard depths of penetration. This is so the eddy currents at the back surface of the sample are sufficiently weaker than the variations in the specimen thickness that are not seen in the measurements.

Conductivity Measurement will be useful for Aerospace, Automobile industries, Metals Processing units, Castings, Maintenance and Quality Assurance teams, Heat Treatment Specialists and those determining the purity of materials such as gold bullion and coins.

We have specifically developed probes to check for conductivity in materials.

Eddy Current Inspection finds in way into conductivity measurements for

• Aerospace
• Metals Processing
• Casting
• Heat Treatment Plants

 

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