Application Cases

Experiment Name: Application of Power Amplifiers in Pulsed Eddy Current Testing for Defects in Double-Layer Heterogeneous Metal Casing

Experimental Equipment:
Signal generator, ATA-4014 high-voltage power amplifier, signal amplifier, filter, PC, detection probe, and test casing.

Experimental Content:
Focusing on pulsed eddy current testing technology, this study investigates the classification, identification, and quantitative evaluation of wall-thinning defects in a typical double-layer heterogeneous metal casing structure (inner tube: stainless steel; outer tube: carbon steel).

Experimental Procedure:

(1) Establishment of Simulation Model:
The detection probe consists of an excitation coil, a ferromagnetic core, and a magnetic field sensor.

(2) Excitation Current Signal Used in Simulation:
The excitation current signal, as shown in the figure, has a frequency of 33 Hz, a duty cycle of 33%, and a maximum current intensity of 1 A. It is used to drive the excitation coil (with 1350 turns) in the probe to generate a primary magnetic field.

2. Pulsed Eddy Current Testing Experimental Platform:
The constructed pulsed eddy current testing system mainly consists of a signal generator, power amplifier, signal amplifier, filter, PC, detection probe, and test casing. When a transient excitation current (such as a square wave) is applied to the excitation coil in the detection probe, a primary magnetic field (coil magnetic field) is generated. This magnetic field induces eddy currents in the metal test casing, which in turn produce a secondary magnetic field (eddy current-induced magnetic field) opposite in direction to the primary magnetic field and inhibiting its changes. The detection signal picked up by the magnetic field sensor in the probe is the combined magnetic field signal of the primary and secondary magnetic fields. Since defects in the metal casing cause changes in the eddy currents and the secondary magnetic field, thereby altering the intensity of the combined magnetic field, the detection signal contains defect information. By analyzing this signal, parameters such as the location and size of defects can be determined.

Experimental Results:
There is a clear boundary between the distribution regions of characteristic points corresponding to the two types of defects. Additionally, the characteristic points for each defect type show regular distribution patterns as the thinning amount changes, indicating that the proposed defect classification and identification method can effectively classify and identify wall-thinning defects in the inner and outer tubes of double-layer heterogeneous metal casings.

Figure: ATA-4014C High-Voltage Power Amplifier Specifications and Parameters