# A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils

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## Abstract

**:**

## 1. Introduction

## 2. Probe Principle and Assumption

- (1)
- How does an eddy current probe generate an eddy current distribution which can be easily disturbed by defect?
- (2)
- How can an eddy current probe suppress the lift-off noise?
- (3)
- How can an eddy current probe sense the defect signal effectively?

## 3. Experimental Setup

#### 3.1. Eddy Current Probe

#### 3.2. Specimen

#### 3.3. Experimental System

## 4. Result and Discussion

#### 4.1. Contrast Experiment of the Two Probes

_{pp}) of the real part signals of probe A and B are 0.71 V and 0.35 V, respectively, and the V

_{pp}of the imaginary part of probe A and B are 0.51 V and 0.52 V, respectively. Thus, the ${V}_{pp}$ of the real part of probe A is about twice as large as that of probe B, and the V

_{pp}of the imaginary part of probe A is about 1.22 times larger than that of probe B.

#### 4.2. Capability Evaluation Experiment

_{pp}of the real and imaginary parts signal for different depth defect. The two part signals of 5-mm and 10-mm length defects increase approximately as the depth of defect increase. For the each certain defect, the real part of V

_{pp}is larger than the imaginary part. The maximum values of the real and imaginary parts of the 5-mm length defects are 0.376 V and 0.159 V, respectively. Those values of the 10-mm length defects are 0.498 V and 0.294 V, respectively, which are larger than those of the 5-mm length defects.

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Two pickup coils for the two driver traces perpendicular to each other: (

**a**) circular pickup coil, (

**b**) two-circular sector pickup coil.

**Figure 2.**Eddy current disturbance: (

**a**) no disturbance in the circular pickup coil, (

**b**) disturbance in the circular pickup coil, (

**c**) no disturbance in the two-circular sectors pickup coil, (

**d**) disturbance in the two-circular sectors pickup coil.

**Figure 8.**Peak contrast of the signals of two probes: (

**a**) peak-to-peak value, (

**b**) rate of change of peak-to-peak value.

Defect Depth (mm) | Real Part V_{pp} (V) | Imaginary Part V_{pp} (V) |
---|---|---|

0.1 | 0.077 | 0.016 |

0.2 | 0.133 | 0.036 |

0.3 | 0.229 | 0.076 |

0.4 | 0.218 | 0.081 |

0.5 | 0.255 | 0.103 |

0.6 | 0.295 | 0.125 |

0.7 | 0.272 | 0.119 |

0.8 | 0.355 | 0.152 |

0.9 | 0.369 | 0.160 |

1.0 | 0.376 | 0.159 |

Defect Depth (mm) | Real Part V_{pp} (V) | Imaginary Part V_{pp} (V) |
---|---|---|

0.1 | 0.044 | 0.014 |

0.2 | 0.131 | 0.051 |

0.3 | 0.187 | 0.084 |

0.4 | 0.216 | 0.106 |

0.5 | 0.319 | 0.165 |

0.6 | 0.378 | 0.201 |

0.7 | 0.396 | 0.219 |

0.8 | 0.488 | 0.266 |

0.9 | 0.473 | 0.281 |

1.0 | 0.498 | 0.294 |

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**MDPI and ACS Style**

Chen, G.; Zhang, W.; Jin, W.; Pang, W.; Cao, Z.; Wang, K.; Song, Z.
A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils. *Sensors* **2019**, *19*, 4628.
https://doi.org/10.3390/s19214628

**AMA Style**

Chen G, Zhang W, Jin W, Pang W, Cao Z, Wang K, Song Z.
A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils. *Sensors*. 2019; 19(21):4628.
https://doi.org/10.3390/s19214628

**Chicago/Turabian Style**

Chen, Guolong, Weimin Zhang, Wuyin Jin, Weihan Pang, Zheng Cao, Kang Wang, and Zhibo Song.
2019. "A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils" *Sensors* 19, no. 21: 4628.
https://doi.org/10.3390/s19214628