비파괴검사학회지 (Journal of the Korean Society for Nondestructive Testing)

  • 제26권2호
  • /
  • Pages.99-107
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  • 2006
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  • 1225-7842(pISSN)
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  • 2287-402X(eISSN)
한국비파괴검사학회 (The Korean Society for Nondestructive Testing)
권호 표지

마이크로프로세서를 이용한 자기카메라 전용 임베디드형 AD 변환기 및 잡음 감소에 관한 연구

A Study of the Exclusive Embedded A/D Converter Using the Microprocessor and the Noise Decrease for the Magnetic Camera

  • 발행 : 2006.04.30
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⟨ 이전 논문 다음 논문 ⟩

초록

자기적인 방법을 이용한 비파괴검사는 강자성체 표면 및 표면 근방의 균열을 탐상하는데 매우 유용하다. 균열을 평가하기 위해서는 시험편상의 누설자속분포를 정량적으로 취득해야 한다. 자기카메라는 큰 리프트오프에서 누설자속분포를 얻기 위하여 제안되었다. 자기카메라는 지원, 자기렌즈, AD 변환기, 인터페이스 및 컴퓨터로 구성되어 있다. 측정 대상체로부터 누설된 자속 또는 흐트러진 자장은 지기렌즈로 집속된 후, 배열된 작은 지기센서에 의하여 아날로그신호로 변환된다. 이러한 아날로그 신호는 AD 변환기에 의하여 디지털신호로 변환되고, 인터페이스 및 컴퓨터에 의하여 저장, 영상화 및 처리된다. 그러나, 지급까지의 자기카메라는 범용 AD변환기를 사용하기 때문에 변환 및 스위칭속도, 검출범위 및 분해능, 직접 메모리 액세스(DMA, direct memory access), 임시저장속도 및 저장량에 한계점을 가지고 있었다. 또한, S/N비를 높이기 위하여 OP-AMP의 도입, 신호의 증폭, 배선의 감소, LPF의 사용과 팥은 개선된 기술이 필요하다. 본 논문은 상술한 조건들을 만족하기 위하여 OP-AMP, LPF, 마이크로프로세서 및 DMA 회로를 포함한 자기카메라 전용 임베디드형 AD 변환기를 제안한다.

Magnetic nondestructive testing is very useful far detecting a crack on the surface or near of the surface of the ferromagnetic materials. The distribution of the magnetic flux leakage (DMFL) on a specimen has to be obtained quantitatively to evaluate the crack. The magnetic camera is proposed to obtain the DMFL at the large lift-off. The magnetic camera consists of a magnetic source, magnetic lens, analog to digital converters (ADCs), interface, and computer. The magnetic leakage fields or the distorted magnetic fields from the object, which are concentrated on the magnetic lens, are converted to analog electrical signals tv arrayed small magnetic sensors. These analog signals are converted to digital signals by the ADCs, and are stored, imaged, and processed by the interface and computer. However the magnetic camera has limitations with respect to converting and switching speed, full range and resolution, direct memory access (DMA), temporary storage speed and volume because common ADCs were used. Improved techniques, such as those that introduce the operational amplifier (OP-Amp), amplify the signal, reduce the connection line, and use the low pass filter (LPF) to increase the signal to noise ratio are necessary. This paper proposes the exclusive embedded ADC including OP-Amp, LPF, microprocessor and DMA circuit for the magnetic camera to satisfy the conditions mentioned above.

키워드

참고문헌

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