Articles you may be interested in Eddy current measurement system evaluation for corrosion depth determination on cast aluminum aircraft structure AIP Conf. Proc. 1511, 1278 (2013); 10.1063/1.4789190Nondestructive evaluation of steel structures using a superconducting quantum interference device magnetometer and a neural network system Rev. Sci. Instrum. 71, 3806 (2000)Imaging and quantitative measurement of corrosion in painted automotive and aircraft structures AIP Conf.Precision sample rotator with active angular position readout for a superconducting quantum interference device susceptometer Rev.We have designed and built a magnetic imaging system for quantitative analysis of the rate of ongoing hidden corrosion of aircraft aluminum alloys in planar structures such as intact aircraft lap joints. The system utilizes a superconducting quantum interference device ͑SQUID͒ magnetometer that measures the magnetic field associated with corrosion currents. It consists of a three-axis ͑vector͒ SQUID differential magnetometer, magnetic, and rf shielding, a computer controlled x-y stage, sample registration, and positioning mechanisms, and data acquisition and analysis software. The system is capable of scanning planar samples with dimensions of up to 28 cm square, with a spatial resolution of 2 mm, and a sensitivity of 0.3 pT/Hz 1/2 ͑at 10 Hz͒. In this article we report the design and technical issues related to this system, outline important data acquisition techniques and criteria for accurate measurements of the rate of corrosion, especially for weakly corroding samples, and present preliminary measurements.

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In this paper, a closed-loop micro-opto-electro-mechanical system (MOEMS) accelerometer based on the Fabry-Pérot (FP) interferometer is presented. The FP cavity is formed between the end of a cleaved single-mode optical fiber and the cross-section of a proof mass (PM) which is suspended by four U-shaped springs. The applied acceleration tends to move the PM in the opposite direction. The arrays of fixed and movable comb fingers produce an electrostatic force which keeps the PM in its resting position. The voltage that can provide this electrostatic force is considered as the output of the sensor. Using a closed-loop detection method it is possible to increase the measurement range without losing the resolution. The proposed sensor is fabricated on a silicon-on-insulator wafer using the bulk micromachining method. The results of the sensor characterization show that the accelerometer has a linear response in the range of ±5 g. In the closed-loop mode, the sensitivity and bias instability of the sensor are 1.16 V/g and 40 µg, respectively.