Magnetic Sensor Angle Adjustment to Improve Corrosion under Insulation Detection.

A large portion of the pipe infrastructure used in the chemical processing industry is susceptible to corrosion under insulation (CUI). Eddy current-based magnetic sensing is one of the methods that can be used as an early detector of this corrosion. However, the large sensor-to-pipe distances used in this method, due to the presence of insulation, limits the sensitivity to corrosion. This paper will describe the development of instrumentation and methods based on eddy current sensing with thin-film magnetic sensors. In particular, it focuses on the influence of the sensor angle relative to the radial magnetic field. The influence of this parameter on the amplitude of the measured signal was investigated by both finite element simulations and experimental observations. The measured magnetic field was found to be highly sensitive to small changes in sensor angle, with the estimated depth of a defect changing at a rate of 11.2 mm/degree of sensor rotation for small angles. It is also shown that a sensor aligned with the radial direction should be avoided, with an optimal sensor angle between 0.5 and 4 degrees. With the sensor in this angle range, the simulations have shown it should be possible to resolve the depth of corrosion to a resolution of 0.1 mm.

Synthesis of encapsulated ZnO nanowires provide low impedance alternatives for microelectrodes.

Microelectrodes are commonly used in electrochemical analysis and biological sensing applications owing to their miniaturised dimensions. It is often desirable to improve the performance of microelectrodes by reducing their electrochemical impedance for increasing the signal-to-noise of the recorded signals. One successful route is to incorporate nanomaterials directly onto microelectrodes; however, it is essential that these fabrication routes are simple and repeatable. In this article, we demonstrate how to synthesise metal encapsulated ZnO nanowires (Cr/Au-ZnO NWs, Ti-ZnO NWs and Pt-ZnO NWs) to reduce the impedance of the microelectrodes. Electrochemical impedance modelling and characterisation of Cr/Au-ZnO NWs, Ti-ZnO NWs and Pt-ZnO NWs are carried out in conjunction with controls of planar Cr/Au and pristine ZnO NWs. It was found that the ZnO NW microelectrodes that were encapsulated with a 10 nm thin layer of Ti or Pt demonstrated the lowest electrochemical impedance of 400 ± 25 kΩ at 1 kHz. The Ti and Pt encapsulated ZnO NWs have the potential to offer an alternative microelectrode modality that could be attractive to electrochemical and biological sensing applications.

Mobile low field magnetic resonance hardware development.

Typically, NMR systems are bulky and expensive laboratory based equipment. For half a century after its scientific discovery taking NMR outside of a laboratory environment is still not a common practice due to the complexity of the underlining physical phenomena and its low sensitivity, to the myriad of technical challenges when integrating a complete system. The scarcity of compact and mobile NMR systems has prevented its proliferation into many other areas and applications. This paper describes the progress in the development of compact electronic spectrometers that we coupled with handheld sensors in order to provide complete mobile solutions. The key to this progress has been the modern advances in computing, electronics and permanent magnet technologies. Mobile NMR is now feasible as a valuable, non-invasive tool for industrial and medical applications. By leveraging the strengths of NMR, which is to probe at the molecular level and gain information about molecular structure, organisation, abundance and orientation, NMR is intrinsically suitable for non-destructive testing of a wide range of materials and their manufacturing processes. The development of complete NMR systems benefits from working across various disciplines and organisations. By embracing a collaborative approach we believe it will accelerate NMR technology to become more ubiquitous in the near future.

A temperature compensated dielectric test cell for accurately measuring the complex permittivity of liquids.

A measurement of the complex permittivity, εr, of a liquid can give valuable information about the molecular polarizability and dielectric losses. This can be obtained by means of an impedance measurement using a parallel plate test cell. However, highly accurate and precise measurements are challenging, in particular when measuring as a function of temperature. Thermal expansion affects the geometry of a test cell and thus the measured capacitance from which εr is calculated. In this paper, a broadband four-terminal dielectric test cell is presented that is insensitive to temperature fluctuations. This was achieved by means of a cell geometry exploiting the thermal expansion coefficient of different materials. Experimental measurements on the manufactured cell yielded a stable capacitance of 35.322 ± 0.001 pF across 20 °C-90 °C. The capacitance stayed within ±0.01 pF over multiple experimental cycles of cleaning and assembly. A finite element modeling showed a theoretical accuracy in measuring εr better than 99.995%. The measured εr values for a number of standard liquids showed an agreement of 99.7% compared to literature values.

A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance.

Interdigitated dielectrometry sensors (IDS) are capacitive sensors investigated to precisely measure the relative permittivity ( ϵ r ) of insulating liquids. Such liquids used in the power industry exhibit a change in ϵ r as they degrade. The IDS ability to measure ϵ r in-situ can potentially reduce maintenance, increase grid stability and improve safety. Noise from external electric field sources is a prominent issue with IDS. This paper investigates the novelty of applying a Faraday cage onto an IDS as a 3D shield to reduce this noise. This alters the spatially distributed electric field of an IDS affecting its sensing properties. Therefore, dependency of the sensor's signal with the distance to a shield above the IDS electrodes has been investigated experimentally and theoretically via a Green's function calculation and FEM. A criteria of the shield's distance s = s 0 has been defined as the distance which gives a capacitance for the IDS equal to 1 - e - 2 = 86.5 % of its unshielded value. Theoretical calculations using a simplified geometry gave a constant value for s 0 / λ = 1.65, where λ is the IDS wavelength. In the experiment, values for s 0 were found to be lower than predicted as from theory and the ratio s 0 / λ variable. This was analyzed in detail and it was found to be resulting from the specific spatial structure of the IDS. A subsequent measurement of a common insulating liquid with a nearby noise source demonstrates a considerable reduction in the standard deviation of the relative permittivity from σ unshielded = ± 9.5% to σ shielded = ± 0.6%. The presented findings enhance our understanding of IDS in respect to the influence of a Faraday shield on the capacitance, parasitic capacitances of the IDS and external noise impact on the measurement of ϵ r .

Anisotropic microstructured poly(vinyl alcohol) tissue-mimicking phantoms.

Novel microstructured PVA phantoms mimicking fibrous tissues have been developed using a simple freeze-casting process. Scanning electron micrographs reveal highly anisotropic microstructure with dimensions of the order of 5 to 100 microm. Characterization of an example phantom revealed acoustic properties consistent with those found in fibrous tissues. At 20 MHz, the velocity measured parallel to the microstructure orientation of 1555 ms(-1) was significantly greater than that perpendicular to the microstructure of 1537 ms(-1). The attenuation coefficient was measured to be 5 dBxmm(-1) and proportional to the 1.6 power of frequency, which is in good agreement with that for normal human myocardium.