Eddy current sensor

Progress in mean of modelisation and inverse problem solving [1] let us hope to dispose soon of these tools for flaws 3D imaging in Non Destructive Control with eddy current sensors. This will achieve a real improvement of the actual methods, mainly based upon signature analysis. But the actual eddy current probes used for steam generators tubes inspection in nuclear industry do not produce the adequate measurements and/or are not modelisable. 

D. Miller, D.Placko "Pre-processing of signals delivered by a new eddy current sensor for non ferromagnetic tubes testing" in IMTC 96... 

The advent of new, more reliable, and sensitive vibration instrumentation such as the eddy-current sensor and the accelerometer coupled with modern... 

In conventional CMP, end-point detection relies on in situ sensors such as eddy current sensors [26] to measure the remaining copper film thickness. In... 

These requirements comply with the performance of a device consisting of a piezo-driven actuator and an Eddy-current sensor that measures the displacement. The miniaturized closed loop system is being built and tested at CESR and ANL. 

Brake clearance L (4 groups) Skin temperature of brakes (4 groups) High-frequency eddy current sensor Infrared temperature sensor Sensor installed on the brake block, surface parallel to the brake shoe back... 

Liqun Wang 2004. Monitoring method of the disc brake clearance based on eddy current sensors. Coal Mine Machinery 122-123. 

ABSTRACT Eddy current sensors are well-established in industrial appheations, such as in hot testing of rolled rods. However, the eddy current sensors currently in use are not able to detect longitudinal cracks in hod rolled rods. This paper introduces a 3D eddy current model which allows an investigation of this particular problem. Generally, 3D eddy current Finite Element Analysis (FEA) are time consuming due to the fine mesh as a result of the small penetration depth of the currents. The introduced 3D FEA model calculates the complex coil impedance of a detection coil affected by a rod with cracks using the current sheet approximation with additional correction formulas. 

The finite element method is already estabhshed in modelling for eddy current sensors the same as analytical methods. For example, reference [1] solves for the absolute impedance of core-less coils, and [2], [3] solve for the induced voltage in the coil. The problem with these analytical models is the dependency on the crack size, shape and location, and the equations needs to be modified all the time. Consequently, the results may not necessarily be comparable. When the FEA is used instead, the results remain comparable for changed model parameters. Hence, the aim of this study is to build a 3D model to calculate the complex coil impedance for encircling coils that measure rods with any kind of cracks. In doing so, two main simplifications are applied as follows. 

U. Trdltzsch, F. Wendler, and O. Kanoun, Simplified analytical inductance model for a single turn eddy current sensor, Sensors and Actuators A Physical, vol. 191, pp. 11-21, 2013. 

Washabaugh, A. Zilberstein, V. Schhcker, D. Shay, I. Grundy, D. and Goldfine, N. Shaped-Field Eddy-Current Sensors and Arrays. SPIE Vol. 4702 (2002), pp. 63-75... 

Electrical resistivity (often expressed through the inverse value—conductivity) and its variations describe the properties of various metals and alloys [1], but also tissues and living bodies, characterized by the bio-impedance [2]. Electrical conductivity can be measured in the contact-less way by eddy current sensor(s), e.g. by using the measurement setup with a single measurement coil above the measured object, which can be a metal plate, for example, as described analytically [3] or numerically [4, 5]. Experiments show reasonable similarity between the real measurements and theoretical models. 

A few years ago, a major adhesives manufacturer collaborated with an auto company to develop a novel method for controlling the mix ratio of two-part epoxy adhesives. They discovered that the mix ratio can be continuously measured via a tagging system that incorporates microscopic stainless steel-coated glass bubbles in one component of the adhesive. The bubbles are detected by two eddy current sensors integrated into the dispensing equipment. This technique enables 100% knowledge and control of the dispense ratio. 

The MWM is a planer, confomiiable eddy current sensor designed to suppot quantitative and autono-... 

---