Inductive sensor

About: Inductive sensor is a research topic. Over the lifetime, 2282 publications have been published within this topic receiving 21984 citations.

A differential transformer-based force sensor utilizing a magnetic fluid core

Abstract: A force sensor utilizing a transformer concept with a ferrofluid core was developed. A ferrofluid reservoir was machined out of Teflon and the open top of the reservoir was sealed with a thin silicone membrane. Forces applied to the silicone membrane caused the membrane to deflect, resulting in the displacement of the ferrofluid in the reservoir through an external tube. The ferrofluid in the tube acted as the core of voltage transformer. The ferrofluid core was excited by an alternating current across a wire coil wound around the tube. A secondary coil was wound around the top portion of the tube which was vertically oriented. As the ferrofluid level in the tube rose in response to applied forces, the secondary coil became engaged by the magnetized ferrofluid, resulting in a voltage induced in the secondary coil that varied with the level of the ferrofluid. The sensor was characterized by the relationship between the forces applied to the membrane and the output voltage readings across the secondary coil in loading and unloading cycles. This relationship was found to be nonlinear and following a negative second-degree polynomial relationship. The sensor was tested at three primary frequencies of 60, 100 and 120 kHz. It was found that 13% of the 5 V A/C exciting voltage applied across the primary coil at 60 kHz was induced into the secondary coil when it was fully engaged by the magnetized ferrofluid. It was determined that the sensor generates the highest sensitivity of 68.3 mV/N over the effective range of 0.1–2.5 N at 60 kHz. The sensor was analyzed for error and the characteristic error was found to be comparable to existing inductive sensors. Sources of most significant of error were identified and proposals for improvements to future designs of this sensor type are provided.

Contactless hand tremor detector based on an inductive sensor

Abstract: Using inductive sensing, a contactless tremor detector is presented for evaluating exercise induced hand tremors either after exercise or due to Parkinson's disease. The device consists of spiral coil, microcontroller and inductive sensor circuitry. Calculation shows that resonant frequencies of the circuitry increase when the distances between the hand and the spiral coil decrease. A mechanical hand to imitate hand tremors at a fixed frequency was built for experiments. The magnitudes and frequencies of the tremors in the mechanical hand were quantitatively identified using the inductive sensor. Feasibility and accuracy of the contactless hand-tremor detector were validated. A triaxial accelerometer device was used for comparison. The inductive sensor performed better than the accelerometer comparing spectral distributions and magnitudes of the tremors. The contactless hand-tremor detector can be applied as a clinical instrument for diagnostics.

An Implementation Method for an Inductive Proximity Sensor with an Attenuation Coefficient of 1

Abstract: In order to achieve long-distance measurement, a bridge differential inductance detection circuit is employed; on this basis, an automatic zero adjustment technique for sensors using an integral–proportional-integral controller is proposed in this work to achieve consistent product production and efficient installation and debugging, and the mathematical model of the bridge differential inductance detection circuit is established to effectively design the controller parameters. Furthermore, an implementation method for an inductive proximity sensor with an attenuation coefficient of 1 is also proposed based on the bridge differential inductance detection circuit by querying the proximity distance table in the field-programmable gate array (FPGA) to detect multiple target metal objects at the same inductive distance. Simulation and experimental results show that the proposed method is correct and effective.

Flat type thick film inductive sensors

Abstract: Two thick film flat-type inductive sensors are described and tested for distance and profile measurement. The first one is a single-layer spiral while the second one is a multi-layer structure consisting of ten spirals one over the other. The paper describes their geometric configurations together with their simulated magnetic fields and it reports the results from the characterization test i.e. the series-equivalent circuit parameters, the sensitivity and the cross-sensitivity to temperature. An experimental analysis of the sensitivity suggests that optimized values are obtained by an appropriate choice of the working frequency. The sensors are shielded against e.m. noise coming from the nonsensitive area. Moreover, two sensors have been tested in the laboratory using the single layer as a distance sensor and the multi-layer as a transducer for the measurement of a metallic object profile. The results of the tests show a maximum sensitivity of 14 mV=mm and a resolution of 0.6mm for the single layer, while the multi layer one reconstructs the profile with an axial resolution of a few microns and a lateral resolution better than 200mm.

Impact evaluation of environmental and geometrical parasitic effects on high-precision position measurement of the LHC collimator jaws

Abstract: Measuring the apertures of the Large Hadron Collider (LHC) collimators, as well as the positions of their axes, is a challenging task. The LHC collimators are equipped with high-precision linear position sensors, the linear variable differential transformers (LVDTs). The accuracy of such sensors is limited by the peculiar parasitic effect of being rather sensitive to external magnetic fields. A new type of inductive sensor, the Ironless Inductive Position Sensor (I2PS), that keeps the advantages of the LVDTs but is insensitive to external magnetic fields has been designed, constructed, and tested at CERN. For this sensor, a detailed description of parasitic effects such as high-frequency capacitances and the presence of conductive shields and electric motor, in the surroundings is given, from analytical, numerical, and experimental viewpoints. In addition, proof is given of the I2PS's radiation hardness. The aim of this paper is to give a complete and exhaustive impact evaluation, from the metrological viewpoint, of these parasitic effects on these two fundamental sensor solutions.