La Babel de los sistemas de medida : la unificación del sistema de medida dimensional es imitado por la unificación del sistema monetario

Peer Reviewe

Uncertainty analysis in two-terminal impedance measurements with residual correction

Residual impedance correction in impedance analyzers when using an asymmetrical test fixture needs three reference measurements, usually open circuit, short circuit, and load (meaning an impedance close to the impedance under test). This paper provides an uncertainty estimate for impedance measurements that apply a simple open/short correction in spite of using an asymmetrical test fixture. Experimental results show that the minimal uncertainty is obtained for impedance values close to the geometric mean of the short-circuit and open-circuit impedances, and that the theoretical prediction is indeed an upper limit for the actual uncertaintyPeer Reviewe

Error analysis in two-terminal impedance measurements with residual correction

Residual impedance correction in impedance analyzers when using an asymmetrical test fixture needs three reference measurements, usually open circuit, short circuit, and load (meaning an impedance close to the impedance under test). This paper provides an error estimate for impedance measurements that apply a simple open/short correction in spite of using an asymmetrical test fixture. Experimental results show that the minimal error is obtained for impedance values close to the geometric mean of the short-circuit and open-circuit impedances, and that the theoretical prediction is indeed an upper limit for the actual error.Peer Reviewe

Compensation of impedance meters when using an external front-end amplifier

Four-terminal impedance meters based on pseudo-bridges yield unexpected uncertainties when using high-contact-impedance electrodes. Adding a front-end amplifier to the impedance meter and rearranging the connection of the meter terminals overcome the contact impedance problem. However, because the compensation provisions in the instrument are meant to compensate only impedance residuals of test fixtures, by either an open/short or an open/short/load correction procedure, the external front-end increases the inaccuracy of the measurement setup. This paper shows that an open/short/load correction can also compensate complicated impedance residuals such as those from external amplifiers. The paper details the correction procedure and provides the equations to calculate the impedance under test from the readings of the impedance meter.Peer Reviewe

Method for forming a magnetic field of arbitrary shape from an established template

A strategy to design a particular form of magnetic field along an axis from a coaxial inductor is described. The procedure is illustrated with the design of a constant magnetic field inside a cubic inductor. It validates the goodness of the method by comparing the results with all possible combinations of inductance within a limited set of solutions.Peer ReviewedPostprint (published version

Electrical impedance as a technique for civil engineer structures surveillance : considerations on the galvanic insulation of samples

Since Electric Impedance Spectroscopy (EIS) has been widely used to determine physical properties of materials, it becomes necessary to evaluate different error contributions. In this work, it is studied the effect of the current leakage due to the lack of galvanic insulation from sample to ground, which could distort the results. In order to known the effects of ground coupling, an electric equivalent model is developed to distinguish between the contribution of the sample impedance and the stray impedance one. Model values agree with measured ones.Peer Reviewe

Method for forming a magnec field of arbitrary shape from an established template

A strategy to design a particular form of magnetic field along an axis from a coaxial inductor is described. The procedure is illustrated with the design of a constant magnetic field inside a cubic inductor. It validates the goodness of the method by comparing the results with all possible combinations of inductance within a limited set of solutions. Keywords: Magnetic field, magnetic sensor, Helmholtz coils.Peer ReviewedPostprint (published version

Evaluation of conductive concrete made with steel slag aggregates

The incorporation of black steel slag (waste from steel production) in concrete responds to a greater awareness of sustainability. In addition, it is capable of increasing electrical conductivity. The objective of this work is to achieve multifunctional concretes with higher mechanical performance and which can modify the electrical characteristics. In this work, natural aggregates have been replaced by different aggregates of steel slags from Spanish industries and the mechanical characteristics of compression, modulus of elasticity, indirect traction and electrical characteristics of these concretes have been studied with respect to reference mixtures. Encouraging results have been obtained for concrete with slag and metallic fibers, improving the electrical conductive capacity by almost 70% and improving the mechanical performance by 14%.The authors acknowledge the financial support provided by the project PID2019-106555RB-I00. The first author acknowledges the financial support from Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR), with the doctoral fellowship: Personal investigador novell (FI) 2021. We would also like to thank the following companies: Promsa, Sidenor, Calcinor, Hormor and Adec for supplying the slag, without which this study would not be possible.Peer ReviewedPostprint (published version

Subsurface resistivity measurements using square waveforms

This work analyzes the effect of inductive and capacitive coupling between the injecting circuit and the detecting circuit in resistive field surveys. Theoretical and experimental results demonstrate that if a square waveform is injected into the soil, and synchronous sampling is used to sample at the flat zone of the detected voltage, then the effect of the interference is greatly reduced. Furthermore, square waveforms are easier to generate than sinusoidal waveforms, so they offer a new approach to subsurface resistivity measurements.Peer Reviewe

The floating capacitor as a differential building block

This paper analyzes the advantages and limitations of using the floating- (or flying-) capacitor technique as a building block with differential input and either differential or single-ended output to implement voltage amplifiers, multiplexers, and coherent amplitude demodulators. Theoretical analysis, supported by experimental results, shows that the fully differential configuration has a better common-mode rejection ratio (CMRR). However, if the output signal, once amplified, must be single ended, then it may be better to have a floating capacitor with single-ended output in amplifiers and some multiplexers whereas in demodulators a floating capacitor with differential output yields a better CMRR.Peer Reviewe