Imperial units

The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments. The imperial system developed from earlier English units as did the related but differing system of customary units of the United States. The imperial units replaced the Winchester Standards, which were in effect from 1588 to 1825. The system came into official use across the British Empire in 1826. By the late 20th century, most nations of the former empire had officially adopted the metric system as their main system of measurement, but imperial units are still used alongside metric units in the United Kingdom and in some other parts of the former empire, notably Canada. The modern UK legislation defining the imperial system of units is given in the Weights and Measures Act 1985 (as

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Model-less Measurement-based Computation of Voltage Sensitivities in Unbalanced Electrical Distribution Networks

Mauro Carpita, Konstantina Christakou, Carl Emile Mugnier, Mario Paolone

Within the context of microgrids optimal voltage control, most schemes proposed in the literature either rely on (i) droop-control methods or (ii) methods involving the computation of explicit nodal power set-points as a solution to a given optimization problem. The first category of approaches is in general suboptimal as it relies on locally sensed measurements. The second category guarantees some level of optimality but requires an accurate and up-to-date model of the network that is, in general, not always available in low voltage grids. To overcome the aforementioned limitations, in this work we propose a methodology suitable for voltage control in generic low voltage 3-phase unbalanced grids. It can be used for the computation of either explicit power set-points or to define the droops of local voltage regulators. Its main characteristic is that it does not rely on the knowledge of the system model and its state. In particular, the goal is to compute linearized dependencies between voltage magnitude and nodal power injections, i.e., voltage sensitivity coefficients. The proposed method assumes availability of a monitoring infrastructure and the computation of the desired sensitivities involves the solution of an over-determined system of linear equations constructed solely using available measurements of nodal power injections and voltage magnitudes. The proposed method is also capable to account for the measurement errors and their time correlation. The performance evaluation of the proposed method is carried out using real measurements coming from a real low voltage feeder located in Switzerland equipped with an appropriate metering infrastructure.

Università degli Studi di Genova, Italy2016

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We propose several processing methods to mitigate the probability of large errors in Chirped-pulse ɸOTDR, improving performances for long-term measurements. For no perturbation applied, we reach a 2 mK error after a 24 h experiment.

2020

Active load cell with positive, negative and zero stiffness operating modes for micronewton range contact force monitoring in electrical probing

Charles Baur, Simon Nessim Henein, Hubert Pierre-Marie Benoît Schneegans, Michal Stanislaw Smreczak

This article describes a novel method for applying a contact force in the range of 1 to 100 μN with pointed probe on a microscale sample in order to perform ohmic electrical measurements. The solution is based on the new TIVOT active load cell combining the functions of a force sensor and an actuator. Probe movement is performed by a piezo actuator which allows the probe tip to be moved over a 5.64 mm range with submicrometric precision. Force measurement is enabled by measuring the elastic deformation of a compliant structure with adjustable stiffness. Strategies are presented to remotely adjust the sensitivity of the mechanism leading to resolutions from 12 μN to 10 nN for forces ranges from 0-60 mN to 0-1 mN respectively. The piezo-actuated stiffness adjustment enables the mechanism to operate in a bistable mode with a tunable maximal threshold force, thus protecting the probe and sample from overloads. Zero offset tuning, in combination with the non-linear characteristic of the mechanism, allows reaching a quasi-constant force characteristic after landing the probe which helps maintaining a stable electrical contact during measurement. Experimental results show that this approach secures and improves probe to sample contact force leading to more efficient measurements than with the traditional methods.

2022

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