E. Romeo

A Smart THD Meter Performing an Original Uncertainty Evaluation Procedure

In this paper, the authors deal with a smart total harmonic distortion (THD) meter that is able to determine the uncertainty of the measurements that it executes. Such an instrument, which is used for power quality monitoring through the measure of an index, acquires the signal samples from the low-voltage network and evaluates the THD factor. To estimate the uncertainty associated with this last result, a theoretical characterization of the whole instrument realized according to the International Organization for Standardization Guide recommendations (transducer stage included) is discussed first. This approach application has proved to be very useful to justify the necessity of looking for an alternative technique. Therefore, the authors proposed the ldquogrey boxrdquo calibration procedure. Considerations about the comparison of the two procedures have been made.

The Implementation of an Automatic Measurement Station for the Determination of the Calibration Intervals for a DMM

In the present work the authors present a procedure for the determination of the optimal calibration intervals of a measurement instrument according to the reference Standard. Generally speaking, the goal of a calibration process is to reduce out-of tolerance occurrences to an acceptable level with respect to the desired quality target. The approach is based on the monitoring of the capability of an instrument in making measurements in conformity with the accuracy declared in the datasheet provided by the manufacturer. Periodic actions are required for the metrological confirmation, effected in a laboratory of tests, using for this purpose a reference instrument. In this paper is presented the implementation of an automatic station of measurement which performs an original procedure able to forecast the time to wait for the next calibration process

Implementation of multiple decision rules using random-fuzzy variables based on Yager's t-norm

Though standards regarding metrological confirmation contain all requirements an organization has to satisfy to guarantee that measurements are performed with the desired accuracy level, nothing is said about multiple decision rules occurrences. In this paper we propose to use an approach with random-fuzzy variables based on Yager t-norm for proving conformance or non conformance with specifications for a desired level of confidence in the event the measurement algorithm contains multiple comparisons.

A Fuzzy Approach to represent Measurement Data affected by both A-type and B-type Uncertainty

This paper proposes a new approach to transform the probability distribution of N repeated measurement results into a possibility distribution in presence of both A-type and B-type uncertainty. The technique presents the final measurement result in terms of a fuzzy set which easily expresses the levels of confidence for the final uncertainty to be determined as a-cuts. In this treatment the statistical independence of the measurement data permit the assumption that the samples are derived from a normal distribution. The fuzzy set representation of measurement uncertainty is preferable in cases where acquisitions have to be further processed and where, in these events, a conversion into symbolic format may be also necessary reasoning systems. As a case study, the propagation of uncertainty in presence of decision rules is considered

Uncertainty Evaluation of a THD Meter based on FPGA platform

In this paper we propose an instrument for the power quality monitoring, through the measure of PQ indexes (in particular we refer in this work to the THD index meter) and its characterization. The realized instrument is able to acquire the signal samples (opportunely conditioned) from the power network, to calculate the THD index and to estimate the uncertainty by which the last result is affected. The implementation makes use of a FPGA (field programmable gate array) Xilinx Virtex-II programmed in VHDL. This electronic device is a valid solution to speed, dissipated power and costs problems, and may be revisited every time the algorithm it implements becomes too obsolete (e.g. when new PQ indexes need to be substituted for old ones) or when one wants (for different needs) vary even one parameter of the structure. The utilized development system traduces the code (VHDL is a universal and highly compatible programming language) into the circuital specification that the platform has to assume

A Distributed Measurement System for the Evaluation of the Safety State in Highway Tunnels

This paper presents a distributed smart system for evaluating the safety state in highway tunnels. This system will alert all vehicles passing trough the monitored tunnel that a dangerous state has been detected, such as a fire or the presence of injurious vapors which might possibly ignite. The system implements original and innovative data fusion algorithms in two-stages, based on the creation of decisional fuzzy rules built on linguistic variables in presence of measures affected by uncertainty. The distributed network of sensing devices and thermal vision system monitor continuously the tunnel environment, permitting extraction of information on the safety state of tunnel. If the system finds an effective anomaly, and the sensors and the cameras are working accurately, a message is sent to inform the drivers about the exact location of the danger. In fact, by using the RF technology of communication, the vehicle is able to recognize its own position within the tunnel and the distance separating it from the critical area detected.

Calibration of Virtual Instruments based on Random-Fuzzy approach

In this paper, we proposed a technique based on random fuzzy approach for the calibration of a virtual instrument (VI). This technique is based on Yager triangular norm and is used to describe measurement uncertainty (both random and systematic effects, as seen in (Urbanski and Wasiwsky, 2003)) in a simple and quite fast way. The whole measurement chain is not totally treated as a black box, because manufacturers specifications for conversion and transducer system are used to determine the uncertainty propagation in measurements performed by the VI of (De Capua et al., 2004)