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Technology of electrical measurements
... In this case, the noise suppression is (see e.g., [10]) ...
A nonparametric identification method for linear systems is proposed. The identification is done via synchronized multisine measurements where the synchronization is ensured by a resonator-based generator-observer pair. The advantage of the proposed structure is that it works as a filter bank and, hence, provides the measurement results online. Exponential averaging is an option of the method and it requires no extra calculations. A further advantage is that the identification can be done over any frequency set without any loss of performance. Explicit formulas are given for noise suppression and settling time. The method is illustrated by practical examples.
... Students who have only experimented with routine and more standardized procedures often become " blocked " because well-defined, step practices are generally unsuited to solve open-ended problems. Measurements are always a part of the model-creating process, as it is apparent to professional engineers [2]. Explicit awareness of this relationship can improve students' understanding of real-world engineering problems. ...
A laboratory experiment for the introductory electrical circuit course is presented. The experiment consists of the measurement of real commercial capacitors' impedance using a relatively low-cost impedance meter, and further analysis on two levels. First, when results follow well the conventional impedance expression of an ideal capacitor, the capacitance can be determined accurately. Second, when deviations are found, the more advanced framework of equivalent circuit representation has to be used. This representation is discussed for the particular case of capacitors with DC leakage. This experimental approach explicitly emphasizes the role of electrical models in engineering and suggests how to use instrumentation to validate them.
Vector Network Analyzers (VNA) measure tested circuits in the
frequency domain but their frequency range does not include DC. When
VNAs are used for time-domain measurements, the proper transformation
requires the measured DC value as well. Under certain conditions
extrapolation of the DC response can be incorrect, which causes
incorrect time domain response, too. This paper presents a solution to
this problem
Switching power converters are an indispensable part of every battery-operated consumer electronic product, nourishing regulated voltages to various subsystems. In these circuits, sensing the inductor current is not only necessary for protection and control but also is critical to be done in a lossless and accurate fashion for state-of-the-art advanced control techniques, which are devised to optimize transient response, increase the efficiency over a wide range of loads, eliminate off-chip compensation networks, and integrate the power inductor. However, unavailability of a universal, integrable, lossless, and accurate current-sensing technique impedes the realization of those advanced techniques and limit their applications. Unfortunately, use of a conventional series sense resistor is not recommended in high-performance, high-power switching regulators where more than 90% efficiency is required because of their high current levels. A handful of lossless current-sensing techniques are available but their accuracies are significantly lower than the traditional sense resistor scheme. Among available lossless but not accurate techniques, an off-chip, filter-based method that uses a tuned filter across the inductor to estimate current flow and its accuracy is dependent on the inductance and its equivalent series resistance (ESR) was selected for improvement because of its inherent continuous and low-noise operation. A schemes is proposed to adapt the filter technique for integration by automatically adjusting bandwidth and gain of an on-chip programmable gm-C filter to the off-chip power inductor during the system start-up through measuring the inductance and its ESR with on-chip generated test currents. The IC prototype in AMI s 0.5-um CMOS process achieved overall DC and AC gain errors of 8% and 9%, respectively, at 0.8 A DC load and 0.2 A ripple currents for inductors from 4 uH-14 uH and ESR from 48 mOhm to 384 mOhm when lossless, state-of-the-art schemes achieve 20 40% error and only when the nominal specifications of power component (power MOSFET or inductor) are known. Moreover, the proposed circuit improved the efficiency of a test bed current-mode controlled switching regulator by more than 2.6% at 0.8 A load compared to the traditional sense resistor technique with a 50 mOhm sense resistor. Ph.D. Committee Chair: Rincon-Mora, Gabriel; Committee Member: Divan, Deepakraj; Committee Member: Habetler, Thomas G; Committee Member: Harrell, Evans; Committee Member: Leach, W Marshall
A self calibrated BIST methodology is proposed to overcome the process variation of the BIST circuitry. Two test methods are proposed, one by statistical analysis and another by curve fitting. Test hardware is built by discrete components to emulate the ADC BIST circuitry. Experimental results verify the feasibility of the methodology.
In frequency domain system identification, the Fourier coefficients and their variances are used to calculate the estimated parameters. They are calculated from the measured signals. Therefore, good estimation of the Fourier coefficients and of their variance is utmost importance. It is a common practice to segment the periodic signal into periods, calculate the Fourier coefficients in each period, average them, and perform variance analysis, too. Here an important questions arises: do we use all the information present in the signal? Can we improve this procedure? This paper analyzes the information utilization in the process, examines when is it optimal, explains when processing of overlapped segments can help and why, and suggests an improved preprocessing procedure, increasing the quality of the calculated Fourier coefficients.
This paper presents a theoretical analysis of error calculations
during a system design. A system is understood as a measurement chain
that consists of units called transducers. In general, transducers are
connected in three basic configurations; serial, parallel and with
feedback. In order to illustrate the analysis of error calculations we
consider only two connected units for each configuration of a
measurement chain. In this paper, we analyze two types of error
calculations for these three basic configurations. First, a standard
error calculation is described assuming that transducer errors in a
measurement chain are mutually correlated. System designers frequently
assume an error correlation and therefore use standard error
calculations. Second, error calculations are performed assuming that
transducer errors are not mutually correlated. The case of mutually
uncorrelated transducer errors is very common in a real system design
since the numerical specifications of individual transducers are
obtained from multiple independent catalogs. Thus, it is the
uncorrelated nature of transducer errors that requires a modification of
standard error calculations. We analyze error calculations for each
configuration of transducers and for mutually correlated and
uncorrelated transducer errors. In conclusion, the error formulas
assuming mutually uncorrelated transducer errors model a real system
design more accurately than the standard error formulas
A nonparametric identification method for linear systems is
proposed. The identification is done via synchronized multisine
measurements where the synchronization is ensured by a resonator based
generator-observer pair. The advantage of the proposed structure is that
it works as a filter bank and provides the measurement results on-line.
Exponential averaging is an option of the method and it requires no
extra calculations. A further advantage is that the identification can
be done over any frequency set without any loss of performance. Explicit
formulas are given for noise suppression and settling time. The method
is illustrated by a practical example
The classical “frequency sampling method” (1975) based
on the direct utilization of the Lagrange interpolation technique is
extended in a natural way to a rather efficient Hermite interpolation
scheme. This structure is a new extension related to the resonator-based
digital filter family introduced by M. Padmanabhan et al. (1996). The
development resulted in a system having good properties if measurement
of signals consisting of sinusoidal components is to be performed
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