Gerard N. Stenbakken

Test-point selection and testability measures via QR factorization of linear models

An efficient algorithm is presented for selecting test points for use in applications such as calibration and fault diagnosis of electronic networks. The algorithm, based on QR factorization of the circuit sensitivity matrix, minimizes the prediction or estimation errors which result from random measurement error. A definition of testability based on the concept of minimum estimation error is also introduced. Practical examples are given.

Developing linear error models for analog devices

Techniques are presented for developing linear error models for analog and mixed-signal devices. A simulation program developed to understand the modeling process is described, and results of simulations are presented. Methods for optimizing the size of empirical error models based on simulated error analyses are included. Once established, the models can be used in a comprehensive approach for optimizing the testing of the devices. Models are developed using data from a group of 13-b analog-to-digital converters and are compared with the simulation results. >

LINEAR ERROR MODELING OF ANALOG AND MIXED-SIGNAL DEVICES

Techniquesare presented for developinglinear error models for analog and mixed-signal devices. Methods for choosingparameters and assuring the models are complete and wellconditioned, are included. Once established, the models can be used in a comprehensive approach for optimizing the testing of the subject devices.

Time-base nonlinearity determination using iterated sine-fit analysis

A new method is presented to determine the time-base errors of sampling instruments. The method does not require a time-base error model and thus provides accurate estimates where model-based methods fail. Measurements of sinewaves at multiple phases and frequencies are used as test signals. A harmonic distortion model is used to account for amplitude nonlinearity of the sampling channel. Use of an independent method for estimating the channel noise and jitter allows an accurate estimate of the harmonic order. Methods are presented for separating the harmonics generated by the sampling channel from those generated by the time-base distortion. The use of an iterative sine-fit procedure gives accurate results in a short time. A new weighting procedure is described, which minimizes the error in the estimates. Guidelines are given for selecting good sets of test frequencies. Results are shown for both simulated and real data.

High-accuracy sampling wattmeter

A high-accuracy sampling wattmeter was developed to investigate the feasibility of using waveform sampling techniques for making very accurate power measurements at frequencies from 50 Hz to 1000 Hz. The goal was to build an instrument with an uncertainty of less than +or-50 ppm over these frequencies. The new wattmeter uses 16-b converters and includes a two-stage current transformer in one of the modules. This wattmeter operates with asynchronous sampling. High-accuracy is achieved by approximately synchronizing the interval over which samples are taken with the period of the input signal. Special care was taken to design input stages with a flat frequency response and low temperature sensitivity. The wattmeter has been calibrated using an audio-frequency power bridge. The two instruments agreed to better than +or-50 ppm of full scale over the 50 Hz to 1000 Hz frequency range at all power factors. The use of an RC attenuator for the voltage scaling proved to be marginal in frequency response for the 240 V range. >

A fast pulse oscilloscope calibration system

A system is described for calibrating high-bandwidth oscilloscopes using pulse signals. The fast-pulse oscilloscope calibration system (FPOCS) is to be used to determine the step response parameters for digitizing oscilloscopes having bandwidths of /spl sim/20 GHz. The system can provide measurement traceability to standards maintained at the U.S. National Institute of Standards and Technology (NIST). It comprises fast electrical step generation hardware, a personal computer (PC) and software, and a reference waveform, i.e., a data file containing an estimate of the step generator output signal. The reference waveform is produced by prior measurement by NIST of the step generator output signal (calibration step signal). When the FPOCS is in use, the calibration step signal is applied to the device under test, which is an oscilloscope sampling channel. The measured step waveform is corrected for timebase errors, then the reference waveform is deconvolved from it. The results are impulse, step, and frequency response estimates, and their associated parameters (e.g., transition duration, transition amplitude, -3 dB bandwidth) and uncertainties. The system and its components are described, and preliminary test results are presented.

PMU Interoperability, Steady-State and Dynamic Performance Tests

To ensure the performance of a synchronized phasor measurement system (SPMS) to be deployed for the Brazilian interconnected national transmission network compliant to the specific SPMS requirements, Operador Nacional do Sistema Elétrico (ONS) of Brazil has completed a phasor measurement unit (PMU) certification test as the first step of its PMU certification process for the SPMS. PMUs from eight vendors were selected and tested in this project according to a comprehensive test program specifically developed for this certification project, which is based primarily on the IEEE C37.118-2005 standard as well as the specific requirements of SPMS and its applications. This paper presents and discusses the general background information, the developed test program, the test unit selection and the testing processes, and the overall test results of this project.

Binary versus decade inductive voltage divider comparison and error decomposition

An automatic inductive voltage divider (IVD) characterization method that can measure linearity by comparing IVDs with different structures is suggested. Structural models are employed to decompose an error vector into components that represent each divider. Initial tests at 400 Hz show that it is possible to assign independent errors due to the binary and decade structures with a 2/spl sigma/ uncertainty of 0.05 parts per million (ppm) at the measured ratio values. >

NIST support of phasor measurements to increase reliability of the North American electric power grid

The importance of developing better tools for observing the status of the North American power grid is described. Focus is on the performance of the phase measurement units being deployed to give the raw data for this improved observability. How the availability of this information would have appeared during the August 2003 power blackout is described. IEEE is developing a standard for these units but no calibration service is available to use as a common reference to assure the interchangeability of units from different manufacturers. The program under way at NIST to develop such a calibration service and the coordination with the power industry to develop a guideline for performing these calibrations is presented. The future directions of work in this area are given

Testing phasor measurement units using IEEE 1588 precision time protocol

As the electric power grid is changing to a smarter more dynamically controlled system, there is increasing need for measurements that show the global status of the system for wide-area monitoring and control. These measurements require time synchronization across the grid. This synchronization is obtained by the use of GPS clocks. As the number of such synchronized devices increases there is a need to have an efficient, accurate, and reliable method of time distribution within power substations. The power industry is increasingly turning to the use of IEEE 1588 network Precision Time Protocol to meet this need in substation Intelligent Electronic Devices (IEDs). This paper examines this need in relation to the use of Phasor Measurement Units. This also paper describes the errors associated with this protocol and its application to the calibration of PMUs.