Digital Wattmeter Using a Sampling Method

Turgel, R. S.

doi:10.1109/tim.1974.4314307

Cited by 59 publications

(16 citation statements)

References 2 publications

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“…The electrodynamometer has now been replaced by a digital sampling wattmeter, an instrument concept pioneered by Turgel [1] and developed further by the National Physical Laboratory in the U.K. Power is measured by multiplying digitized samples of the current and voltage waveforms and, if the correct sampling strategy is used, relatively few samples per waveform cycle are required [2] - [4]. An inherent advantage of the method is that the digital multiplication gives complete independence between the current and voltage channels, allowing each to be calibrated separately.…”

Section: Wattmeter Configurationmentioning

confidence: 99%

Digital sampling laboratory wattmeter

Corney

Pullman

1987

IEEE Trans. Instrum. Meas.

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where Vi and I, are simultaneous samples of voltage and current equally spaced in time. It has been shown that, provided certain conditions are satisfied, (2) gives an ac- II. THE DIGITAL SAMPLING TECHNIQUEThe average power measured over an interval T is given by Abstract-A versatile laboratory multifunction wattmeter based on digital sampling has been developed for incorporation into a laboratory calibration system. The meter uses two IS-bit AID converters and achieves an overall power measurement accuracy of 0.015 percent of applied volt-amperes at mains frequencies over. the range 100 rnA to 100 A and 5-100 V. Although intended for system use through the IEEE 488 bus, the meter can be used as a stand-alone instrument if required. curate result for relatively few samples [2]. Furthermore, the samples need not be taken over a single period but can be spread over m periods (where m is an integer) allowing the sampling interval to be increased accordingly. The conditions required are: 1) the sampling must occur over an integral number of waveforms; and 2) the waveform is stationary for the duration of measurement.With these two conditions satisfied the result is accurate for all power harmonics except; those harmonics k, for which km / n is an integer. The harmonic power terms arise from harmonics V p and I q in the voltage and current waveforms combining to produce power components at the (p + q )th and (p -q )th harmonics. Therefore if m and n have no factors in common, errors are limited to those voltage-current products where p + q or p -q is an integral multiple of n, the number of samples taken.Hence, for low values of n, errors may not be negligible particularly if both waveforms are nonsinusoidal or if a dc component is present on one waveform while the other contains significant distortion. Nevertheless the technique promises high accuracy for waveforms which are essentially sinusoidal, and it is under these conditions that the power calibration standard is used. III . WATTMETER CONFIGURATIONThe basic configuration of the digital sampling wattmeter is shown in Fig. 1. The instrument is controlled by an 8085-based single-board computer which is multibus compatible. Signal conditioning boards for current and voltage are placed in a separately screened compartment to shield against the noise generated by the processor board. These boards comprise a selectable gain voltage amplifier and current-to-voltage converter for the voltage and current signals, respectively. The gains are automatically switched by the processor so that the output signal levels are as close as possible to, but do not exceed, the ± 5-V input range of the analog-to-digital converters. The digitization is performed by two IS-bit hybrid converters which are simultaneously triggered at a sampling interval previously determined by the processor. The samples from each converter are multiplied together and the products are summed and then averaged to obtain the power measurement. During data acquisition and subsequent processing, checks are mad...

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Section: Wattmeter Configurationmentioning

confidence: 99%

Digital sampling laboratory wattmeter

Corney

Pullman

1987

IEEE Trans. Instrum. Meas.

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“…The unbalance in the power network is created when one of the three phases is overloaded, while the other are relieved. This leads to the extreme flow of current through the neutral wire [20,21]. This problem adds to other problems which affects the efficient transfer of the electric power.…”

Section: Introductionmentioning

confidence: 99%

Wireless Control System for Three Phase Loads Balancing in Distribution Networks

Abdulmuttalib¹,

Fadhela²,

Osama³

2018

IJCA

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The aim of this paper is to design and construction a wireless control system for three phase loads balancing in a regional transformer. This system is designed to solve the problems of the loads imbalance to avoid the losses of the electricity in the distribution networks and also to protect the elements of the network like transformers from damages. The important parts of the wireless control system are the three phase smart energy meters which equipped at each house within this system. These meters send their electrical measurement quantities wirelessly to the main control system (base station). The base station uses the received electrical measurement quantities of the smart meters to investigate the equilibrium among the three phase lines of the transformer by swapping some phases of the houses. The swap phases are chosen according to the heuristic search algorithm and the equilibrium is achieved when the maximum acceptable rate of PUI (phasing unbalance index) is 10 %. Each smart meter in each house is equipped by six contactors used for the phases swapping. The designed wireless control system is tested in several experiment results to indicate it is performance. General TermsDistribution network, Loads balancing system.

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“…Until now, some achievements [1][2][3][4][5][6][7][8][9][10][11][12][13][14] involving in measuring AC signals have been presented. [1][2][3][4][5][6][7][8][9] have been suitably used in wattmeter and digital multimeter, etc. [10][11][12][13][14] are investigated on the topic of root-mean-square (RMS) converter.…”

Section: Introductionmentioning

confidence: 99%

A low-cost CMOS dual-mode AC/DC data converter for signal measuring technique

Chiang

Kao

Huang

2009

Analog Integr Circ Sig Process

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A low-cost CMOS dual-mode AC/DC data converter for signal measuring technique is newly proposed. Instead of traditional full wave rectification, the realized synchronous rectification circuit is more attractive due to the easier integration and lower cost. In this paper, the design strategies of implementing the signal processing of AC and DC modes in the integrated circuit are discussed completely. Proven through SIMULINK in system level and SPICE simulations in circuit level, simulation results show that the proposed dual-mode AC/DC data converter achieves 8-bit resolution in DC mode and 7-bit resolution in AC mode. Measurement results have successfully verified the correct functions and performance of the proposed data converter and confirmed it for AC/DC signal measuring technique. The area of this chip is 710 9 630 lm 2 and the measured power consumption is 5.1 mW. The proposed dual-mode AC/DC data converter is suitable for the system of analog and mixed-signal boundary scan.

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Digital Wattmeter Using a Sampling Method

Cited by 59 publications

References 2 publications

Digital sampling laboratory wattmeter

Digital sampling laboratory wattmeter

Wireless Control System for Three Phase Loads Balancing in Distribution Networks

A low-cost CMOS dual-mode AC/DC data converter for signal measuring technique

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