Deo Prabha, Vasant; Dr.Sridhar, C S(Cochin University of Science and Technology, 1980)
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Abstract:
RMS measuring device is a nonlinear device consisting of linear and
nonlinear devices. The performance of rms measurement is influenced by a number
of factors; i) signal characteristics, 2) the measurement technique used and
3) the device characteristics. RMS measurement is not simple, particularly when
the signals are complex and unknown. The problem of rms measurement on high
crest-factor signals is fully discussed and a solution to this problem is presented
in this thesis.
The problem of rms measurement is systematically analized and found
to have mainly three types of errors: (1) amplitude or waveform error 2) Frequency
error and (3) averaging error. Various rms measurement techniques are studied
and compared. On the basis of this study the rms -measurement is reclassified
three categories: (1) Wave-form-error-free measurement (2) High-frequncy-error
measurement and (3) Low-frequency error-free measurement. In modern digital
sampled-data systems the signals are complex and waveform-error-free rms
measurement is highly appreciated.
Among the three basic blocks of rms measuring device the squarer
is the most important one. A squaring technique is selected, that permits shaping
of the squarer error characteristic in such a way as to achieve waveform-errob
free rms measurement. The squarer is designed, fabricated and tested.
A hybrid rms measurement using an analog rms computing device and
digital display combines the speed of analog techniques and the resolution and
ease of measurement of digital techniques. An A/D converter is modified to perform
the square-rooting operation. A 10-V rms voltmeter using the developed rms detector
is fabricated and tested.
The chapters two, three and four analyse the problems involved in rms
measurement and present a comparative study of rms computing techniques and
devices. The fifth chapter gives the details of the developed rms detector that
permits wave-form-error free rms measurement. The sixth chapter, enumerates the
the highlights of the thesis and suggests a list of future projects
Description:
Department of Electronics, Cochin University of Science and Technology