www.Vidyarthiplus.com 10144EC602 MEASUREMENTS AND INSTRUMENTATION DEPT/ YEAR/ SEM:ECE/ III/ VI PREPARED BY: Ms. G.GEETHA/ Assistant Professor/ECE www.Vidyarthiplus.com
www.Vidyarthiplus.com SYLLABUS 10144EC602 MEASUREMENTS AND INSTRUMENTATION LTPC 3003 UNIT I BASIC MEASUREMENT CONCEPTS 9 Measurement systems – Static and dynamic characteristics – Units and standards of measurements – Error analysis – Moving coil, moving iron meters – Multimeters – True RMS meters – Bridge measurements – Maxwell ,Hay ,Schering ,Anderson and Wien bridge. UNIT II BASIC ELECTRONIC MEASUREMENTS 9 Electronic multimeters – Cathode ray oscilloscopes – Block schematic – Applications – Special oscilloscopes – Q meters – Vector meters – RF voltage and power measurements. – True RMS meters. UNIT III SIGNAL GENERATORS AND ANALYZERS 9 Function generators – pulse and square wave generators, RF signal generators – Sweep generators – Frequency synthesizer – Wave analyzer – Harmonic distortion analyzer – Spectrum analyzer - digital spectrum analyzer, Vector Network Analyzer – Digital L,C,R measurements, Digital RLC meters. UNIT IV DIGITAL INSTRUMENTS 9 Comparison of analog and digital techniques – Digital voltmeter – Multimeters – Frequency counters – Measurement of frequency and time interval – Extension of frequency range – Automation in digital instruments, Automatic polarity indication – automatic ranging, automatic zeroing, fully automatic digital instruments, Computer controlled test systems, Virtual instruments . UNIT V DATA ACQUISITION SYSTEMS AND FIBER OPTIC MEASUREMENTS 9 Elements of a digital data acquisition system – Interfacing of transducers – Multiplexing – data loggers - Computer controlled instrumentation – IEEE 488 bus – Fiber optic measurements for power and system loss – Optical time domains reflectometer. Total = 45 PERIODS TEXT BOOK 1. Helfrick, A.D. and William Cooper, D., ―Modern Electronic Instrumentation and Measurement Techniques‖, PHI, 2007. 2. Ernest O. Doebelin, ― Measurement Systems- Application and Design‖, TMH, 2007. REFERENCES 1. Carr, J.J., ―Elements of Electronics Instrumentation and Measurement‖, Pearson education, 2003. 2. David A. Bell,‖Electronic Instrumentation and measurements‖, Prentice Hall of India Pvt Ltd, 2003. 3. B.C. Nakra and K.K. Choudhry, Instrumentation, ―Measurement and Analysis, Edition‖, TMH, 2004. 4. James W. Dally, William F. Riley, Kenneth G. McConnell, Instrumentation for Engineering Measurements, 2nd Edition, John Wiley, 2003. www.Vidyarthiplus.com
www.Vidyarthiplus.com UNIT I - BASIC MEASUREMENT CONCEPTS: Measurement system: Measurement system any of the systems used in the process of associating numbers with physical quantities and phenomena. Although the concept of weights and measures today includes such factors as temperature, luminosity, pressure, and electric current, it once consisted of only four basic measurements: mass (weight), distance or length, area, and volume (liquid or grain measure). The last three are, of course, closely related. Basic to the whole idea of weights and measures are the concepts of uniformity, units, and standards. Uniformity, the essence of any system of weights and measures, requires accurate, reliable standards of mass and length . Static Characteristics of Instrument Systems: Output/Input Relationship Instrument systems are usually built up from a serial linkage of distinguishable building blocks. The actual physical assembly may not appear to be so but it can be broken down into a representative diagram of connected blocks. In the Humidity sensor it is activated by an input physical parameter and provides an output signal to the next block that processes the signal into a more appropriate state. A key generic entity is, therefore, the relationship between the input and output of the block. As was pointed out earlier, all signals have a time characteristic, so we must consider the behavior of a block in terms of both the static and dynamic states. The behavior of the static regime alone and the combined static and dynamic regime can be found through use of an appropriate mathematical model of each block. The mathematical description of system responses is easy to set up and use if the elements all act as linear systems and where addition of signals can be carried out in a linear additive manner. If nonlinearity exists in elements, then it becomes considerably more difﬁcult — perhaps even quite impractical — to provide an easy to follow mathemat- ical explanation. Fortunately, general description of instrument systems responses can be usually be adequately covered using the linear treatment. The output/input ratio of the whole cascaded chain of blocks 1, 2, 3, etc. is given as: [output/input]total = [output/input]1× [output/input]2× [output/input]3 … The output/input ratio of a block that includes both the static and dynamic characteristics is called the transfer function and is given the symbol G. The equation forG can be written as two parts multiplied together. One expresses the static behavior of the block, that is, the value it has after all transient (time varying) effects have settled to their ﬁnal state. The other part tells us how that value responds when the block is in its dynamic state. The static part is known as the transfer characteristic and is often all that is needed to be known for block description. The static and dynamic response of the cascade of blocks is simply the multiplication of all individual blocks. As each block has its own part for the static and dynamic behavior, the cascade equations can be rearranged to separate the static from the dynamic parts and then by multiplying the static set and the dynamic set we get the overall response in the static and dynamic states. This is shown by the sequence of Equations. Instruments are formed from a www.Vidyarthiplus.com connection of blocks. Each block can be represented by a conceptual and mathematical model. This example is of one type of humidity sensor.
www.Vidyarthiplus.com Drift : It is now necessary to consider a major problem of instrument performance called instrument drift . This is caused by variations taking place in the parts of the instrumentation over time. Prime sources occur as chemical structural changes and changing mechanical stresses. Drift is a complex phenomenon for which the observed effects are that the sensitivity and offset values vary. It also can alter the accuracy of the instrument differently at the various amplitudes of the signal present. Detailed description of drift is not at all easy but it is possible to work satisfactorily with simpliﬁed values that give the average of a set of observations, this usually being quoted in a www.Vidyarthiplus.com conservative manner. The ﬁrst graph (a) in Figure shows typical steady drift of a measuring