Engg225_lab4.pdf - ENGG 225 Fundamentals of Electrical...

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ENGG 225 Fundamentals of Electrical Circuits and Machines Laboratory #4 Steady-State AC Circuits 1 Introduction Earlier in ENGG 225, we studied DC circuits along with some common and important circuit configurations, such as the Wheatstone bridge. We further used DC circuits to present, and demonstrate in detail, the systematic high-level methods of circuit analysis, such as the node-voltage and mesh-current methods, Th´ evenin’s theorem, and the principle of superposition. AC circuits also clearly make up an important and large class of electric circuits, and in this lab, you will apply the same circuit analysis methods to analyze them. There are many important practical applications of AC circuits, and you will explore one such application here, that of signal conditioning, simply called “filtering.” 1.1 Learning Outcomes At the end of this laboratory session, you will be able to analyze, design, and test AC circuits, and to design and experiment with practical filter circuits. Specifically, you will learn: to verify Th´ evenin’s theorem for an AC circuit; to design and build a complex voltage divider that acts as a simple lowpass filter circuit with a prescribed “cutoff frequency;” how a simple series-resonant circuit can be used to reject a sinusoidal voltage having a particular frequency; a practical application of a simple lowpass filter circuit for reducing contaminat- ing noise interference in a simulated electrocardiogram (ECG) measurement.
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ENGG 225 Lab #4 (AC Circuits) – Winter, 2018 2 1.2 UCEE Acknoweldgment The course instructors for ENGG 225 continue to greatly acknowledge the University of Calgary Engineering Endowment (UCEE) Fund for substantial funding toward the purchase of important high-quality laboratory test equipment and supplies needed to enhance the learning value of the laboratories in the course. 2 Background Review 2.1 Th´ evenin Equivalent Circuits Th´ evenin’s theorem states for DC circuits that: Any two-terminal linear DC circuit can be replaced with an equivalent circuit consisting of a DC voltage source and a series resistance. It is the same for AC circuits, except that in AC circuits, the series resistance is in general replaced by an impedance, and the DC source by an AC source. You may wish to review Th´ evenin equivalent circuits in Sections 2.6 (DC circuits) and and 5.6 (AC circuits) in the course textbook. 2.2 Frequency-Dependent Circuits – Filters Consider the simple AC circuit in Fig. 1, which consists of a sinusoidal voltage source v in ( t ) in series with a resistor and capacitor. This is nothing more than a voltage divider circuit of the type considered in Lab #2, but now with sinusoidal voltages and currents. Although this is clearly a simple circuit, it has a very useful practical application called “filtering.” + _ R v (t) out v (t) in + _ C Fig. 1. A simple lowpass filter circuit Let the frequency of the sinusoidal voltage source v in ( t ) be ω = 2 πf . The fre- quency of the sinusoidal voltages and currents throughout the circuit are all the same as v
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  • Fall '10
  • NingxuCai
  • Alternating Current, RC circuit, Electrical impedance, Thévenin's theorem, Electronics terms

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