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Unformatted text preview: Tufts University School of Engineering Department of Electrical and Computer Engineering ES3 - Introduction to Electrical Circuits Fall 2007 Lab Section: Friday 2:30-4:30pm Experiment 2 Measurement of Time-Varying Signals Name: Teddy Portney Edward . Portney@ tufts . edu Submitted to: Bertan Hallacoglu Experiment Performed: October 12, 2007 Experiment Due: October 19, 2007 I. PURPOSE The purpose of this lab was to use an oscilloscope to examine the behaviors of different electrical components, as well as a standard alternating current, as supplied by a function generator . Using these two extremely useful laboratory tools, the capacitor relationship, i(t) = C dv/dt was verified . This lab also showed that it is possible to calculate an unknown capacitance with these two simple, common laboratory tools, as well as a common resistor . An LCR meter was also used to determine the inductance and resistance of a voice coil in a speaker . This lab also introduced the concept of electrical impedance and its effect on the performance of a speaker . II. INTRODUCTION This lab dealt primarily with learning how to use common laboratory instruments, specifically the oscilloscope and the function generator . The function generator is a tool used to accurately produce an alternating current . This machine has many different knobs that allow the user to accurately change all variables in the equation for the voltage of a wave . It allows for the production of square waves, saw blade waves, and sine waves . It is also capable of accurately setting a frequency, and allows for amplitude and offset adjustments . Similarly, the oscilloscope is a tool used to measure extremely rapidly changing voltages . The oscilloscope has a large monitor, onto which it projects an image of a voltage . For all parts of this lab, we used the function generator to produce sine waves, the simplest of the three waveforms mentioned above . The image shown on the oscilloscope when a circuit was set up correctly was a nearly perfect sine wave . This wave was nearly perfect, as opposed to perfect, because there were other electronic devices in the laboratory room, all emitting electronic noise, which is picked up by the oscilloscope . This explains why the signal shown on the oscilloscope, when there was nothing plugged into either input, was not constant at zero . The major identity used in this lab was the equation i = C dv/dt, or current flowing through a capacitor is equal to the capacitance multiplied by the derivative of the voltage flowing through the capacitor . Another useful equation in this lab was the equation for a resultant voltage sine wave, produced by the function generator . This equation is given as v(t) = A sin(2 f t) volts, where A is the amplitude of the sine wave, f is the frequency in Hertz, and t is the time ....
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