Download AC Measurements in Circuit Analysis II - Georgia Southern University - Prof. Maria Alba-Fl and more Lab Reports Electrical Circuit Analysis in PDF only on Docsity! Circuit Analysis II TEET 3145 Laboratory # 1 AC Measurements Fall 2009 Georgia Southern University Mechanical and Electrical Engineering Technology Page 1 of 4 NAME:____________________________ Introduction. Alternating current (AC) circuits have sources that change in value with time. The most common AC source is a sine wave generator. Two common ways to describe a sine wave voltage are: 1. Peak -to- peak value. The oscilloscope can be used and the distance from the top of the wave to the bottom will be the peak-to-peak value of the signal. 2. RMS (root means square) value. A digital multimeter (DMM) can be use to obtain the RMS value of an AC signal A digital multimeter measures the AC voltage as if it were a DC voltage. The multimeter answers the question: “What DC voltage would cause the same effect (power dissipation in a resistor) as the AC voltage being measured?” This value is called the effective voltage or RMS value. Mathematically the RMS value can be calculated by squaring the voltage, finding the average (mean), then taking the square root. The more expensive multimeters will read the correct rms value of any voltage waveform. These are sold as “true” rms. Lower end meters are only calibrated to read the rms value of a sinusoidal waveform. Procedure. 1. Build the series circuit shown in Figure 1. For the AC signal set the function generator to 1.0 Vp-p at 500 Hz as measured with the oscilloscope (peak-to-peak values). 2. Using the oscilloscope, measure the voltage at points a, b, and c (all with reference to ground). Sketch the observed signals and record their values in the horizontal and vertical axis, include the units for both axis. (see the oscilloscope draw at the end of this handout). 3. Calculate the voltages across each resistor, R1, R2 and R3 using the oscilloscope measurements in step 2. Fill out Table 1. 4. Using the DMM, measure the voltage at points a, b, and c (all with reference to ground). Record their values in Table 2. 5. Using the DMM measure the voltages across R1 and R2, this is, VR1 =Vab and VR2= Vbc . Record the values in Table 2. Figure 1 Circuit for the experiment Circuit Analysis II TEET 3145 Laboratory # 1 AC Measurements Fall 2009 Georgia Southern University Mechanical and Electrical Engineering Technology Page 2 of 4 Measured voltages (peak-to-peak) Calculated voltages (peak-to-peak) Va and GND Vb and GND Vc and GND V R1 VR2 VR3 Table 1. Peak-to-peak values Measured voltages (RMS) Measured voltages (RMS) Va and GND Vb and GND Vc and GND VR1 VR2 VR3 Table 2. RMS values Questions: 6. Address the following questions in your report. a) Why can you measure VR1 =Vab and VR2= Vbc with the DMM directly, but not with the oscilloscope directly ? b) Calculate the ratios of the peak-to-peak voltage measurements and the multimeter RMS measurements. Is there a consistent proportion between them ? Instructor’s Initials: _________ The instructor’s initials note that the student recorded measurements appropriate to the current laboratory. The initials do not certify that all required measurements are correct or complete. The instructor’s initials are only made after the laboratory workbench is cleaned off and all laboratory equipment and components are returned to their appropriate location.
