EXPERIMENT III RESONANCE IN RLC CIRCUITS
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EXPERIMENT III RESONANCE IN RLC CIRCUITS Venue: Instrumentation and Measurement Laboratory in E2 I. INTRODUCTION This laboratory is about studying resonance in RLC series and parallel circuits. This experiment will be used to examine the sinusoidal frequency response of the series and parallel to see at what frequency the current through an RLC series becomes or the voltage across a parallel RLC circuit reaches maximum value. A network is in resonance when the voltage and current at the network input terminals are in phase and the input impedance of the network is purely resistive. II. PRE-LAB Do the ORCAD simulations of both RLC parallel and RLC series circuits. III. EXPERIMENTAL METHOD, MEASUREMENT AND READINGS Consider the Parallel RLC circuit of figure 1. The steady-state admittance offered by the circuit is: Y = 1/R + j( ωC – 1/ωL) Resonance occurs when the voltage and current at the input terminals are in phase. This corresponds to a purely real admittance, so that the necessary condition is given by ωC – 1/ωL = 0 ECE Lab III ECE 2201 SEMESTER I, 2007/2008 By Sheroz Khan The resonant condition may be achieved by adjusting L, C, or ω. Keeping L and C constant, the resonant frequency ωo is given by: Equipment Required: Square-wave generator, discrete circuit components of R=1 KΩ, L= 27mH and C=1uF, oscilloscope and square-wave generator. Set up the RLC circuit as shown in Figure 1 Figure 1 Apply a 4.0 V (peak-to-peak) sinusoidal wave as input voltage to the circuit. Set the Source on Channel A of the oscilloscope, and the voltage across the ca[pcitance on Channel B of the oscilloscope. Vary the frequency of the sine-wave on signal generator from 500Hz to 2 KHz in small steps, until at a certain frequency the output of the circuit on Channel B, is maximum. This gives the resonant frequency of the circuit. ECE Lab III ECE 2201 SEMESTER I, 2007/2008 By Sheroz Khan DATA TABLE – I PARALLEL RESONANCE f 500 Hz 600 Hz 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 C 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF R 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω L 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH Vo V(t) reading Repeat the experiment using for the series resonant circuitry in Figure 2, and use L = 33mH and C = 0.01uF and R = 1 KΩ. The Vo voltage on the resistor is proportional to the series RLC circuit current. Figure 2 ECE Lab III ECE 2201 SEMESTER I, 2007/2008 By Sheroz Khan DATA TABLE – Ii SERIES RESONANCE f 500 Hz 600 Hz 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 IV. C 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF 0.01uF R 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω 1000 Ω L 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH 33mH Vo V(t) reading CONCLUSIONS Find the resonant frequency using equation given in the before and compare it to the experimental value in both cases. Plot the voltage response of the circuit and obtain the bandwidth from the half-power frequencies using equation. ECE Lab III ECE 2201 SEMESTER I, 2007/2008 By Sheroz Khan
