Alternating Current and Oscilloscope - Lab Report Example

Running head: Alternating Current and Oscilloscope (CRO) Student’s name Institution Course Professor Date of Experiment Date of Submission Abstract This laboratory report discussed the Alternative current (AC) and the oscilloscope. The aims of the experiment were to be familiar with the cathode ray oscilloscope (CRO) and function generator and their usage. For instance, the use of a function generator to produce sinusoidal waveforms of various frequencies and amplitudes, the use of an oscilloscope to measure the period/frequency and amplitude of the sinusoidal waveforms and finally the use of a digital multimeter (DMM) to measure AC voltage. Among the equipment required during the experiment were; the Function Generator, Digital Multimeter (DMM) and Oscilloscope (CRO). The DMM measures the effective or root-mean-square value of the voltage. The Function Generator was set up to a produce a sine wave of frequency approximately 1 kHz while the amplitude control was set at its mid position and the horizontal control of the CRO set to 0-2ms per division. The period and the amplitude of the waveform were measured in the CRO screen. The measured and calculated period of oscillation were compared and also the DMM reading and the amplitude of the oscillation were too compared. Table of Contents Abstract 2 1.0Introduction 4 1.1Theory 4 2.0Methodology 6 2.1Procedures 6 2.1.1Task 1 6 2.1.2Task 2 7 3.0Results and calculations 7 3.1Table one 7 3.2Table two 8 4.0Discussion and conclusion 9 5.0References 10 1.0Introduction This report of the lab experiment guides the student to understand the operation of cathode ray oscilloscope (CRO). The students are able to become familiar with its usage. A calibrated CRO with the help of function generator enables one to measure amplitude, time period and frequency of the time-varying signals. Indeed, it provides a visual presentation of any waveform applied to the input terminal. The aims of the experiment were to familiarize with the following; the use of a function generator to produce sinusoidal waveforms of various frequencies and amplitudes; the use of an oscilloscope to measure the period/frequency and amplitude of sinusoidal waveforms; the use of a digital multimeter for measuring Alternative Current (AC) voltage. 1.1Theory Cathode ray oscilloscope (CRO) generally consists of a vacuum tube. The tube contains a cathode, anode, X and Y plates, anode, grid and a fluorescent screen. It works on the principle of the deflection of an electron beam by an electric field. Fig1 show a basic structure of Cathode ray oscilloscope (CRO) Consequently, the major subsystems of CRO include; cathode-ray-tube (CRT), Vertical and horizontal amplifier, sweep generator, trigger circuit and associated power supply. The equipment measures quantities for instance frequency, peak voltage, phase difference, pulse width, delay time, rise time and fall time. When the cathode is heated through application of a small potential difference across its terminals, electrons are emitted. Due to potential difference existing between the electrodes, emitted electrons are accelerated towards the anode thus forming an electron beam. The grid situated between the electrodes controls the amount of electrons passing through it. The X and Y plates are used to deflect the electron beam horizontally and vertically respectively. The X-plates of the CRO are connected to time-base circuit. The circuit applies a saw tooth voltage to the X-plates. When the sweep generator is connected to the Y-plates, it will move the bright spot horizontally across the screen. The voltage increases uniformly to a peak (sweep) and the drops suddenly (flyback). The combined sweep together with Y-voltages will give a graph that will show the variation of voltage with time. The tube sensitivity and deflecting voltages are expressed as deflection factor and deflection sensitivity. An A.C signal of sinusoidal form is the natural output of the rotary electricity generators. Fig.2 A sinusoidal wave form Where is the maximum output voltage value, and ∅ is the phase shift The root-mean-square value, vrms of the signal is given by Voltage peak-to-peak value is given by; V p-p = Number of vertical division * Volt/div Vrms value can be calculated by the formular, The Period, T is given by T= Number of horizontal Division * Time/Div Frequency, f=1/Ta 2.0Methodology The equipments required in the experiment were; Function Generator, Digital Multimeter (DMM) and the Oscilloscope (CRO). 2.1Procedures 2.1.1Task 1 1) The Function Generator was set up to produce a sine wave of frequency approximately 1 kHz 2) The amplitude control was set to its mid position and the output was connected to the channel 1 input of the CRO. The horizontal control of the CRO was set to 0.2 ms per division. 3) Then the vertical control of the CRO was adjusted so that the displayed waveform occupies most of the CRO screen 4) From then CRO screen the period and amplitude of the waveform was measured and also the DMM was used to measure the voltage output from the Function Generator. 2.1.2Task 2 In the exercise two, 1) The output frequency of the Function Generator was adjusted to be 400 kHz. 2) The controls on the oscilloscope was changed such that 1 or 2 cycles are shown on the screen i.e the timebase was set to be 0.5μs/cm 3) The voltage on the DMM was checked while the period and amplitude on the CRO were too checked. Their values were noted down. Care was observed when the variable voltage output from the Function Generator was set at zero and its power was switched off when connecting up circuits. 3.0Results and calculations 3.1Table one Frequency (Hz) Voltage readings (V) Wavelength Time Div (s) DMM CRO 10 2.69 3.2 5 20ms 20 2.6 3.2 2.5 20ms 50 2.6 3.2 4 5ms 100 2.61 3.2 2 5ms 200 2.6 3.2 2.5 2ms 500 2.57 3.2 2 1ms 1000 2.52 3.2 2.5 0.5ms 2000 2.43 3.2 2 0.2ms 5000 2.24 3.2 2 0.1ms 10000 2.16 3.2 5 20µs 20000 2.52 3.2 2.5 20µs 50000 3.31 3.2 2 10µs 100000 1.34 3.2 2 5µs 200000 0.06 3.2 2.5 2µs 500000 0.00 3.2 2 1µs 3.2Table two CRO DMM CRO f (Hz) Divs Vertical control Vpkpk Vpk Vrms Vms Time divisions Divs Periods (s) f (Hz) 10 5 3.2 2.69 20ms 5 0.1 10 20 2.5 3.2 2.6 20ms 2.5 0.05 20 50 4 3.2 2.6 5ms 4 0.02 50 100 2 3.2 2.61 5ms 2 0.01 100 200 2.5 3.2 2.6 2ms 2.5 0.005 200 500 2 3.2 2.57 1µs 2 0.002 500 1000 2 3.2 2.52 0.5ms 2 0.001 1000 2000 2.5 3.2 2.43 0.2ms 2.5 0.0005 2000 5000 2 3.2 2.24 0.1ms 2 0.0002 5000 10000 5 3.2 2.16 20µs 5 0.0001 10000 20000 2.5 3.2 2.52 20µs 2.5 0.00005 20000 50000 2 3.2 3.31 10µs 2 0.00002 50000 100000 2 3.2 1.34 5µs 2 0.00001 100000 200000 2.5 3.2 0.06 2µs 2.5 0.000005 200000 500000 2 3.2 0.00 1µs 2 0.000002 500000 In task one The values of Period = Amplitude = Root-mean-square value of voltage measured by DMM =2.51V But then V0= 2.51*√2 3.55V In task two Output frequency of the function generator = 400 kHz Voltage on the DMM = Period =10 Amplitude on the CRO =3.6 4.0Discussion and conclusion 5.0References A. C. Melissinos & J. Napolitano.”Experiments in Modern Physics”, San Diego, CA: Academic Press, 2003 Cheruku,” Electronic Devices And Circuits, 2/E.”Pearson Education India, 2008 Russel L. Meade, Robert Differenderfer,”Foundations of Electronics: Circuits and Devices’, Thomson Delmar Learning, 2003. Read More