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ROCHESTER PHY 103 - Lab 1 - Measurements of Frequency

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Physics of Music PHY103 Lab ManualLab 1 – Measurements of FrequencyEQUIPMENT and PREPARATIONINTRODUCTIONPURPOSEPROCEDUREDATA ANALYSIS (Lab Report)Physics of Music PHY103 Lab ManualLab 1 – Measurements of FrequencyEQUIPMENT and PREPARATIONPart A:- Oscilloscopes (get 5 from teaching lab)- BK Precision function generators (get 5 from Thang or teaching lab)- Counter/timers (PASCO, 4 + 1 other)- Connectors and cables (BNC to BNC’s, banana plug pairs) connecting function/signal generators to oscilloscopes and speaker.- BNC to 2 leads- Adaptors: mike to BNC so that output of preamps can be looked at on oscilloscope.- BNC to banana adapters- BNC T- adapters- Oscilloscope probes- Pasco open speakers- Microphones, preamps, mic stands- Strobes (3) optionalWarning: do not place speakers near oscilloscope screens as they can damage the CRT (cathode ray tube) screens.Note: The professor will attempt to have the equipment out and available for the labs. However the TAs/TIs should check that the equipment is ready to use, that every lab setup has all the necessary equipment. The TA/TIs should also be familiar with the lab and know how to troubleshoot the equipment.INTRODUCTIONIn this lab, we will be measuring the frequency of a signal using three different methods. The firstmethod involves the use of the function generator. A function generator is an instrument that can producesine, square, and triangular waves at a given frequency. The second method makes use of the oscilloscope.An oscilloscope is an instrument principally used to display signals as a function of time. The final methodfor measuring the frequency uses the counter/timer. A counter/timer is an instrument that can give a veryaccurate measurement of the frequency of a signal by counting each time a voltage crosses a particularvalue. The frequency, f, and period, T, of a wave are related in the following way:(Equation 1)For frequency in Hz (cycles per second), the period is given in seconds. This equation makessense because the frequency is the number of cycles that fits into 1 second (fT=1).The electrical signals created by a function generator can become “sound waves” when passedthrough a speaker. In this lab we will verify this by looking at the signal output from the microphone onthe oscilloscope. To send signals between the various instruments we will use wires/cables with thefollowing connectors:Physics of Music PHY103 Lab ManualBNC connector (male)For shielded cableBanana Plug (male)¼’’ phone (TRS) connector(male)PURPOSEThe purpose of this lab is to gain familiarity with varying electronic signals and connect detection of sound waves to the equipment that we use to measure them. We will gain a working knowledge of a function generator, an oscilloscope, and a counter/timer. We will look at signals picked up by an oscilloscope probe and that from a microphone. We will experiment with different ways of measuring frequency. The goal of the lab report is to compare and contrast our different measuring frequency measuring techniques.PROCEDUREPart I – The Function Generator- Turn on the function generator.- Press in the button on the front panel with the sine wave picture.- Where it is labeled “Range,” press the “500” button.- Use the “Course” and “Fine” tuning dials (where it is labeled “Frequency” on the front panel) untilthe display reads 300 Hz.- In your notebook, write “300 Hz” for the value you obtained for your frequency using the functiongenerator on your first trial. You will want to record your different measurements!- Turn the Output level (amplitude) knob on the function generator so the output is at about half ofthe maximum (this is so it won’t make a very loud sound in the next step). - Connect the output of the function generator to the speaker. Adjust the amplitude. Vary thefrequency from the function generator. Make sure you can hear a tone from the speaker. Get afeeling for what frequencies correspond to which sounds. - Explore the range of your hearing in frequency. What is the lowest frequency you can hear andthe highest you can hear?- Change the signal to a square wave or a triangle wave. Notice that they have different sounds.- Revert to sine wave, set the frequency back to 300Hz and disconnect the speaker.Please keep the speaker away from the oscilloscope to prevent damage to the CRTscreens!Part II – The Oscilloscope (you will be using Tenma scopes)1. Turn on the oscilloscope by pushing in the power. It will take a few seconds for a trace to appearon the screen. If one does not appear in a few seconds, try increasing the trace intensity (see #3).2. Connect the output of the function generator to one of the inputs of the oscilloscope. 3. Adjust the intensity. This is done by turning the intensity button on the Tenma scopes in theDisplay section.4. There is a FOCUS knob. You can adjust this knob to focus the line in the CRT monitor.Physics of Music PHY103 Lab Manual5. Note that if the speaker is near the oscilloscope, its magnet can distort the display. This is kind offun to show but if you do too much of this it can damage the CRT and permanently warp it (wehad this happen one year.)6. There is a MODE switch in the “Vertical” section. If your signal from the function generator isgoing into Channel 1 then move this switch to “CH 1.” This allows you to look at channel 1.There are two channels available so that it is possible to compare two traces at once. To showboth traces at once (that is the signals going into channel 1 and 2), select the DUAL mode.Ordinarily you look channel 1 or 2 in the y axis vs time in the x axis.. The X-Y mode allows youto look at an x versus y display. The horizontal (x-axis) signal is connected through the CH1 Xinput connector and the vertical (y-axis) signal is connected through the CH2 Y input connector.The ADD mode allows two traces to be added together. If your signal is going into Channel 2then you would make sure that the MODE switch is either on “CH2” or on “Dual”.7. There is a SOURCE switch in the “Trigger” section. Make sure this switch is on “CH1.” (if yoursignal from the function generator is in Channel 1) or on “CH2” (if your signal is going inChannel 2). 8. Using the CH1 Y shift control (the vertical arrows) in the “Vertical” section to make sure that thetrace is in the middle of the screen vertically.9. Using


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