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by: Justine Nitzsche


Justine Nitzsche
GPA 3.82

Peter Persans

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About this Document

Peter Persans
Class Notes
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This 8 page Class Notes was uploaded by Justine Nitzsche on Monday October 19, 2015. The Class Notes belongs to PHYS 1200 at Rensselaer Polytechnic Institute taught by Peter Persans in Fall. Since its upload, it has received 10 views. For similar materials see /class/224878/phys-1200-rensselaer-polytechnic-institute in Physics 2 at Rensselaer Polytechnic Institute.


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Date Created: 10/19/15
Name Section L F PHYS1200 PHYSICS II Fall 2012 Lab 1 Electronics Equipment Meters Function generators Oscilloscopes in Physics II we will use the equipment you see today several times Because you will use electrical measurements in nearly all experimental science and engineering work both at RPI and when you make it into the Real World it makes sense to use Lab 1 of this course to introduce you to these devices and how to use them DC Power Supplies From the front of the room have one person from your table bring back a DC Power Supply as shown here and 2 black and 4 red banana cables a female banana adapter 7 alligator clips and 1 small resistor with brown bands I know you might need to ask what some of this Stu is That 5 what the TA 5 are here for This power supply provides a steady direct current DC at a constant voltage The display gives the approximate voltage and current being supplied between the and the outputs The rightmost output L is the ground A ground assures that your common voltage is zero relative to the earth Which is why they call it quotgroundquot The power grid that r w my 7 m m w provides electricity to your house and the outlet in front of you has a ground socket which is zero volts relative to the earth Usually the negative and ground of a power supply are not connected That means the low voltage side of your circuit may not necessarily be zero elative to earth If you need it to be you simply take an extra banana cable and connect it between the black negative output and the ground The Voltage and Current dials in the Adjust box allow you to set the maximum supplied voltage and the maximum supplied current The two lights labeled CV and CC indicate whether the power being supplied is limited by the current knob or the voltage knob DR i at D 57 xi 2 52 a U agr What is the purpose of the ground connection i 9 ErEP fMCE IE ELM 77 TU 37 77 Setting and measuring the power supply output Find the Voltage Adjust and Current Adjust knobs on your supply and turn both knobs fully counterclockwise to zero Turn on the power supply The LED should read zero for both current and voltage Turn the Current Adjust knob fully clockwise several turns Slowly rotate the Voltage Adjust knob clockwise Note what happens to the voltage meter and the current meter See that you are increasing voltage but current remains at zero Why is that You turned fully turned up the current didn t you Explain below 2 2 me n iquot Rec l 5 F 135 ewa w aw ti C1 t FN Iii 0w i N I1 Camry w a 003 at m0 C 1 rec u 7 With the current turned all the way up set the voltage at 10 volts Connect banana cables to the red 1 and the black outputs Add two alligator clips to the ends Brie y touch the clips while watching the current and voltage displays What just happened What did you just do Describe and explain below UGL DXE E b Ru PP D39 To A lt3 OSU Charmw 2 MS a m m 3 M a a i N wu Haw taxi to 7 426343 a 3 e0 lai a k rec x xi Without the alligator clips touching record the voltage and current Voltage l Current Name Section Now attach the small resistor with stripes between the alligator clips Record the voltage and the current Voltage l O a Current 39 l 3 Notice which numbers have changed and which remained the same Explain wh this is VOLT149 RELD CUNES39DAN T LU N Uquot C Q TED C ee Kn New c the tinctudf S 2 S T 61le 8 K5 LPN U 95 8 we 9386 NR What does the button labeled CC allow you to do QT A M 7 W tD l C WHY it 39 CV The battery in your car will deliver over 500 Amps if you Short the terminals39 U 39 l G 4 pl a When you touched the bare alligator clips you didn t see 500 Amps Why is that w 2 2 Elkt Ltm TED The Multimeter From the front of the room have one person bring back to your table 1 yellow multimeter A typical digital multimeter allows you to measure voltage current resistance and often things like capacitance continuity or diodes You turn it on by rotating the dial to the measurement type you want to make If it goes to sleep to save power after a few minutes just turn it off and then on again Voltage and current are measured using volts and amps The I7 or Z with a straight bar on top selects constant DC measurement The I7 or 21 with over it give you alternating current AC measurement AC displays the root mean square value of a sinusoidal voltage Vrms Vmaximum 2 More on this later in the course Notice the three plugs at the bottom The black one called COM is always used so it is called the common You use the plug on the right for voltage resistance capacitance etc for all measurements EXCEPT for current where you use the one on the left and the common Why is that A Voltmeter measures between two points It s designed so almost no current flows through it and you hook it up parallel to the circuit Ari Ammeter measures current owing in a circuit and to do that you place it in series with the circuit so thatALL of the current flows through the meter Power up the DC Power Supply and set the output for 300 volts It will help if you always use the black cable for low voltage or common parts of the circuit and the red for higher voltage parts You can trace the ow of current through a complicated circuit easier if you use black and red in a smart way Connect one red banana cable and one black cable to the appropriate plugs to measure voltage and insert the other ends into the DC Power Supply If the Power Supply says 300 volts adjust your multimeter to that it reads 300 volts What is the symbol on the multimeter that you selected 7 N39 U What is the highest voltage your Power Supply is capable of producing v What is the lowest voltage your Power Supply can provide quotxquot 00 l v39 Name Section Remove the banana cables om the Power Supply and place alligator clips on the ends Now touch the ends together and record the resistance What value for resistance do you nd 0 51 dold one bare end with one hand and the other with your other hand What s the resistance 39L I 51 1 This is the DC resistance of your body Cool huh Compare your resistance to your neighbor s resistance Why is it important for you to not touch the bare ends of a probe when taking resistance measurements C5qu M FLKJ We A vet1E1le URENEMT SSPK KLLxI as HR HE RSSmki QLALMLHTX A function generator supplies a periodic timevarying voltage of the amplitude and frequency you choose We use several different brands of function generator yours should be one of the three shown in the photos here From the ont of the room bring back a function generator black coaXial cable and two couplers and a small speaker I39l ll 39 L f 3 Look at the control panel All have a display showing the Ll LHJL e frequency in Hertz Hz cycles per second a way to vary the equency output and the amplitude Like most instruments they can do a lot 39 more than we will use in Physics II so we will be using only basic capabilities The knobs you will use most often are the FREQUENCY selector RANGE and AMPLITUDE or OUTPUT which is like volume control We also use the FUNCTION selector occasionally for sine square or triangle waves The coax output used here will be the MAIN or the one that just says OUTPUT If you are looking at a 100 HZ signal and want to quickly raise it to a 1000 Hz signal which knob or button would be the most effective one to change 2 A N 9 Equot Setting up the function generator Turn on the Function Generator Turn the amplitude knob to about the middle value Set the frequency range obtain an output of 440 Hz Do you recognize 440 Hz Make sure you are producing a Sine wave Connect a coaX cable to the output of the function generator and on the end of the coaX a coaxialtobanana converter or coupler The one that ts on the coax end is a female coupler Then two banana cables and alligator clips Now connect the alligator clips to a speaker Vary the frequency and amplitude Try different functions to see how they sound Have fun Disconnect the speaker and connect a sine wave output of the Function Generator to the multimeter Get a measurement of the VOLTAGE produced There is a right way and a wrong way If you aren t certain ask someone to veri that you have set the multimeter correctly I N Moi TS 1fhe voltage produced from a sine wave and amplitude about half way up is N Show me the symbol on the multimeter that you have it set to for this measurement Name Section Why are you not using the same voltage setting that you did for the DC Power Supply What s the difference between these two N K7 DC UUMMGE V FUR AC urnme g FC WC W N B39e39wa em ih M quot34 SIMS Nave wm 1445 4M 1111 QMA39WMe UVL MbE Turn the Amplitude knob to get an output of 30 V AC 5 What is the maximum amplitude the function generator can produce N 7 L j 7n 7 What is the minimum amplitude the function generator can produce Without turning it of k a C y l Reset the output for 30 volts AC g Change the function to a square wave What is the voltage reading on the multimeter quot L l Change the function to a triangle wave What is the voltage reading on the multimeter 2 Are these three numbers different Why do you think that may be SQqu e wade S quotVWS WT mwx M uwx L6 No 6 Q U A t TIZWJ39bL39E m MWNM wt Lamp S 9 6N m u an MereK v c Nag a mp or Me garnet The Oscilloscope up m um v a 2 I i 39 5 Now go get an oscilloscope Your room will have one of the types 3 u g 9 V w shown here Plug in your osc1lloscope and turn it on It W111 take a 1 Ah I An oscilloscope is used for observing voltage signals as a function of time Basically an oscilloscope is really just a very sensitive voltmeter using a twodimensional screen as a display The vertical axis on the screen corresponds to voltage while the horizontal axis corresponds to the time Most oscilloscopes can display two separate input channels at once but they must be on the same time scale P i few seconds to warm up 1 39 l I e l Oscilloscopes are useful to measure the frequency of a signal its amplitude or how these things change in time Setting up the oscilloscope usually involves the selection of appropriate voltage and time scales and the conditions that the display will trigger or start on This is done through the Trigger Menu where you select vhich signal Channel 1 or 2 and what conditions will act as the trigger Typical trigger conditions include the magnitude of the voltage and the direction of the change in the voltage You might for instance select to start the display when the voltage reaches 10 V and is increasing Yeah it s complicated So try this stuff Name Section Real Measurements with the Oscilloscope lave your Function Generator set to provide a 30 V AC sine wave at about 440 Hz Use a coaxial cable to connect the output of the Function Generator to the Channel 1 input of the oscilloscope Set the Channel 1 vertical scale to 2 Volts per division using the Voltsdiv knob Set the horizontal time scale by turning the TimeDiv knob to about 1 millisecond per division Hit the Trigger Menu button and where it says on the displaymenu set the trigger source to Channel 1 input Set the trigger Mode to auto Set the trigger Slope to positive or rising Adjust the trigger level using the Level knob so that the signal triggers when the signal is near zero volts Make sure the Coupling is set to DC And check to see if the Probe is set to 1X Often you ll nd it something bigger This is for magnification If you see nothing hit the runstop or run button to let it run All of these adjustments should produce a steady sinusoidal wave with several oscillations on the screen This is called a trace If this still fails read the italics below Wanna know how the pro s do it On the oscilloscope panel there is a button called AUTO SET or AUTOSCALE You can usually just nail that button once and a beautiful display results This works 95 of the time and makes a mess that you have to x by hand the other 5 Notice that you can move the trace around by using the horizontal and vertical position knobs Center your trace so it is symmetric about the horizontal axis symmetric in the vertical direction On your oscilloscope screen knowing how many volts per division determine the voltage difference between quotbe top of the sinusoidal curve and the bottom of the curve by counting squares or divisions This is called the peak to pea or pp voltage The amplitude is one half of the peak to peak voltage What is the peaktopeak voltage of your signal 8 SETS What is the amplitude Li UULTS With the function generator set to as close to 300 volts as the oscilloscope can determine unplug the cable from the oscilloscope and connect it to the yellow multimeter Measure the voltage using the multimeter What do you get v I v How does this compare to the voltage amplitude which you measured with the oscilloscope Are they the same Should they be the same If they are different why do think this is so Which do you is more accurate In um merge iiie A or Less 6 ennui e quot v cs 0 65 at 615 meet Severe Valve ML GSCAKLLIS COP CW mentee cHANEFJ w WW ClNIi f Twice per gotta On our osc1llosco e screen measure the eriod of our s1 a1 Period is the time it takes for a signal to repeat ttsel Look or a 9 pattern and measure the time for one pattern to reappear What you see should be a sine wave of some sort Sine and cosine you know repeats themselves every 360 degrees or 27 radians a The period is measured to be F I l The frequency is just the inverse of period What frequency do you measure g Compare this to what the function generator says Are they the same If not which would you believe 3 h JULD M C CCUQ B 67 Mu L L o 3 C opt to 772 371 M Crier Name Section Circuit Measurements Send someone to the front of the room to bring back to your table 3 big brown resistors no stripes and one of the smaller striped resistors Have your DC power supply set to 10 volts and the current knob turned as far clockwise as it will go Connect banana cables with alligator clips to the DC power supply and outputs 1 Take the three big brown resistors and using the other two red cables and alligator clips connect the resistors so they are all in a row called in series Now using the alligator clips on the banana cables hook the ends of the resistor chain to the power supply You are powering these three resistors in series with 10 volts DC Take the multimeter with banana cables and alligator clips and measure the voltage across the middle resistor placing your meter s alligators on either side of the middle resistor What value do you measure 36 5 f If you are not certain how to setup the multimeter ask someone 1 Measure across one of the end resistors 3 i V 3 VI Measure across the other end resistor 039 Measure the voltage across any two of the resistors Q 6 M WIN Measure across all three resistors Fill in the table below I end Resistor other end Resistor Middle Resistor any two Resistor s all three Resistor s Av 33 33 313 we 0 From this what could you conclude about the three resistors if you had no prior knowledge about them a anrsrdZ W 562 2 Take the small striped resistor Using the power supply at 10 volts as above and the multimeter set up a circuit to measure the current which passes through the smaller striped resistor Unless you are certain how to do this have someone cheek to make sure everything is setup correctly What current do you measure l Q A Is this the same reading as on the power supply I 5 AC Measurements Take two of the big brown resistors and have them wired in series as above Attach the ends of the resistor pair to the function generator You can gure out how to do this Take a co ax cable and place it on the Channel 1 input of the oscilloscope with a red and black banana coupler and banana cables on the end With alligator clips on the ends of those banana cables place the black one on Name Section the end of the resistor chain which has the black cable from the function generator THIS IS IMPORTANT What you just did is give both the oscilloscope and mction generator a common ground That s very important in circuit building and measurement lace the red cable clip on the end of the resistor chain next to the other red cable across both resistors You should see a sine wave on the oscilloscope Adjust the amplitude until you have 4 volts amplitude 8 volts peaktopeak as measured counting boxes on the screen It helps to set the voltage scale to 1 voltdiv and center the trace What is the amplitude of the signal when you are measuring across both resistors Didii 5 Amplitude is zero topeak voltage not peaktopeak Leaving the black clip Where it is move the red clip from the oscilloscope to between the resistors What is the amplitude at this point 9x WGLTS With these two amplitude measurements what can you conclude about the two resistors from this AC measurement CL W VECle Q 0f 3 STAKECK You guys are all really smart otherwise you would not have gotten into RPI So here s an interesting experiment which stumped me the first time I saw it Have the two brown resistors wired in series as you did above Power them with the function generator that you set to 4 volt amplitude as above Take your yellow multimeter Set it to AC volts and measure the voltage across just one resistor What do you get r quotf L V Measure across the other resistor What voltage reading do you get i L of Are these the same values or different Now referring to the measurements you took with the oscilloscope at the top of this page or just do it again What was the voltage amplitude you got across the one resistor R S o LTS OI our black oscilloscope wire should be next to the black wire from the function generator Now remove both the red AND the black oscilloscope wires Place them across the other resistor on the far end What voltage amplitude do you get Li U QrLTS Go back to the rst resistor next to the black function generator wire Place your oscilloscope wires across only that resistor and verify the voltage amplitude that do you get 2 J t UPS Are these two voltage amplitudes the same or different D l VQQ39 J I g So if you did this right why are you getting two different results Why does the multimeter give you one set of results and the oscilloscope the way you used it give another This is subtle but shows why you need to be care il 67quot WhitWide 71 atten tsuucttrepg MM yew QMij TelE COM th oumg iwg gcr 613T ew 61W WlSTZ QSr 5 Vt fo WM Gtwa gag jNeg a Name Section Finally here s a little preview of why you sometimes use DC Power and sometimes AC Power First most everyone knows what comes out of the wall in our homes and buildings is alternating current or AC voltage 120 volts But what comes out of a battery is DC or direct current Do you know why we use AC for houses and general electricity needs instead of DC C Ck quotJ 35 S m a UP quot U4 UWLMG 17 Fwd m i Mum AL ma MSMISX w w SEQ3 AC WM amp 5390 576 70 WWamp Me a C Ir La 6 Connect two of the brown resistors in series with the function generator attached to the ends of the chain Connect the oscilloscope across one of the resistors black of the oscilloscope to black on the function generator You should see a sine wave on the screen Take ve measurements of the voltage amplitude at the frequencies in the table below Record your results there Have someone bring back from the front of the room a small black box These are capacitors Now remove the other resistor and replace it with a capacitor plug the red banana cables without alligator clips into the white and black plugs marked A Record the voltage amplitudes in the table across the same resistor this time with that capacitor in series Voltage I 100 Hz 300 Hz SOOHZ 700Hz 9OOHz 1 100Hz Resistor only Qx A a a With capacitor 3 g 3 Jo 3 a g 3 5 Compare the voltage amplitudes with the resistor only to the amplitudes with the capacitor What do you notice How are they different with respect to frequency changes R msmrzx N0 Fmrwwc r gwkaoqwg 673qcirw 2a quotQ39rrewda39n cw 7 4w FRQeyiErxrcief This give you a small suggestion of why we sometimes want to use AC voltage and sometimes DC voltage Please return ALL to the front and leave everything neatly stacked the way you found it


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