The purpose of this lab is familiarize you with the basic functions of an oscilloscope and function generators in the analog lab.

1. (You will be guided through each step outlined here by the lab instructor)
   1. Turn on the oscilloscope with the button in the  upper right corner. Attach a BNC to alligator cable to the Channel 1 BNC input connector.
       
   2. On the oscilloscope, set the following controls:

      Channel 1 Volts / Division = 2 (The CH 1 button enables/disables the channel, turn VOLTS/DIV knob).
      Time / Division = 200us (Turn SECONDS/DIV knob).
      Trigger Source = Channel 1 (select Channel 1 from the Trigger Source menu).
       

   3. Turn on the function generator. Attach another BNC to alligator cable to the output connector (be careful not to attach it to the Sync (TTL) output). Attach the red alligator clips from both cables together. Repeat with the black clips. 
      
   4. You will now configure the function generator to output a 8Vpp (peak-to-peak), 1 Khz sinusoidal wave.

      
                 - Use the function keys to select the sinusoidal wave pattern.

                - Use frequency and range controls to set the output frequency to 1 Khz.

                - Use the amplitude control and the display on the oscilloscope to set the output
                   amplitude to 8 volts peak to peak.
       

   5. You should now see a sinusoidal wave on the oscilloscope. If not, then ask a lab assistant for help. The problem may be with some oscilloscope settings, some function generator settings, or the physcial connection.
       
   6. Now, make sure the sinusoidal wave is vertically centered on your scope. Use the channel 1 ground switch and the channel 1 vertical position control.  
       
   7. Since the cosine wave is the standard for sinusoidal wave patterns, adjust the horizontal position of the wave so that the positive peak amplitude intercepts the vertical axis. This can be  done by highlighting horizontal position with the "selector" and then adjusting the position with the variables control.

   
   You should now have a stable cosine wave with an amplitude of 4volts, a phase shift of 0 degrees, and a frequency of 1 Khz (see equation 1) displayed on the oscilloscope. Have a lab TA verify this.

   v(t) = 4 cos(2 * pi * 1000t + 0) volts          (1)
2. Using the cursors.

    The oscilloscopes are equipped with a set of horizontal and vertical cursors to aid in obtaining measurements. You can use these to measure various parameters like peak voltage, period, and frequency.
    

   1. Measure the Peak-to-Peak amplitude of the waveform using the horozontal cursors. To do this, use "selector" to highlight measure.  Then use thevariables knob to set one cursor at a minimum of the cosine wave.  Push the cursor botton down until the other cursor is seleted and use the variables knob to set this cursor to a maximum of the cosine wave.  The oscilloscope will display the voltage difference between the two cursors.
       
   2. Measure the Period of the waveform using the vertical cursors. To do this, use the selector switch to display vertical cursors.  Set the cursors to measure the period of one cycle of your waveform as you did in part "a".  The display should show the period of the cosine wave.

      
      

3. Given equation 2:

    

   v(t) = 5 cos(62832t + 0) volts            (2)

   
   

   1. What is the frequency of the waveform in hertz? What is Vp?

      
       

   2. Now, we will adjust the function generator to output the waveform in equation 2. Start bringing up the frequency from 1 Khz to the value you calculated in part a, and notice what happens to the waveform displayed on the oscilloscope. Rreadjust the sec/div knob on the scope until one or two periods take up most of the the screen.  What happens to the signal displayed on the scope as the frequency from the function generator gets higher?

      
       

   3. With the cursors, measure Vp (peak) and Vpp (peak-to-peak) and record these values in your lab book.

      
       

   4. With the cursors, measure the frequency of the waveform and record this value in your lab book.

      
       

   5. Sketch the waveform as best as you can in your lab book.

      
       

4. Build the circuit in Figure 1.

   
     

   NOTE: You do not have to use the protoboard's power supply for this circuit. The function generator is providing the voltage source.
    
    
   
   

   

   Figure 1.

   You will need another BNC to alligator connector to use for measuring on Channel 2 of the oscilloscope. Hook up the Oscilloscope's Channel 1 and the Function Generators red alligator clips together. This node is the positive voltage supply. Hook up all 3 black alligator clips together. This mode is the ground node. Essentially, Channel 1 will be measuring Vs, and Channel 2 will be measuring Vc.

   On your oscilloscope, display both the Vs and Vc signals simultaneously. To do this, press the "dual " button on the oscilloscope. Also, set the ground reference (by vertically centering both signals like part 1f).
    

   1. Once the Vs and Vc waveforms are properly displayed, use the vertical cursors to measure the frequency and period of each wave.  Note that each waveform has the same frequency and period.  Then, using your input waveform as the reference, measure the time difference between it and the output waveform. This time delay is the tmax value that you have been introduced to in class.   Convert this value to degrees using equation 3 and write a sinusoidal formula for Vc based on the information you've gathered in this step.

      
       

      t_max = -phase * T / 360         (3)

      
      

   2. Sketch and fully label (axes labels, t_max point, Vp, -Vp, and the period) the two waveforms in your lab book, on the same graph.

Questions
 

1. Is there a difference between peak to peak voltage and peak voltage?  Explain your answer.

   
    

2. If a waveform has a period of 10 ms, what is its frequency?  If a waveform has a frequency of 25 KHz, what is its period?

   
    

3. Describe the relative position the cursors should be in if you wanted to measure the peak voltage of a period sinusoid.  Describe their position if you wanted to measure the period of the waveform.  Describe their position if you wanted to measure the peak-to-peak voltage of the waveform.

Copyright 2002, New Mexico Tech