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 on the top. 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 menu button enables/disables the channel, turn VOLTS/DIV knob).
Time / Division = 250us (Turn SECONDS/DIV knob).
Trigger Source = Channel 1 (Push TRIGGER MENU, select Channel 1 from the Source menu).
 

3. (For Tabor function generators) 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 10Vpp (peak-to-peak), 1 Khz sinusoidal wave.

 

 
 
 
 
 

          - Use the output arrows to select the sinusoidal wave pattern.

          - Highlight the Frequency option (FREQ under Display/Modify) and use the MODIFIER and RANGE controls to set an
            output frequency of 1 Khz.

          - Highlight the Amplitude option (AMPL) and adjust Vp (peak voltage) for 5 volts.
 

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 "buried" function generator settings, or the physcial connection.

 
6. Now, make sure the sinusoidal wave is vertically centered on your scope. Press the Ch 1 menu button, then select the Ground option under the Coupling submenu. The Channel 1 vertical position should be set to 0.00 divs (0.00V). If it is not, adjust using the "Vertical Position" knob.

 
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 adjusted using the "Horizontal Position".


You should now have a stable cosine wave with an amplitude of 5 volts, a phase shift of 0 degrees, and a frequency of 1 Khz (see equation 1) display on the oscilloscope. Have a lab TA verify this.

v(t) = 5 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, press Cursor, and then select Voltage under the Type submenu. Use the Vertical Position knobs to place the cursors at Vp and -Vp.  Under the delta submenu the peak to peak voltage will be recorded.  Repeat this process to measure the Peak Voltage.

 
2. Measure both the Period and Frequency of the waveform using the vertical cursors. To do this, press Cursor, and then select Time under the Type submenu. Use the Vertical Position knobs to again place the cursors. The delta submenu displays both the period and frequency measurements.

 
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 "Channel 2" menu to display the second channel (the first should already be enabled). Also, set the ground reference (by vertically centered 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.

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 2001, New Mexico Tech