DSO Familiarization Activities

It is assumed that you have read the introduction and completed the Pre-Lab Quiz

If you have not done so, read the introduction before continuing.

Now that you have read the introduction, it is time to become familiar with the DSO.

After each step turn the 'Soft Menu' Off unless instructed to leave it on.

  1. Turn on the ac power to the DSO.

  2. Connect a cable to the Channel 1 input connector.
  3. Set you scope for Channel 1 only (if necessary, turn it on, or turn off Channel 2)

  4. Set your Channel 1 Volt per Division to 100 mV/div.
  5. Set your Time per Division to 5 milliseconds per division.
  6. Set your Trigger Level to 0 V by pressing in on the 'Trigger' knob until it 'click's and then release.
  7. Record in your notebook what you observe in the following cases:  (Explain what you did and what you observe - i.e. 'With the ends clipped together, I ...')
    1. The two ends of the cable clipped together.
    2. The two ends not touching - you or anything metallic.
    3. Your finger touches the metal part of the red clip.
    4. Repeat a), b), and c) after changing the V/div to 1.00 V/div.
  8. Set your  Volts per Division to 1V per division and your Time per Division to 1 millisecond per division.
  9. Set  your 'Coupling' to 'GND' and adjust your vertical position until the trace is along the middle line of the grid.  This sets the center line to be 0 V.   (A short cut to this is to press and release the Ch. 1 position knob.)
  10. Set your Channel 1 Coupling to 'DC'.  You have a battery in a plastic holder with two metal clips.  Place your black clip on the negative side of the battery. 
    1. Touch your red wire to the positive terminal of the battery. Record your observations.
    2.  Move the black lead to the positive end of the battery and repeat. 
    3. Set your Channel 1 'Coupling' to 'AC' and repeat the previous two tests. What do you conclude that AC coupling does?
  11. Switch the TIME/DIV control to 100ms. Set your trigger level to zero by pressing and releasing the 'Trigger Level' knob. You should now be seeing a line sweep slowly across the screen taking about a second to go across once (each division is covered in 0.1 seconds.)
    Connect your Channel 1 leads to the solenoid provided. Generate a voltage in the coil by moving a bar magnet in and out of the coil. Observe the signal on the oscilloscope. You may need to reduce the Volts/Div control. Describe the appearance of the trace. How large a voltage can you generate? What determines the size of the voltage?
  12. Connect the black or bare clip to the leftmost of the two metal protrusions just below the round 'Print' button - there is a symbol that looks a bit like a rake beside it.  Connect the red clip to the remaining metal protrusion.  (hint:  set your time/div to about 2 ms/div as a starting point)
    1. Describe what you observe.
    2. Set your trigger level to approximately one-third of the height of the waveform.  Does the displayed wave change?  If so, how?
    3. Set your trigger level so that it is above the top of waveform.  Does the displayed wave change?  If so, how?
    4. Adjust your Time per Division until you have a waveform that 1 period occupies more than 4 horizontal divisions and measure the period in divisions.
    5. Use your Time per Division value to calculate the period in seconds and the frequency in Hertz.
  13. Decrease the Channel 1 Volts per division value until you have the tallest waveform that will fit on the screen vertically. (You may have to adjust the vertical position of the trace in the process). 
  14. Place the lower portion of the trace on a grid line.  Use the Horizontal Position knob to shift the waveform until the upper part crosses across the vertical center line. 
    1. Measure the peak-to-peak amplitude in Divisions.
    2. Use the Volts per Division value to calculate the peak-to-peak voltage.  Now you have measured DV between the top and bottom parts of the waveform, but you still don't know the actual voltages. For instance, if you measure 10V peak to peak, the bottom might be 5V and the top 15V or the bottom could be -5V and the top 5V.  Often knowing DV is all we need, but not always.
  15.  To know the actual voltages we need to determine where the 0V reference is.  Press the green 'CH1' button, push the 'Soft Key' to the right of 'Coupling', rotate the selection knob to 'GND' and press the 'Soft Key'' again.   Adjust the Vertical Position for Channel 1 until the line is centered on the grid line one division above the bottom of the screen to set that line as 0V. Set the Channel 1 Coupling to 'DC'.  What are the voltages of the top and bottom portion of the signal?
  16. Use GND Coupling again to move the zero volt location back to the center line. Go back to DC Coupling. - If needed, adjust your Volt per division until the entire waveform is on the screen. Change the Coupling to AC.  Describe what happened.  Is this consistent with what you saw in step 10?
  17. Before moving on to using both Channels, let's try one more thing.  Remove the clip connecting the black or bare wire to the left metal protrusion.  How does the display change?  Why do you think this is the case?
  18. Connect your battery, lamp, and two resistors as shown in the figures below.  You will connecting both channels to the circuit, so make sure that Channel 2 is active.  Both should be set to 500 mV/div for a starting point. 
    1. Connect your scope as in 'A' and record your values.  Compute and record the voltage across R1.  Comment on the lamp brightness (if any).
    2. Change your connections to those shown in 'B' and record your values.  Comment on the lamp brightness (if any).
    3. Change your connections to those shown in 'C' and record your values.  Comment on the lamp brightness (if any).
    4. If the lamp glowed in a, b, or c, explain how this is possible since the values of the resistors are so high that not enough current can pass through the lamp to make it glow with the DSO disconnected.

     

     
    'A' 'B' 'C'

     

  19. Turn off Channel 2. 

Write a few sentences about what you observed in the tests.

Familiarization with the Function Generator

The next steps will give you some familiarity with the function generator that is built into the B&K Precision 2540-B DSO. 

  1. Remove your test lead cable from the Channel 1 BNC Jack.  Attach the ~ 20 cm long cable between the Channel 1 input and the Function Generator output. 

We want to set the function generator for a sine wave of a specific amplitude and frequency - in this case  2.00 V peak-to-peak and 1822 kHz.

  1. With the experience you have adjusting the Volts per Div and the Time per Div, you should have a feel for how the DSOs menus work by now.  The only new thing is using the 'Multi-Select' knob to pick a value and the < > switch below it to move one digit to the left or right.  The item to be changed by the 'Multi-Select' knob will be in red. A  'Press and Release' of the 'Multi-Select' will enter your value. Set the frequency and amplitude to the values given above before proceeding.
  2. Press the 'ON/OFF' button and it should turn green.  You will have a display on your screen that will require changing your Time per Div and possibly your Volt per Div.  Use these adjustments to find a display that covers more than 3 division from peak-to-peak and more than 4 divisions for 1 period.
    1. Record your Volts/Div, Time/Div, # of Div peak-to-peak, and # of Div in the period.
    2. Compute your peak-to-peak voltage and your frequency in Hz and compare it to the value you set.  Calculate the percent error in the Amplitude and the frequency.
  3. Now we will let the DSO measure the same quantities for us.  Press the 'Measure' button.  Press the 'Soft Key' by 'Source' until Ch 1 is visible.  Press the 'Voltage' 'Soft Key', and a number of possible voltage measurements will be shown.  Choose the peak-to-peak voltage by pressing its 'Soft Key'.  The value will be shown in yellow near the bottom of the display.
    1. Record the value in your notebook and compare it to the value you measured using the grid with the divisions.
    1. Next we will have the DSO measure the RMS value of the voltage.  Choose 'Voltage' from the 'Measurement' 'Soft Menu' and choose the Vrms value. Hide the menu.
      1. Record your value and compare the the Vrms value you would expect for a sine wave.  (hint Vp = 1.414 Vrms)
    2. Next we will determine the frequency of the sine wave.  On the measurement 'Soft Menu' select 'Time' and then 'Period'.  You might have to hide the menu to read the value in yellow for Channel 1 at the bottom of your display. 
      1. Record this value, convert to a frequency and compare the set frequency, frequency measured by the DSO, and the frequency that you measured.
    3. Go back to the Function generator and choose a frequency near 1 kHz.  Change Output to 'Built In - Arb', then go down to Waveform and select one of the many options.  Set your Amplitude to 1 Vrms (use the function generator - the relationship between Vp and Vrms will be different than for a sine function).  Adjust your Time / Div until two periods are shown.  Adjust your Volts / Div until the trace is more than 3 divisions tall peak-to-peak.
      1. Make a careful sketch in your lab notebook of the waveform displayed.  Be sure to include your Volts / Div and Time / Div values.
    4. Turn the Function Generator output off, and turn off the DSO.

    5. Be sure to include a conclusion where you reflect on what you have learned today.

     

     

     

     

    last modified 19 April, 2017