Additional Instructions for “Rangefinder” Lab

Procedure:

  • Function Generator (Agilent 33521A 1Ch-250MSa/s 30MHz)

To obtain the required output from the function generator, follow the steps given below:

  1. To adjust the output channel specifications, press CHANNEL. Then choose “Output Load” to specify the ‘Channel Output Load’ of 8 ohm (input impedance of a standard speaker).
  2. To select the shape of the output voltage, press WAVEFORMS. Then choose “Square” as the shape of the waveform.
  3. To select the parameters of the waveform selected, press PARAMETERS. Then choose “Frequency” to be 2 KHz and “Amplitude” as 2.5 Vpp. Select a “Duty Cycle” of 50%. Set “Offset” to 0.0V and “Phase” to 0 degrees.
  4. To obtain the output voltage waveform for desired duration, do the following adjustments. Press BURST to enter the burst mode. Choose “On” to enable the burst output of the function generator. Enter the “# of Cycles” as 1. Next, press TRIGGER beside the SWEEP button, above BURST) to make the ‘Source’ of the Trigger as ‘Manual’.
  5. Press CHANNELand choose “Output ON” so that function generator will now generate a square shaped burst of 2KHz frequency whenever the TRIGGER is pressed.

Figure 1: Display of the transmitted burst (CH1) and sound wave received by mic (CH2)

  • Mixed Signal Oscilloscope (Agilent MSO7034B)

To observe the input voltage given to the circuit and output voltage of the circuit on the oscilloscope, follow the steps given below:

  1. After switching on the oscilloscope, press DEFAULT. Press ACQUIRE to select “High Resolution” acquisition of the voltages at both the channels.
  2. Connect the output of the function generator to CH1 of the scope as well as tthe speaker.
  3. Connect the output of the microphone circuit implemented to CH2 of the scope.
  4. To capture the single burst generated by the function generator, one needs to set the “Trigger” level of the CH1.

Whenever the voltage at CH1 rises above Trigger level specified (indicated as “T on the scope screen), the event will be captured by the scope. Set the trigger level of CH1 appropriately.

Press TRIGGER and set the trigger level as specified above using the knob beside the TRIGGER button. Make sure that “Trigger Type” is ‘Edge’, “Source” is ‘Source 2’ and “Slope” is ‘Rising Edge’.(You will find these options at the bottom of the scope screen when you press TRIGGER.)

  1. Select the trigger mode by pressing MODE/COUPLING button right next to Trigger knob and choosing the “Mode” as ‘Normal’.
  2. Now press RUN/SINGLE so that the waveforms at both the channels are displayed. Press SINGLE to prepare the scope to capture the burst from the function generator. After pressing single, the button will go yellow and the screen will become blank, do not be alarmed!
  3. Now, whenever you are ready with appropriate speaker-mic arrangement, press TRIGGER on the function generator panel to generate a burst.
  4. The scope will capture the voltages at both channels when the voltage at CH1 crosses the Trigger level set.
  5. To measure the time difference between the occurrence of burst and its detection by the mic, press CURSORS on the oscilloscope panel. Adjust the axes positions (X1, X2) by using the knob beside the CURSORS button to show correct time difference.
  6. Happy observing! ;)
  • Link for mic circuit:

Created by Chaitali Gondhalekar, Nov 12, 2013Page 1