Function Generators and Oscilloscopes/ write lab report for this experiment

Laboratory Assignment

Identify the model of the function generator and oscilloscope on your bench.

Function Generator (Model no.): _________________
Oscilloscope (Model no.): ____________________

Turn on the function generator and oscilloscope. Connect the function generator to the oscilloscope using a BNC
cable as shown in Figure 1.

Figure 1: Connect output channel 1 of the function generator to channel 1 of the oscilloscope.
Part I: Generating a signal using the function generator

Configure the function generator to generate a sinusoidal waveform of frequency 10 kHz and amplitude 2Vpp using
the procedure below. Please refer to the diagram of the front panel on the last page of this manual (Figure App.1) if
you are having trouble finding any button.

1. Set the frequency to 10 kHz – Press the “Parameters” button on the front panel of the function generator.
   (Located under #5 Fixed Function Buttons in Figure App.1). Select “Frequency” by pressing the button
   below the word ‘Frequency’ (#4 in Figure App.1). Enter 10 using the numeric keypad and select kHz.
   Note: Any option displayed on the screen can be selected using the softkeys below the screen.
2. Set the amplitude to 2 Vpp – Select “Amplitude” by pressing the button below the word ‘Amplitude’ (#4 in
   Figure App.1). Use the keypad to enter the number 2 and select Vpp.
3. Verify the impedance and turn on the output – Select the output by pressing “Channel” under channel setup
   (#9 in Figure App.1). Press the key below “Output Load” and verify that “CH1 Output Load” is set to 50Ω
   and press “Done”. Turn on the output by selecting “Output” on the screen.
4. The signal generator can be modeled by an equivalent circuit consisting of an AC voltage source in series
   with an impedance called the source impedance, Zs, as shown in Figure 2. Depending on the output load
   setting, Zout, the internal source voltage, Vs is scaled in order to obtain the desired voltage across the output
   terminal using the equation for a simple voltage divider given below:
   Vout = VsZout
   Zs +Zout
   

Laboratory #3

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If a 50 Ω load is connected to the output, calculate the source voltage, Vs such that Vout = 2 Vpp. (Hint: Use
the equation above). Vs = ______________

Figure 2: Equivalent circuit of the function generator.
Before proceeding to the next part of the laboratory, ask your TA to check the waveform displayed on

your oscilloscope and obtain his/her signature on the first page.
Part II: Measuring the signal using the oscilloscope

You will need to refer to the document ‘WAMI Lab Oscilloscopes Operation Guide’ for the following steps. Please
download the document from canvas.

1. For your oscilloscope, refer to the oscilloscope operation guide and set the oscilloscope impedance to 50 Ω.
This sets the input impedance of the oscilloscope, and for this experiment plays the role of the Zout in Figure
2.

Note: In practice, the input port of the oscilloscope also consists of a parallel capacitance. The effects of this
capacitance are not significant in this experiment but you will encounter some effects of this capacitance
later in the semester.

1. Setting the time axis –
   1. What is the period of the waveform generated by the function generator?
      Period = ______________
   2. Display two periods of the signal on the oscilloscope display.
      The corresponding scale of the x-axis (in μs/div) is __________
2. Setting the y-axis (voltage axis) – use the instructions in the document and set the voltage axis to 0.5
   V/division.
3. If the signal is not stable on the screen, refer to the “Triggering the Oscilloscope” section of the document
   or ask your TA.
4. Display cursors and measure the signal characteristics using the cursors –
   1. Time between two consecutive voltage maxima in the signal = ________
   2. Time between two consecutive voltage minima in the signal = ________
   3. Minimum time difference between a voltage minima and maxima = _______
   4. Frequency of the signal =______

Laboratory #3

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1. Peak to peak voltage of the signal = ______
2. Peak voltage of the signal = _______

1. Use the in-built measurement option in the oscilloscope to measure the following signal characteristics. You
   can turn off the cursors for this step.
   1. Period = ______
   2. Frequency = ______
   3. RMS voltage = _______
2. Before proceeding to the next part of the laboratory, ask your TA to check the waveform displayed
   on your oscilloscope and obtain his/her signature on the first page.

Part III: Effects of impedance settings on the oscilloscope

Study the effect of two oscilloscope impedance settings, 1 MΩ and 50 Ω, on the accuracy of the measurement.

1. Using the procedures in Part I, set up the function generator to generate a 3 kHz sinusoidal signal of
   amplitude 2 Vpp.
2. Measure the frequency and amplitude of the signal using the oscilloscope.
3. Change the impedance of the oscilloscope to 1 MΩ and measure the frequency and amplitude of the signal.
   Refer to the oscilloscope manual for instructions on how to change the impedance.
4. Make similar measurements for signals with different characteristics by filling in Table I. Indicate the units
   clearly. You will see that measurements are accurate only when the source and load impedances are
   matched.
   Table I: Effect of oscilloscope impedance setting on measurement accuracy.

Laboratory #3

Measured frequency (kHz)
Measured peak to peak voltage (V)

Frequency (set on function generator)	Amplitude (Set on function generator)	50 Ω Impedance Setting			1 MΩ Impedance Setting
		Measured Frequency	Measured Period	Measured Vpp	Measured Frequency	Measured Period	Measured Vpp
50 Hz	1 Vpp
750 Hz	3 Vpp
1.5 kHz	2 Vpp
5 kHz	500 mVpp

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Before proceeding to the next part of the laboratory, ask your TA to check the waveform displayed on
your oscilloscope and obtain his/her signature on the first page.

Part III: Dynamic range

Dynamic range of an instrument is the ratio between largest and smallest values of a quantity that the instrument can
generate/measure. You will investigate if the dynamic range of the function generator lies within the dynamic range
of the oscilloscope. In other words, you will measure if the oscilloscope can accurately measure any signal that is
generated by the function generator.

1. Change frequency and study measurement accuracy: Generate a 2 Vpp sinusoidal signal and vary its
frequency. Measure the frequency and amplitude of the signal on the oscilloscope and fill in Table II. Make
sure that the impedance of the oscilloscope is set to 50 Ω and indicate the units clearly in the table.

Table II: Change frequency and track oscilloscope measurement accuracy. Vpp = 2V

Laboratory #3

Observations

Does the impedance setting of the oscilloscope affect the measurement of frequency? Does it affect the
voltage measurement? Why/why not? Hint

see attached file