This lab aims to teach students how to measure AC voltage waveforms using an oscilloscope. The document outlines the objectives, equipment, background concepts and procedures for the lab. Students will connect a function generator output to an oscilloscope and measure peak-to-peak voltage, peak voltage, and period of waveforms at different time/division and frequency settings. Calculations of rms voltage, average voltage, peak factor, and form factor will be performed. Observations will be made by increasing and decreasing the applied frequency.

1. ET201 - Electrical Circuits 1
LABORATORY 1 AC VOLTAGE MEASUREMENT
1.0)OBJECTIVES:
At the of the lab, students should be able to :
1.1 Identify common oscilloscope controls
1.2 Display AC waveform on an oscilloscope
1.3 Measure the peak-to-peak voltage, the peak voltage, frequency and the periodic time of AC waveform
2.0)EQUIPMENTS:
2.1 Oscilloscope
2.2 Function generator
2.3 Multimeter
3.0)DESCRIPTION AND BACKGROUND
Voltage Measurements
Voltage is the amount of electric potential, expressed in volts, between two points in a circuit. Usually one
of these points is ground (zero volts) but not always. Voltages can also be measured from peak-to-peak from the
maximum point of a signal to its minimum point. You must be careful to specify which voltage you mean.
The oscilloscope is primarily a voltage-measuring device. Once you have measured the voltage, other
quantities are just a calculation away.
Figure 1 shows the voltage of one peak, V p and the peak-to-peak voltage Vp-p, which is usually twice Vp.
Use the rms (root-mean-square) voltage, Vrms to calculate the power of an AC signal.
Figure 3.1: Voltage Peak and Peak-to-peak Voltage
You take voltage measurements by counting the number of divisions a waveform spans on the oscilloscope's
vertical scale. Adjusting the signal to cover most of the screen vertically, then taking the measurement along the
center vertical graticule line having the smaller divisions makes for the best voltage measurements. The more
screen area you use, the more accurately you can read from the screen.

2. ET201 - Electrical Circuits 2
Figure 2: Measure Voltage on the Center Vertical Graticule Line
Formula:
1. V p − p = 2V p (volts )
Vp
2. Vrms = 0.707V p @ (volts )
2
3. Vav = 0.637V p (volts )
rms value
4. Form factor = = 1.11
average value
peak value
5. Peak factor = = 1.414
0.707 peak value
Time and Frequency Measurements
You take time measurements using the horizontal scale of the oscilloscope. Time measurements
include measuring the period, pulse width, and timing of pulses. Frequency is the reciprocal of the period,
so once you know the period, the frequency is one divided by the period. Like voltage measurements,
time measurements are more accurate when you adjust the portion of the signal to be measured to cover a
large area of the screen. Taking time measurement along the center horizontal graticule line, having
smaller divisions, makes for the best time measurements. (See Figure 3.)
Figure 3 : Measure Time on the Center Horizontal
Graticule Line

3. ET201 - Electrical Circuits 3
Formula:
1
f = ( Hertz )
T
1
T = (sec onds )
f
4.0)PROCEDURES :
1. Connect output from function generator to channel 1 oscilloscope as shown in Figure 4.1
Function
Generator
Osciloscope
Figure 4.1
2. Set the frequency of the function generator to 100 Hz and the voltage V1 to 6V as indicated on the multimeter
3. Set the main time/div setting to 20ms/div and delay time/div setting to 10ms/div. Draw the waveform as seen on
the screen, in Figure 5.1. Measure the peak-to-peak voltage, the peak voltage and the periodic time of
waveform.
4. Change the delay time/div setting to 5ms/div. Draw the waveform in Figure 5.2
5. Then change the main time to 1ms/div. Draw the waveform in Figure 5.3.
6. Measure the peak-to-peak voltage, the peak voltage and the periodic time of waveform for step 4 and 5.
7. Set the delay time/div back to 10ms/div. Increase and decrease the frequency of the applied voltage. Write your
observation.

4. ET201 - Electrical Circuits 4
5.0)RESULTS:
5.1 For step 3
Figure 5.1
Vp-p = _______________________________________________________
Vp = _______________________________________________________
T = _______________________________________________________
(8m)
5.2 For step 4
Figure 5.2

5. ET201 - Electrical Circuits 5
Vp-p = _______________________________________________________
Vp = _______________________________________________________
T = _______________________________________________________
(8m)
5.3 For step 5
Figure 5.3
Vp-p = _______________________________________________________
Vp = _______________________________________________________
T = _______________________________________________________
(8m)
Observation
.
.
.
.
Lecturer’s name:
Signature : Date:

6. ET201 - Electrical Circuits 6
QUESTION
1. Calculate the rms voltage, average voltage, peak factor and form factor for each waveform in step 3 and 4
(8m)
2. Determine the average value of a waveform that measured 16Vp
(2m)
3. What is the frequency of a waveform that has a period of 200µs?
(2m)
DISCUSSION
(5m)
CONCLUSIONS:
(2m)
Score :
Lecturer’s name :
Signature : Date :
;