Practice 4_AFC - Edgar Bello

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Index 
Objective 3 
Equipment 3 
Material 3 
Theoretical introduction 4 
Development of the practice 4 
 ​1.- Measurement of the adjustment signal 4 
 2.- Checking the operation of the signal generator. 6 
 3.- The oscilloscope as an X-Y plotter, with D.C 7 
 4.- The oscilloscope as an X-Y plotter, with A.C. 9 
Conclusions 11 
Evidence 12 
 
 
2 
 
“Oscilloscope’s use” 
Objective: 
At the end of the practice the student will be able to: 
 
• The operation of the oscilloscope controls. 
• Evaluate the adjustment signal for metal test tips from a general-purpose 
oscilloscope. 
• Operate a voltage signal generator in a sine, square and triangular function. 
• Measure DC voltage using the horizontal input or the vertical input of the 
oscilloscope. 
• Obtain and evaluate voltage vs time graphs in basic circuits to measure amplitudes, 
periods and frequencies of voltage signals. 
• Use the two vertical inputs of the oscilloscope to measure the phase shift between 
two sinusoidal signals using the Y (t) mode and that of the Lissajous figures in the 
XY mode. 
 
Equipment provided by the laboratory: 
1 Oscilloscope. 
1 Function generator. 
1 Variable voltage source. 
1 Multimeter. 
 
 Materials that students must bring: 
1 4.7 K​Ω​ resistor at ½ watt. 
2 10K​Ω​ ½ watt resistors. 
1 0.1 µF capacitor. 
1 breadboard. 
Wires for connection. 
3 Oscilloscope tips. 
1 Tip from BNC to BNC. 
4 banana-alligator tips. 
 
3 
 
I.- Theoretical Introduction. 
 
Oscilloscope working principle. 
The operation of this measuring instrument is similar to the TV receiver kinescopes: 
the electron gun (cathode) sends a beam to a screen covered with a phosphorescent 
material; during its journey, the beam goes through stages of focus (grids) and 
acceleration (anode attraction), in such a way that when hitting the screen a 
luminous point is produced, by conveniently located baffle plates, it is possible to 
modify the straight path of the electrons, both vertically and horizontally, allowing the 
display of various information. Allowing to observe details that by other ways, would 
be impossible to visualize. 
 
II.- Development of the Practice. 
 
II.1.- Measurement of the adjustment signal at the oscilloscope calibration test 
terminal. 
 
Power up the oscilloscope and locate the CALIBRATION test lead on the face of the 
oscilloscope. Connect this terminal to channel 1 (CH1), using an oscilloscope cable, 
and then select the trigger source (must be CH1). Adjust the voltage amplitude (volts 
/ div) and time base (time / div) controls to a scale that properly displays a full cycle 
of the calibration test signal. Draw the resulting signal on the graticule shown and 
report the characteristics of the signal obtained, both in amplitude and in frequency. 
 
 
 
 
 
 
 
 
 
4 
 
CHANNEL 1 CHANNEL 2 
Time / Div = ​ 250m ​Seg / Div Time / Div = ​ 250m ​Seg / Div 
Volts / Div = ​ 2 ​Volts / Div Volts / Div = ​ 5 ​Volts / Div 
 
Period T is calculated below: 
 
T = (time / div) X (Num. ofhorizontal divisions) 
 
For channel 1: For channel 2: 
 
T =​ 250 ​ X ​ 4m ​ Sec T = ​ 250 ​ X ​ 4m ​ Sec. 
T = 1000m Sec T = 1000m Sec 
 
The frequency value is calculated as follows: F = 1 / T 
 
For channel 1: For channel 2: 
 
F = 1 /​ 1000m ​Sec. =​ 1000 ​Hz. F = 1 /​ 1000m ​Sec. = ​1000 ​Hz. 
 
 
The value of the peak-to-peak voltage amplitude is calculated as follows: 
 
V = (volts / div) X (No. of vertical divisions) 
 
For channel 1: For channel 2: 
 
V = ​ 2 ​X​ 2.5 ​ = ​ 5 ​ Vpp V = ​ 5 ​ X​ 1 ​ = ​ 5 ​ Vpp 
 
Note: 
THE SIGNAL OF ADJUSTMENT, OF THE CALIBRATION TEST TERMINALS, IS 
GENERATED INTERNALLY BY THE OSCILLOSCOPE AND, THE VALUES OF 
5 
 
FREQUENCY AND AMPLITUDE MEASURED MUST CORRESPOND WITH THE 
LEGEND MARKED ON THE FRONT FACE. 
 
 
II. 2.- Checking the operation of the signal generator. 
 
II.2.1.- Energize the signal generator, connect its output terminal to the input of 
channel 1 of the oscilloscope, for this use its cable with BNC-BNC connectors. Set 
the frequency of the output signal on the generator to 10KHz and the amplitude to 10 
Vpp. Select the different waveforms that the function generator delivers and fill in the 
following table as requested. 
 
Function Amplitude Vpp 
(Volts) 
Period T (sec) Frequency F 
(Hz) 
Shape of the 
signal 
SENOIDAL 5.8 V 100 mS. 10 KHz 
TRIANGULAR 5.6 V 100 mS 10 KHz 
SQUARE 5.8 V 100 mS 10KHz 
6 
 
 
 
 
 
 
 
II.3.- The oscilloscope as an X-Y plotter, with D.C. 
 
The Cartesian displacement of the electron beam subject to different DC voltage 
polarities at the input terminals of the oscilloscope will be measured. 
7 
 
Put the oscilloscope in X-Y mode with the coupling selectors on both channels in the 
GND (ground) position. Use the X-POSITION and Y-POSITION controls to place the 
traces of both channels in the ORIGIN (the reference 0Vx, 0Vy), with the point in the 
center of the oscilloscope screen. 
 
Note: 
On some oscilloscopes this mode of operation is selected by turning the time base 
knob (TIME / DIV) to the X-Y position, on other models there is a button to select the 
mode. 
Subsequently, assemble the circuit shown in the following figure and, with the 
oscilloscope test leads connected to the points indicated in each case. Take the 
measurements below, with the oscilloscope's X and Y channel coupling selectors in 
the CD position. Draw the result of each of the measurements placing the 
corresponding number on the same graticule, using a different color for each case. 
 
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Measurements to be made with the aid of the oscilloscope probes: 
1.) Positive from channel X to point A and negative from channel X to point C. 
2.) Positive from channel Y to point B and negative from channel Y to point C. 
3.) Positive from channel X to point A, positive from channel Y to point B and 
negatives from both channels to point C. 
4.) Same connection as the previous point but with the inverted Y channel. 
5.) Positive from channel X to point B, positive from channel Y to point C, negatives 
from both channels to point A and inverted Y channel. 
 
II.4.- The oscilloscope as an X-Y plotter, with A.C. 
 
The phase angle (f) existing between the electrical input and output signals of an RC 
circuit, energized with a sinusoidal voltage, will be measured. 
The following figures show two methods for measuring the phase shift angle (f) and 
the equations for their calculation. The first is done using the oscilloscope as a 
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plotter with respect to time Y (t). The second mode is performed using the 
oscilloscope as the XY plotter and is known as the LISSAJOUS method. 
 
 
 
 f = (360 °) (a) / T f = ± sin-1 (B / A) 
 
Since it is a matter of measuring the phase angle (which is a function of time), it can 
be measured even when the variable controls for volts / div, both channel 1 and 
channel 2, are in a different position. Connect the oscilloscope to the following circuit 
and obtain the offset angle at R withrespect to the input signal using both methods 
and draw the resulting signals on the following graticules. 
 
Y (t) mode XY mode 
Volts / div = ___6.2_____ Volts / div = ____6______ 
Time / div = ____100m____ Time / div = ____400m______ 
 
 
 
 
 
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IV.- Conclusions 
 
Edgar Alejandro Bello Muñoz 
An oscilloscope is a device with great importance in electronics because it 
graphically represents electrical signals that can vary over time. 
Since we were working for the first time with alternating current, and it generates a 
signal that varies over time, the oscilloscope was used to visualize the elements of 
the generated signal, such as period, frequency, and peak-to-peak voltage. 
Another element of interest in this practice was the signal generator. It was used to 
supply the circuits made in the practice with the requested frequency, period and 
voltage values. 
 
Núñez González Angel Daniel 
The use of the oscilloscope is very important in this of the electronic circuits since 
they serve to show how the voltage behaves in different functions (sinusoidal, 
quadratic and triangular function) in alternating current. Throughout the previous 3 
practices, direct current circuits have been studied and in practice 4 we see how the 
behavior of the sinusoidal current is, how the values of voltage, frequency, period are 
obtained, among other things. 
The oscilloscope is also assisted with the one of a wave generator to create specific 
situations in this area, which helps to have more knowledge and problems that can 
already be found in professional practice. 
 
López Gracia Angel Emmanuel 
In this practice we learned two different ways to visualise how an oscilant electric 
wave behaves, how it can be represented and how it can interact with resistances, 
that, by the way, are not so different to the before interactions that we already 
studied with direct current. 
In an other hand, we did learn the basic use of an oscilloscope, what as matter of 
fact, was a bit difficult and interesting, we learned how the oscilloscope can read an 
electric beam and how we can interpret this reading. 
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