ee043 electronic oscilloscope pr inst

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SRI LANKA INSTITUTE of ADVANCED TECHNOLOGICAL EDUCATION

Training Unit

Electronic OscilloscopePractice

No: EE 043

INDUSTRIETECHNIKINDUSTRIETECHNIK

ELECTRICAL and ELECTRONICENGINEERING

Instructor Manual


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Training UnitElectronic Oscilloscope

Practical Part

No.: EE 043

Edition: 2008All Rights Reserved

Editor: MCE Industrietechnik Linz GmbH & CoEducation and Training Systems, DM-1Lunzerstrasse 64 P.O.Box 36, A 4031 Linz / AustriaTel. (+ 43 / 732) 6987 – 3475Fax (+ 43 / 732) 6980 – 4271Website: www.mcelinz.com


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ELECTRONIC OSCILLOSCOPE

CONTENTS Page

LEARNING OBJECTIVES ........................... .......................... ........................... ...................4

PRACTICAL EXERCISE 1

Measuring direct voltage with an oscilloscope in XY operation. .......................... ................5


Measuring a sinusoidal alternating voltage with an oscilloscope.........................................7


Representation of two alternating voltages, in-phase and out-of-phase by 180°

respectively in x-y operation .......................... ......................... ............................ .................9


Representation of two alternating voltages with a 90° phase displacement in x-y operation

...........................................................................................................................................11

PRACTICAL EXERCISE 5Measuring voltage with an oscilloscope. ...................... ........................ .......................... ...13


Determining time and frequency........................................................................................16


Checking the range of audibility.........................................................................................21


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Current-voltage curve of a resistance................................................................................23

PRACTICAL TEST ........................ ........................... ......................... ........................... .....48


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LEARNING OBJECTIVES

The student should…

explain how the control elements of an oscilloscope function.

select the mode of Operation according to requirements.

explain with which voltages the x and y-input must be connected to give a true

representation of a periodic process.

determine the peak-to-peak and effective value of an alternating voltage using the

oscilloscope.

determine the periodic time of a signal and deduce the frequency. measure current indirectly using the oscilloscope.


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ELECTRONIC OSCILLOSCOPE 2


Measuring direct voltage with an oscilloscope in XY operation.

1. TASK

Establish a relationship between the direct voltage input and the Y deflection of an

oscilloscope.

2. EQUIPMENT

Mains unit or 4.5 V pocket-lamp battery.

Double-channel oscilloscope (suitable for X-Y representation).

Test cable.

3. CARRY-OUT THE EXERCISE


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- Turn on the oscilloscope.

- Wait 5 minutes until the oscilloscope temperature is stabilized.

- Using vertical positioning control, bring the horizontal trace to the lowest line on the

screen.

- Apply 4.5 VDC voltage to the vertical input of the oscilloscope.

- Measure the voltage and draw the displayed trace on the raster.


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Measuring a sinusoidal alternating voltage with an oscilloscope.

1. TASK

Determine the peak-to-peak value of a sinusoidal alternating voltage with the oscilloscope.

2. EQUIPMENT

Function generator.

Double-channel oscilloscope.

Test cable.



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- Turn on the oscilloscope.

- Wait 5 minutes until the oscilloscope temperature is stabilized.

- Bring the horizontal trace to the centre line of the screen.

- Adjust the function generator output to 10 volts peak-to-peak.

- Measure the voltage with the oscilloscope.

- Measure the voltage and, draw the displayed trace on the raster.


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Representation of two alternating voltages, in-phase and out-of-phase by 180°

respectively in x-y operation

1. TASK

Set up a measuring circuit to represent two sinusoidal alternating voltages in-phase and

out-of-phase by 180°.

2. EQUIPMENT

Alternating voltage supply (function generator).

Double-channel oscilloscope.

Test cable.


Measuring circuits


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- Draw graphically the resultant trace:

- Set the mode selector to X-Y.

- Set the vertical and horizontal gain selectors to 1V/Div.

- Apply two signals (peak-to-peak 7 V) to the inputs with zero and 180° phase

displacement.

- Compare the represented traces with that obtained from graphically plotting.


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Representation of two alternating voltages with a 90° phase displacement in x-y

operation

1. TASK

Set up a measuring circuit to be able to represent two alternating voltages with a 90°

phase displacement.

2. EQUIPMENT

Alternating voltage supply.

Capacitor 47 µF

Resistor 10 Ohms 2 W.

Oscilloscope.

Circuit building board.

Test cable.


- Draw graphically the result trace.

- Construct the circuit.

- Switch the mode selector to X-Y.

- Set both amplifier gain selectors to 1V/DIV.

- Observe the trace on the screen.- Vary the AMP/DIV setting, the form of the resultant trace changes.


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Measuring voltage with an oscilloscope.

1. TASK

Determine the peak-to-peak value of three signals and calculate their effective value.

2. EQUIPMENT

Function generator.

Oscilloscope.

Connection lines.


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The following two signals appear on the screen:

- Note the setting of the AMP/DIV controls.

- Measure the voltages.

- Calculate the effective voltages.

Calculation for Signals 1 and 2:


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- Measure the maximum voltage in the figure shown below:


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Determining time and frequency.

1. TASK

Determine the period duration of the three represented signals and calculate the

frequency.

2. EQUIPMENT

Function generator.

Oscilloscope.

Test cable.


The following two signals are represented on the screen:


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Determine the periodic times of both signals.

The time base switch is set to ...

The time base is set to 0.5 ms/div. Determine the periodic time and the frequency of the

triangular signal.


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The time base is set to 5 ms/div. Determine once again the period duration and frequency

of the square-wave signal.


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Indirect current measurement.

1. TASK

- Measure the voltage drop across the measuring resistance 10 with the help of the

oscilloscope.

- Determine the current by indirect means.

- Repeat the experiment with a 100 and a 100 0 resistance and compare the measured

values with the indirectly measured values.

2. EQUIPMENT

P1 millimetre

Rmeas 1 = 1 Ohm

Rmeas 2 = 10 Ohm

Rmeas 3 = 100 Ohm

L = lamp 15 V/82 mA

Oscilloscope with sensing head

Circuit building board


- Set up the circuit:

- Measure the current directly (P1).

- Measure the voltage drop across the measuring resistances.- Determine the current indirectly and record the values in the table of measured values.


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Measurement table:

This method can be used for both direct and alternating current.


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Checking the range of audibility.

1. TASK

The area of audibility of the human ear is to be checked with the help of a function

generator and a loudspeaker.

2. EQUIPMENT

Function generator

Oscilloscope

Loudspeaker 4 or 8 Ohm

Protective resistor 47 Ohm

3. CIRCUIT DIAGRAM


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- Set the frequency of the function generator to 1 kHz.

- Increase the height of the amplitude until a clearly audible signal is heard.

- Adjust the vertical and horizontal amplifier gains to obtain a clearly assessable signal.

- Increase or reduce the frequency until the signal is no longer heard. Measure the

periodic times for both frequencies.

Results:

Vibrations within a given range generate sounds which are audible to the human ear.

Depending on each individual person, this range is situated between 16 Hz and 20 kHz.


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Current-voltage curve of a resistance.

1. TASK

The object is to represent the current-voltage curve of a resistance on an oscilloscope.

2. EQUIPMENT

R = 10 kOhm

Rmeas = 100 Ohm

Oscilloscope

Circuit building board

Voltage source 0 - 30 V.


- Set up the circuit.

- Select the "XY" mode of operation. This switches off the time deflection. The CH 1 (X)

amplifier is now connected to the time deflector plates. The two amplifiers are now

available for the X and Y directions.


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Draw the oscillogram onto the screen grid represented below.


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Electronic Oscilloscope 2

Instructions for Practical Exercises


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INSTRUCTION for practical exercise No. 1:

Measuring direct voltage with an oscilloscope


- Select a direct voltage of approx. 4.5 V.

- Switch on the oscilloscope.

- Switch the Input coupling to "GND".

- Adjust the "focus" and "intensity" correctly.

- Set the X-Y mode of operation.

- Set the point with the "position" potentiometer on the lowest grid line.- Now switch the input coupling to "DC".

- Connect the direct voltage source with the oscilloscope input (minus to earth).

- Set the vertical gain selector to obtain the largest possible deflection (1 V/D1V).

- Draw the oscillogram onto the grid.

Explanation of the oscillogram

What is the magnitude of the direct voltage?

U = AFy x Y = 1 x 4.5 = 4.5 V

U = voltage to be measured

AFy = voltage sensitivity set on the vertical gain

Y = Y-deflection in cm or graduation lines


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INSTRUCTION for practical exercise No. 2

Measuring a sinusoidal alternating voltage with an oscilloscope



- Make sure that "focus" and "intensity" are correctly set.

- Switch the Input coupling to "GND"

- Set the X-Y mode of Operation.

- Set the point to the centre of the grid (x-position, y-position).

- Switch the input coupling to "AC".- Switch on the function generator.

- Turn the amplitude potentiometer to "0".

- Connect the output of the function generator with the input of the oscilloscope.

Attention: connect the ground of the oscilloscope with the ground of the function

generator.

- Use the amplitude potentiometer on the function generator to set the output signal to

approx. 10 V peak-to-peak (approx. 50 Hz).

- Set the vertical gain selector to obtain the greatest possible deflection (2 V/Div).

- Draw the oscillogram onto the grid.


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Determine the peak-to-peak value of a voltage applied to an oscilloscope.

Upp = AFy x Y = 2 x 5 = 10 V

Upp = peak-to-peak value of the oscilloscope.

AFy = voltage sensitivity set on the range switch.

Y = Y-deflection in cm or divisions.

Now gradually alter the frequency to approx. 1 Hz and observe the screen. Discuss your

observation.


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Representation of two alternating voltages, in phase and out-of phase by 180°

respectively in x-y operation


- Construct the oscillogram onto the grid.

(Connect points 1-13 from the x and y sign& respectively).


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- Check the constructed oscillogram experimentally with the help of measuring

arrangement.

- Put the oscilloscope and the function generator into operation (f = 1 - 100 Hz).

- Connect the output of the function generator to the vertical input of the oscilloscope

(V = 7 V).

- Set the vertical gain selector to 1 V/Div and set 7 graduation lines on the screen

(VPP = 7 V).

- Set the mode selector to X-Y, now you observe a vertical line on the screen.

- Disconnect the vertical input signal and apply seven volts to the horizontal Input (X-

input). As the mode selector is set to X-Y, a horizontal line is displayed on the

oscilloscope.


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- When both inputs are 7 volts, the displayed trace will be as straight as shown below.

- Compare the constructed picture with the oscilloscope picture.

- Carry out the same task a second time, but changing the measuring arrangement for

1800 phase displacement. Draw the oscillograms with a felt pen of another colour or in

a dotted line.


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INSTRUCT1ON for practical exercise No. 4

Representation of two alternating voltages with a 90° phase displacement in X-Y

operation.


- Draw graphically the resultant curve on the raster below when vertical and horizontal

inputs of the oscilloscope are fed with two alternating signals with equal amplitude but

with 90° phase displacement.


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- Connect up the circuit.

- Switch the mode selector to X-Y.

- Adjust both gain selectors to 1 V/Div.

- As the resistance of the capacitor is larger than the resistance R, the applied signals to

the oscilloscope are not equal in amplitude, an ellipse is displayed on the screen. By

adjusting the horizontal input gain, we can obtain a circular trace on the screen.


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Measuring voltage with an oscilloscope.

1. CARRY-OUT THE EXERC1SE

Calculations:

Signal 1


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- The peak-to-peak voltage of the following wave form is

Y = 6 U pp = 0.1 x 6 = 0.6 V

AFy = 0.1 V/div U eff = U max x 1 = 0.3 x 1 = 0.3 V


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Determining time and frequency.



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INSTRUCTION for practical exercise No.7

Indirect current measurement


- Connect up the following circuit.

- Switch on the oscilloscope and the power supply.

- Apply 15 V to the circuit.

- Keep the supply voltage constant during the measurements.

- Measure the voltage drop across the R meas .

- Measure the current (P1).

- Calculate the current / = U meas / R meas

- Enter the measured values onto the table.


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- Repeat the measurements for R meas = 10 Ω and 100 Ω .

- Compare the measured and calculated current values.

Measurement table


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Checking the range of audibility.


- Construct the circuit.

- Set the function generator signal frequency to 1 kHz, then increase the signal voltage

until a clear audible signal is heard.

- The output of the function generator is also connected to the oscilloscope and thevertical gain and the time base are set so that a clear wave form is displayed on the

screen.

- Reduce gradually the frequency until no audible signal is heard.

Record this frequency (f 1)

- Increase the frequency until no audible signal is heard.

Record this frequency (f 2).

- The frequency range of audibility is from f 1 to f 2 .


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Current-voltage curve of a resistance


- Connect-up the circuit.


- Switch the mode selector to the X-Y position.

- Adjust the gains to obtain a good display on the screen.


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- Draw the oscillogram onto the screen grid represented below.

Attention:

The voltage on the X-axis is given directly by the V/cm setting.

On the Y-axis the voltage drop must first be converted into Current.


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Electronic Oscilloscope

Evaluation Sheet for Practical Exercises


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EVALUATION SHEET


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KEY TO EVALUATION

PER CENT MARK

88 – 100 1

75 – 87 2

62 – 74 3

50 – 61 4

0 – 49 5


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EE043Electronic Oscilloscope

Practical Tests


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EE 043


PRACTICAL TEST

Measuring voltage - time and frequency.

1. TASK

- Calculate the time of a period, the frequency, the voltages Upp and Ueff

- Check the calculation with the practice Instrument.

2. EQUIPMENT

Signal generator

Oscilloscope

Connecting cables


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3. CARRY-OUT THE EXERC!SE

- On the oscilloscope the following picture is displayed.

The vertical and horizontal selectors are set in the following manner:


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Calculation:

- Check the calculation

Oscilloscope and signal generator operational block diagram

the equipment adjustments are as indicated below.Signal generator: f and U max according to calculation

Oscilloscope setting:

Ampl/div = 0.2 V/div

Time/div = 2 ms/div


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Draw the sine-wave on the screen indicated below, that would be displayed with the

equipment adjustments indicated above.


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EE 043


PRACTICAL TEST

(Solution)


The calculations are as follows:

Period Time: Peak-to-peak and efficiency voltage


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- Now apply a voltage Ueff = 0.35 V and f = 83 Hz to the oscilloscope input. Set the

Amp/div to 0.2 V/div and Time/div to 2 ms/div.

Displayed trace


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EE 043


EVALUATION SHEET TO PRACTICAL TEST

Calculation 4 x 10 Points 40 Points

Construction of exercise 10 Points

Checking the calculation with measurement 40 Points

Drawing the sine-wave on the screen 10 Points

TOTAL 100 Points


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ee043 electronic oscilloscope pr inst

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