Lab Report 1 Updated

8/11/2019 Lab Report 1 Updated

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SAGE OF OSCILLOSCOPE

LOCATION = RESEARCH 1 EE LABS

2ND SEMESTER

DATE: 21ST FEBR ARY 2014

GRO P 5

CREATOR OF THIS LAB REPORT: ALEE KAZMI

GRO P MEMBERS: DORIN G CLIS , CLEMENCE JOMIMASSA

NSINDO

MAILBO N MBER !2


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INTRODUCTION TO THE EXPERIMENT

In these experiments we will try to identify and see the basic principles of the oscilloscope. These

experiments involve the charging and discharging of capacitors.

OSCILLOSCOPE

It is a device which displays signals in the form of voltage and time graphs which are then analysed

from the screen of the oscilloscope. They are calibrated and then adjusted so that voltage and the

time can be read directly from a screen connected in it. The experiments show us the methods of

analysing AC and DC signals on an oscilloscope. The simple oscilloscope can be divided into various

sections: The ertical control! The hori"ontal control! Trigger Controls and the display.

Vertical Control

Contains a sensitivity #nob$ AC%DC%&round selector and the ' vertical input plug.

Trigger Control

Contains the start of the x(axis sweep. This also contains the auto set button which automatically

resets the wave to its original state if its display settings have been altered too much.

Horizontal Input

This includes the timebase settings and the hori"ontal sensitivity switch. Another input for another

signal is also available for dual signals.

)scilloscope can be used for multiple tas#s such as *elative measurements$ +hase difference$

,re-uency measurement$ +ulse rise or fall measurements$ Time and voltage measurements.

astly the use of probes with an oscilloscope is very useful. It contains resistance of its own which

can be used to attenuate the signals since they act as a voltage divider. The attenuation can go up

to '/x. At the same time$ this helps to isolate the capacitive load presented by the probe0s cable.

The probe itself has a button on it to adjust the attenuation.

CAPACITOR

A capacitor is a device which stores electrical charge between two conducting plates in an

insulator. Capacitance or rather the capability of a capacitor to store charge is directly proportional

to the surface areas of the plates$ and is inversely proportional to the separation between the

plates. Capacitance also depends on the dielectric constant of the substance separating the plates.


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SINAL PROPERTIES

This picture very

accurately sums up

the components of an

AC signal. The average

value of this signal.

The amplitude is the

distance from the

max to the / point.

+eriod is the time

ta#en for the wave to

complete one cycle.

The fre-uency is the

number of cycles a

wave completes in

once second


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EXPERIMENT SETUP AND O!SERVATIONS

APPRATUS USED IN ALL THE EXPERIMENTS'1 Te#tronix )scilloscope

21 3labo

41 '/5ohm resistor

61 +ower supply

71 8ignal &enerator device connected in wor#bench

91 Capacitor '/n,

1 ;readboard%Connecting wires as s#eleton

PART " #$ SAGE OF THE "ERTICAL CONTROL

MAIN O!%ECTIVE

This is a basic experiment in which the use of the vertical control which include the position #nob

for Channel ' and Channel 2$ their menu$ sensitivity #nob


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e-ual to the one on the probe else the wave does not display correctly. astly the auto set button

is pressed which resets the display of the wave to its original state. 8ince the wave was

propagating$ the *un%8top button was pressed to halt it.

At this moment$ a hard copy of the screen was ta#en. It should be noted that the sensitivity wasautomatically set at './ per graticule division.

The position #nob in the hori"ontal section


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The value of the voltage can be calculated using the following formula(:Counte) Di*i+ion+ in c, - Scale .actor in V/)i*i+ion 0 Value in *oltage

&'&'& MEASURE VOLTAE USIN THE CURSORS

PROCEDURE CARRIED OUT

The auto set button was pushed to reset the wave to its original setting. @ow the cursor button is

pressed which opens a menu. The type of cursor is selected to voltage in order to measure the

voltage. Although it is unnecessary since we are wor#ing with only one channel source but

nevertheless the source was selected to Channel '. A hard copy was ta#en at this instance.

The values of the upper$ lower cursors$ delta and various minor settings are calculated in the

following table.

&'&'1 MEASURE VOLTAE USIN THE MEASURE .UNCTION

PROCEDURE CARRIED OUTImmediately before the previous experiment$ the auto set button was pressed and then the

measure button. =in$ =axB and +#(+#B mode were selected. A hard copy was ta#en at this

Range

V V V

1.00V 2.2 2.72 0.52 0.1V 00.5V 2.18 2.74 0.5 0.1V !"

Vmin Vmax Vpp Estimated Resolution V/[div] Ve#ti$al Divsions

V/[div]


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instant with the mode selected. ,or 7//m range(:

,or ' range(:

The pea# to pea# voltage is 9//m for both ranges.


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&'&'2 S3ITCHIN THE INPUT COUPLIN


There is a slight modification in this experiment as we are filtering out the DC part of the signal.

This is done by selecting the AC coupling in C?' menu. It should be noted that in case of small

fre-uency it affects out measurements.. The auto set button is not pressed and a sine centred

curve is seen. 8ince the signal was not stable$ the trigger was adjusted with the 33 #nob in the

trigger section.

Range/,V Voltage Pea4 to Pea4/V

'// /.62

&'&'5 Veri67 t8e ,ea+ure,ent+ 9it8 a ,ulti,eter


The oscilloscope probe is removed from the signal generator and the 3labo multimeter is set to DC

and connected to the signal generator. The ground pin of the 3labo is then connected to pin ' andthe


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PART : #$ SAGE OF THE HORIZONTAL CONTROL

MAIN O!%ECTIVE

This is a basic experiment in which the use of the hori"ontal control which include the hori"ontal

position #nob for Channel ' and Channel 2$ their menu and the sensitivity #nob


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A table will be compile at the end. The time between the rising edges of two consecutive

rectangular components was measured using cursors. Delta time is distance between the first and

second cursors to "ero so in our case$ the wanted value

To measure the fre-uency of the rectangular component$ the signal is adjusted to cover the entire

portion of the screen. The scale factor of the time base is also recorded.

The amplitude of the rectangular part is also obtained from here since the wave is big and accurate

enough to be counted and then multiplied by the volts per division.

The fre-uency of the sine component is measured by "ooming enough to scale one sine wave. A

cross point is then used between the signal and the grid as reference points for the cursors. The

pea# to pea# value is measured using hori"ontal cursors. astly$ the falling edge of the rectangular

component is used to measure the time distance of the sine from the beginning of the falling edge

of rectangular component.

,or the rectangular component(:

Cursor'


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,or the AC component(:

&'1'( Dela7e) an) e;pan)e) *ie9 o6 +ignal+


The auto set button is pressed and the wave position adjusted. After that$ the hori"ontal menu

button is pressed and the =ain is selected. ,rom the side screen menu$ 0window "one is selected.

Two additional vertical bro#en lines are visible on the screen. 0>indow0 is selected from the side

screen menu and the selected region "ooms in. This is done because the wave is -uite small to be

measured accurately. Fsing the position #nob from the hori"ontal section$ the position of the wave

is adjusted till a little more then one period of the wave covers the graph. A hard copy is ta#en and

properties of the signals recorded.

PART ( #$TRIGGER SECTION

INTRODUCTION TO THE !ASICS

This is a basic experiment in which the use of the trigger which include$ the control set for theamplitude level$ trigger menu$ set level to 7/G$ force trigger$ trigger view and input ext trigger$ is

emphasi"ed and practised on. >e will perform a series of experiments focusing on specific groups

)#e*uen$+ o& t'e sine signal %u#so#1 %u#so#2 Delta,%u#so#- &&set om t'e g#ound ime distan$e o& sine"4.4 504mV 2.2V 2.7"V 0.7"V 2.4V 10.5ms 47.0

Vpp value o& sine $omponent 42mV p3!p3


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of the hori"ontal section.

The trigger menu contains a type$ source$ slope$ mode and coupling mode.

&'2'( U+ing t8e


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Trigger Po+ition/,+ Trigger Le*el/V Slope

='==,+ "'>2V Ri+ing

@ow the trigger is shifted slowly from (' to 9. At about /.6(6.$ the signal behaves strangely

and starts moving bac# and forth. At about 6.$ the signal moves correctly again. The vertical

resolution is changed to 7//m%Div and the trigger varied slowly between 2 and 4. At about 2.7

$ the graph moves bac# and forth. After this at about 2.$ it moves to the left no change can be

further detected in it. A hard copy is ta#en. The only difference to the previous image is obviously

that the slope is falling now and the graph shifter to the left.


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&'2'& Ot8er i,portant trigger control+


The probe is connection to pin 6 of the signal generator. The coupling is set to AC$DC and ground

coupling which show the AC$ DC and ground part of the wave respectively.At AC coupling$ the

wave is centred. )n DC$ it displays a triangular wave form and on ground there is / signal$ off

course.

The coupling is set to DC and probe connected to pin 9 of the signal generator. The auto set button

is pressed and a stationary signal is seen. After setting the trigger to (4$ the signal starts to move.

The probe tip is disconnected for pin 9 and the mode set to normal. The probe tip is again

connected bac# to pin 9 of the generator. There is no signal now. The trigger is adjusted and the

same signal returns.

PART & #$ SING THE PROBE

I

NTROD CTION TO THE BASICS

The use of probes and their implementation is discussed in this section. >e shall be using passive

probes with ':' and '/:' attenuation. The other #inds such as active probes and differential

probes are not used. The following is the schematic of a probe(:

The probe acts li#e a low pass filter.


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The probe is connected to pin 9 on the signal generator and the attenuation set to 'x. The probe

factor on the oscilloscope is also set to 'x. The coupling is set to DC and the auto set button

pressed. The time base is altered from the hori"ontal menu so that only one period is visible on thescreen. The vertical resolution is set to the highest possible range.

&'5': Pro


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The variable capacitor is turned a further / degrees in cloc#wise direction. ?ori"ontal and vertical

scale is adjusted again and a hard copy ta#en(:

.re?uenc7/MHz Vpp/V

'2./2 .'2


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&'5': Pro


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Pea4 to Pea4/V .re?uenc7/MHz

7.// '2./7

PART & #$ DISCHARGING THE CAPACITOR

PROCED RE CARRIED O T

The following circuit is build up from a breadboard.

The attenuation is set to '/x on the probe and the vertical menu. Trigger is set to normal mode$

falling edge. The supply is turned on and the capacitor charges in a few seconds. As soon as the

oscilloscope showed '/$ the supply cable was pulled out of the power source and resultantly the

capacitor started to discharge. The process is repeated a couple of time in order to adjust the time

base. The trigger mode is not set to 0single0 and the curve is adjusted so that it spreads over the

entire screen. A hard copy is ta#en(:


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Trigger

Po+ition/,+

Re+olution

/V

Mo)e Coupling Horizont

al Scale@+.actor/u

+

Trigger Le*el/V Slope

2./E/ 2.// @ormal 8ingle 7// ./6 ,alling

EVALUATION

"B

IHm posting the table from the first experiment again.

oltage oltage per divisionsJ@umber of divisions

,or './/%div sensitivity(:

min ' J 2.2 2.2

max 'J2. 2.

Range V delta Estimated ResolutionV

1.00V 2.2 2.7 0.5 0.1V

0.5V 1.4 2.4 1 0.1V

Vmin VmaxV/[div] Div Div V/[div]


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,or /.7%div sensitivity(:

min /.7 J '.6 /.

max /.7J 2.6 '.2

dc


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Accurac7 o6 o+cillo+cope 6or *ertical po+ition at non#zero#$

,or *ange of 2m%div to 2//m%div(:

e could ta#e the wrong reference point while ta#ing some readings or wrongly measure while

ta#ing the readings. =oreover$ "ero error in oscilloscope can also be an issue. astly$ there is a

probability of damaged probes.

Met8o) : Cur+or+B#$

The "ero error and damaged probes still apply. >e can ta#e wrongs reference points by not

properly


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Met8o) &U+ing ,ulti,eterB

Internal resistance of multimeter or "ero error in multimeter can account for error.

Fsing a higher resolution would mean mathematically a lower resolution number. This would in

turn decrease the amount of relative error after the formula has been applied. ?ence$ it is better

to use higher resolutions.

AC coupling affects the display of small fre-uencies and may filter small AC fre-uencies out too.

As observed from the calculations above$ the multimeter should be preferred over then

oscilloscope due to its much lower relative error of /.''G as compared to 4.EG.

:B

Error +ource+ 98ile ,ea+uring 6re?uenc7

ets consider the case of cursors. There could be a device error$ an error while aligning the cursors

or maybe a probe error. There is also an error as fre-uency is measured with a delay and an

expanded view. There might also be a device error$ error in the resolution$ effect of the probe or

the "ero error in the oscilloscope.

Accurac7 o6 t8e o+cillo+cope in *ariou+ ,o)e+#$

In single shot and sample mode:

K(


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able to thus put the cursors very accurately at appropriate areas. This further reduces the

possibility to use a wrong "ero value.

91 >e should use the oscilloscope to measure time and fre-uency because not only is the reading

more user friendly to understand but the accuracy can be increased by following specific steps

such as using the window mode of oscilloscope and increase the resolution and fit the entire

image on the screen as much as possible.

(B

Trigger Po+ition 0 It is the position on the hori"ontal scale of the waveform where trigger occurs.

Trigger Le*el 0 It is theinstantaneous level that a trigger source signal must reach before a sweep

is initiated by the trigger circuit.

Slope 0 =ore commonly #nown as the gradient. It is used to give the nature of a wave.

@ow the trigger is shifted slowly from (' to 9. At about /.6(6.$ the signal behaves strangely

and starts moving bac# and forth. At about 6.$ the signal moves correctly again. The only reason

for this can be either because it changed between the triggered and non(triggered option ormaybe the varying amplitude in the signal.

At the following$ we can see the arrow is at the rising edge.


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At the following the arrow is pointing to a falling slope.

The differences between auto and normal mode(:

,irst of all$ the trigger level to stabili"e the signal is different in both of the modes. In the normal

mode$ the signal stops to be displayed if the signal drops to a low level whereas in auto mode$ it is

still present. @ormal mode is very easy to handle since the signal gets triggered as the trigger

enters a certain range but there is no signal if it is not triggered. Concluding$ in normal mode one

has to vary the trigger himself at each reading but in auto mode$ the oscilloscope does it for us.

&B

Pro


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At 'x(:

N


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41 FF


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('///('%Constant

Time Constant '%'///

Time Constant /.//'

71 In my opinion$ its best to get the time constant from the graph since the errors in the curve

average out when we ta#en the gradient. If we ta#e it directly from the oscilloscope it presents us

with an unreliable value since ta#ing the exact gradient of a curve at a certain point is difficult and

very error prone without the e-uation of the curve. >e could also of course directly calculate the

time constant as done in the part ' of this series0 evaluation but the tolerance of the capacitor and

the resistor affects the value.

CONCLUSION

The C*) is a device which can display a waveform and give new

perspective to it thereby increasing the scope of the

interpretation of a wave. It can be seen that using the cursors and

the measure function are much more accurate then using the

method of graticule divisions. 8econdly$ we should ta#e maximum

advantage of the units%div switch or sensitivity switch since it

allows a larger wave form which further allows more accurate

cursor placement on curves and more accurate readings.

Triggers are very useful for measuring the -uality of a signal orrather specific parts of the signal. ?owever they need to be

adjusted for different waves and modes. Care should be ta#en as

to use an appropriate form of mode.

+robes allow for greater accuracy since they compensate the

capacitance in the wires. A 'x probe is best for lower fre-uencies

and '/x for higher fre-uencies. +robes must be calibrated before

an experiment else they might produce errors and theattenuation be according to the magnitude of the fre-uency else


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there might be a significant error.

The last experiment involved calculating the time constant of a

capacitor most accurately by 4 ways but the logarithmic scale oneproved to be the most accurate since it cancels out the systematic

error. ,urthermore$ the curve on the oscilloscope is blurred and

not that accurate to draw a tangent on. The tolerance of the

resistor and capacitor add error to the direct formula method.

Therefore I concluded on this base that the logarithmic scale

method is the best.

RE.ERENCES

'1 Capacitor +icture

http:%%www.tvrepair#its.com%xcart%images%+%aluminumOelectrolyticOcapacitor.jpg

21 >ave Components &raph

http:%%www.electronics(tutorials.ws%accircuits%AC(waveform.html

41 ab =anual

61 )scilloscope

Documents

Lab Report 1 Updated