Instruction Manual (PDF)




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Title: petree3153-1002
Author: Wes Petree

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Introduction*to*Electrical*
Engineering*Equipment*
Power*Supply*and*Digital*Multimeter*
Wes$Petree$

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Experiment$description:$

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This!experiment!is!designed!to!introduce!students!who!are!early!in!their!curriculum!
to!the!equipment!that!will!be!utilized!in!the!circuits!and!electronics!laboratories.!It!
will!help!to!familiarize!the!students!to!the!power!supplies!used!to!power!their!
circuit!designs!and!the!multimeters!they!will!use!for!trouble!shooting!those!designs!
when!they!are!not!working!as!intended.!Additionally,!it!will!help!to!verify!what!the!
students!have!learned!in!their!circuit!theory!classes.!
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Students!will!construct!a!simple!resistive!circuit!and!measure!the!various!voltages!
and!the!current!through!the!circuit.!The!multimeter!is!the!primary!tool!for!
conducting!this!type!of!analysis!of!DC!circuits.!AC!circuit!analysis!will!be!conducted!
in!later!experiments!and!will!introduce!the!oscilloscope!as!the!primary!tool!for!
conducting!such!analysis.!The!multimeter!is!helpful!in!troubleshooting!the!AC!
circuits!and!will!be!used!in!those!circuits!as!well,!and!therefore!a!strong!
understanding!of!it!is!needed!before!leading!into!AC!circuit!analysis.!

Caution:$
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It!goes!without!saying!that!it!is!necessary!to!be!cautious!when!dealing!with!
electricity.!However,!the!voltages!and!currents!the!power!supplies!in!the!lab!
do!not!produce!enough!current!to!cause!any!bodily!harm.!However,!wall!
power,!which!is!not!used!in!this!experiment,!can!exceed!the!amount!of!
current!necessary!to!cause!bodily!harm.!Take!caution,!as!with!any!appliance,!
when!plugging!into!wall!power!if!the!equipment!is!not!already.!

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Safety$Instructions:$
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Use!caution!when!dealing!with!small!electronic!components.!Component!
legs!and!IC!pins!can!poke!you!and!draw!blood!if!caution!is!not!observed.!IC!
pullers!are!recommended!when!using!ICs!on!breadboards.!

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Necessary$Equipment:$
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Hewlett!Packard!E3620A!0K25V,!0K1A!!
Dual!Output!Power!Supply!

Figure$1:$Power$Supply$

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Fluke!45!Dual!Display!Multimeter!
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Figure$2:$Digital$Multimeter$

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Solderless!breadboard!
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NOTE:!there!are!positive!and!negative!rails!
located!on!both!the!top!and!the!bottom!in!the!
picture!to!the!right.!They!run!the!length!of!the!
breadboard!and!are!connected!by!a!
conductor,!making!every!point!on!each!
respective!rail!have!the!same!voltage!
potential.!Likewise,!the!holes!running!on!the!
inside!of!the!breadboard!are!connected!
perpendicularly!to!the!direction!of!the!
positive!and!negative!rails.!These!are!all!
numbered!and!each!contains!5!holes!that!
share!a!connection!on!the!bottom!side!of!the!
board.!

Figure$3:$Solderless$Breadboard$

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Resistors:!1K470Ω,!1K220Ω!
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Resistors!are!found!in!the!bin!along!the!NW!
wall!of!the!lab.!

Figure$4:$Resistors$

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Resistor!color!codes!give!a!way!of!marking!the!
resistance!values.!The!gold!band!means!that!
the!value!is!within!±5%!of!the!marked!value.!
The!value!is!read!as!the!2!furthest!most!colors!
from!the!tolerance!band!being!the!2!most!
significant!digits!and!the!third!being!a!power!
of!10!multiplier!of!the!first!2!numbers.!The!
example!on!the!right!shows!yellow!=!4,!purple!
=!7,!and!orange!=!103.!Therefore,!the!
resistance!value!is!47!×!10! ,!which!is!47000Ω!
or!47kΩ.!
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Resistor!color!codes!are!also!found!in!the!lab.!

Figure$5:$Resistor$Color$Code$

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NOTE:!All!items!located!in!Advanced!Electronics!Laboratory!(CEC!203)!

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Definitions$and$Background$Preparation:$

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Circuit!–!a!complete!and!closed!path!around!which!a!circulating!electric!current!can!flow.!
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Voltage!–!a!differential!measurement!of!the!electric!potential!to!move!charged!particles!
from!one!point!to!the!other!point!that!is!being!measured!and!is!measured!in!Volts!(V).!
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Current!–!the!flow!of!charged!particles!through!a!conducting!material.!It!is!measured!in!
Amperes!or!Amps!(A).!!
Current!is!usually!labeled!I.!The!convention!for!current!flow!is!the!direction!that!
positively!charged!particles!would!flow!within!a!given!electric!field,!or!simply!put!
from!a!higher!potential!node!to!a!lower!potential!node!if!the!circuit!element!the!
current!is!flowing!through!is!a!passive!element!–!that!is!it!does!not!provide!power!to!
the!circuit,!it!dissipates!power!from!the!circuit.!A!common!analogy!is!to!think!of!the!
current!as!water!and!potential!to!be!the!same!type!of!potential!that!gravity!is!in!
regards!to!height!away!from!the!earth’s!center!of!gravity.!Looking!at!Figure!6,!Node!
2!is!at!a!higher!potential!than!Node!3!with!respect!to!R1,!so!the!current!flowing!
through!R1!is!in!that!direction!(from!left!to!right)!and!is!labeled!with!an!arrow!and!I.!
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Node!–!any!point!in!a!circuit!that!connects!2!or!more!circuit!elements.!!
The!voltage!along!any!node!is!same!anywhere!along!that!node.!That!means!that!if!a!
wire!is!connecting!2!elements,!anywhere!on!that!wire,!the!voltage!potential!is!the!
same.!
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Passive!element!–!any!circuit!element!that!does!not!provide!power!to!the!circuit.!!
The!resistors!in!this!case!are!the!passive!elements!and!are!labeled!R1!and!R2.!
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The!nodes!have!been!labeled!and!the!
current!direction!shown.!!
Note:!the!+!and!–!signs!indicate!relative!
potential!felt!by!each!circuit!element.!

Figure$6:$Schematic$of$simple$resistive$circuit$

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Ohm’s!Law!states!that!there!is!a!directly!proportional!relationship!between!the!voltage!and!
the!current!in!a!circuit!with!the!resistance!being!the!constant!of!proportionality.!
! = ! ∙ !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"#$%&'(!1!
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Kirchhoff’s!Voltage!Law!(KVL)!states!that!the!voltages!summed!around!a!closed!loop!equals!
zero.!The!sum!of!all!the!voltage!drops!equals!the!sum!of!the!voltages!supplying!power!to!
the!circuit.!
Voltage!supplied = Node!1!V + Node!2!V + Node!3!V!
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Notice!that!Node!1!is!the!reference!node.!That!means!that!the!voltage!at!that!node!is!zero!
and!is!tied!directly!to!ground.!This!simplifies!our!KVL!to!just!the!sum!of!the!voltage!drops!
across!the!2!resistors.!
12V = V!! + V!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"#$%&'(!2!
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Equivalent!resistance!is!the!combination!of!all!resistances!in!a!given!circuit.!There!are!
series!combinations,!parallel!combinations,!and!combinations!of!serial!and!parallel.!This!
experiment!deals!solely!with!series!resistances,!which!can!be!calculated!simply!by!the!
algebraic!sum!of!all!the!resistors!in!series.!
!!" = ! !! + !! + !! + ⋯ + !! !!!!!!"#$%&'(!3!
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Theoretical$Calculations:$
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1. Use!equation!3!to!determine!the!equivalent!resistance!of!the!circuit!in!figure!6,!!
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R1,=,220,Ω,and,R2,=,470,Ω.,Therefore,,Req,=,220,Ω,+,470,Ω,=,690,Ω.!!
2. Use!the!calculated!resistance!value!from!step!1!in!equation!1,!Ohm’s!Law,!to!
determine!the!theoretical!current!in!the!circuit.!!
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Solving,for,I,,the,equation,becomes,! = !/!.,The,Voltage,supplied,to,the,circuit,is,
known,and,the,Resistance,has,been,calculated,,so,the,only,unknown,is,the,current,,I.,
Inputting,values,of,12,V,and,690,Ω,yields,the,theoretical,current,value,of,0.0174,A,or,
17.4,mA.!
3. Use!the!calculated!current!and!the!value!of!R1!in!equation!1,!Ohm’s!Law,!to!
determine!the!voltage!drop!across!R1.!
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! = ! ∙ !! = !0.0174!A ∙ 220!Ω = 3.83!V!
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Repeat!with!R2,!using!the!same!current!value.!
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! = ! ∙ !! = !0.0174!A ∙ 470!Ω = 8.17!V!
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4. Add!the!results!of!step!3.!Does!this!confirm!KVL!–!is!equation!2!satisfied?!

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V!! + V!! = 3.83!V + 8.17!V = 12!V✔
Yes,,KVL,is,confirmed.,12,V,is,what,was,supplied,to,the,circuit,and,is,equal,to,the,sum,
of,the,voltage,drops,in,the,circuit.,,
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Take$Measurements:$
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1. Turn!on!the!power!supply!and!make!
sure!display!is!showing!V1!by!
pressing!the!button!directly!under!the!
display!that!corresponds!to!V1.!Also!
connect!the!red!and!black!probes!into!
the!corresponding!red!and!black!
ports!on!the!V1!output!on!the!front!of!
the!power!supply.!

Figure$7:$Probes$used$for$connecting$the$power$supply$
and$the$multimeter$to$the$circuit$

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2. Turn!the!knob!for!V1!until!it!shows!
12.00!or!as!close!as!you!can!get.!It!is!
sometimes!hard!to!get!exactly!12.00!
and!the!knobs!can!be!very!touchy.!As!
long!as!the!voltage!is!within!±!0.02V!it!
should!be!fine.!The!voltage!will!be!
fineKtuned!in!a!subsequent!step;!so!
don’t!get!too!hung!up!here.!!

Figure$8:$Power$supply$showing$12.00$V$

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3. Connect!the!red!probe!from!the!
power!supply!to!one!of!the!positive!
(+)!rails!on!the!breadboard!and!the!
black!probe!to!one!of!the!negative!(K)!
rails!(preferably!on!the!same!side!as!
the!+!rail!that!was!just!connected!–!
this!will!make!the!circuit!easier!to!
build).!

Figure$9:$$Connect$power$to$the$circuit$with$the$probes$

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4. Turn!on!the!multimeter!and!connect!
the!red!and!black!probes!into!the!far!
left!vertical!ports.!The!red!is!labeled!
for!voltage!and!resistance!measuring.!
The!black!is!labeled!COM,!which!
stands!for!common!–!another!term!
used!for!reference!or!simply!ground.!
However,!one!should!note!that!it!is!
not!grounded!to!earth,!but!rather!
simply!gives!the!multimeter!a!
reference!to!determine!the!
differential!between!the!2!probes.!
Figure$10:$The$2$most$left$ports$are$for$Voltage$and$
Resistance$measurements$

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5. Press!the!V!for!voltage!button,!located!directly!under!the!display,!to!ensure!that!the!
multimeter!is!in!voltage!mode.!
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6. Connect!the!probes!of!the!multimeter!
to!the!rails!of!the!breadboard!as!in!
step!3.!This!will!allow!the!multimeter!
to!display!the!voltage!of!the!
breadboard!rails.!
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Figure$11:$Multimeter$reading$12.070$V$instead$of$the$
12.00$V$the$power$supply$displayed$

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7. Calibrate!the!power!supply!by!
adjusting!the!power!supply!so!that!
the!multimeter!reads!as!close!to!12!
volts!as!possible.!
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Figure$12:$Adjust$the$power$supply$until$the$multimeter$is$
as$closed$to$12V$as$possible.$$

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It’s!hard!to!see,!but!the!voltage!
reading!on!the!power!supply!was!
11.93!after!calibrating!to!the!
multimeter.!

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Figure$13:$Power$supply$reading$11.93$V$after$calibration$

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8. Now,!construct!the!circuit!that!is!shown!by!the!schematic!of!figure!6.!Place!one!leg!of!the!
220Ω!resistor!into!the!(+)!rail!and!the!other!leg!into!one!of!the!inner!holes!on!the!board.!
Now,!place!one!leg!of!the!470Ω!resistor!in!one!of!the!holes!immediately!adjacent!to!the!hole!
on!the!inner!board!used!for!the!220Ω!resistor,!making!sure!it!is!the!same!numbered!hole,!
and!the!other!leg!into!the!(K)!rail.!
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9. After!the!circuit!is!constructed,!place!
the!multimeter!probes!on!either!side!
of!each!resistor!and!record!the!
voltage!from!the!display!of!the!
multimeter.!
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NOTE:!Make!sure!that!the!red!(+)!
probe!is!on!the!same!side!that!the!
schematic!shows!to!be!+!in!respect!to!
that!resistor.!Otherwise,!it!will!show!
the!same!magnitude,!but!with!
opposite!sign!–!i.e.!it!will!show!the!
voltage!as!negative.!
Figure$14:$Connect$the$multimeter$probes$across$R1$and$
then$repeat$for$R2$

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!!!!!!!!!!!!!

Figure$15:$Voltage$reading$across$R1$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$Figure$16:$Voltage$reading$across$R2!

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10. Pull!the!probes!out!of!the!multimeter!
and!replace!them!in!the!current!
measuring!position.!The!black!probe!
will!go!into!the!same!COM!port!and!
the!red!will!now!go!into!the!port!
directly!to!the!right!(horizontal)!from!
it.!
Also,!make!sure!to!press!the!A!button!
for!measuring!current.!
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Figure$15:$Replace$the$probes$into$the$current$measuring$
position$

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11. Break!the!circuit!by!pulling!any!of!the!
resistor!legs!out!of!the!hole!on!the!
breadboard.!
This!stops!current!from!flowing!
through!the!circuit.!By!connecting!the!
multimeter,!current!will!flow!through!
the!multimeter!and!allow!it!to!
measure!and!display!the!amount!of!
current!going!through!it.!
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Figure$16:$Break$the$circuit$

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12. Connect!the!multimeter!probes!to!the!
circuit.!Be!sure!to!connect!the!red!to!
the!+!side!of!the!broken!node!and!
complete!the!circuit!by!connecting!the!
black!probe!to!the!other!side.!
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Imagine!that!the!multimeter!is!just!a!
wire!that!is!reconnecting!the!broken!
circuit.!However,!it!is!important!to!
make!sure!that!the!probes!are!placed!
in!the!correct!polarity:!red!for!+!and!
black!for!–.!If!they!are!connected!in!
the!wrong!polarity,!the!magnitude!
will!be!correct,!but!the!direction!of!
Figure$17:$Complete$the$circuit$with$the$probes$of$the$
current!flow!will!be!opposite!the!
multimeter$
correct!direction!–!i.e.!negative!
instead!of!positive!(the!sign!only!
!
indicates!the!direction)!
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13. Record!the!measurement!and!note!
the!relation!to!the!theoretical!value!
that!was!calculated.!

Figure$18:$Record$the$current$measurement$

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Compare!the!theoretical!values!with!the!measured!values.!
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Theoretical$Values$Calculated$

Measured$Values$

VR1$
3.83,V!
3.864,V!
VR2$
8.17,V!
8.138,V!
VR1$+$VR2$
12.0,V,
12.002,V,
I$
17.4,mA!
17.773,mA!
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The,theoretical,value,were,VR1,=,3.83,V,,VR2,=,8.17V,,and,I,=,17.4,mA.,The,calculate,values,were,VR1,=,
3.864,V,,VR2,=,8.138,V,,and,I,=,17.773,mA.,These,values,are,very,close,to,the,expected,values.,The,
variance,can,be,explained,by,the,5%,tolerance,of,the,resistances,as,well,as,the,voltage,at,the,rails,
showing,12.002,V.,Adding,VR1,and,VR2,together,results,in,12.002,and,therefore,confirms,the,KVL.,
Multiplying,the,current,of,17.773,mA,by,the,resistances,R1,and,then,R2,results,in,VR1,=,3.9,and,VR2,=,
8.35,V,,thereby,showing,Ohm’s,Law,valid,as,well.,

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