University of Houston
College of Technology
Computer Engineering Technology and Electrical Power
Technology
Freshman Laboratory
ELET 1400
Experiment 1
Equipment Use, Basic Concepts of DC Voltage and Current, Resistor, and
Capacitor
© – 2014 University of Houston, College of Technology ELET Labs
Table of Contents
1
Purpose ...................................................................................................................... 4
2
Objectives ................................................................................................................ 4
3
Equipment and Components .................................................................................. 4
4
Pre-Lab ...................................................................................................................... 5
5
Laboratory procedures .......................................................................................... 5
5.1
Procedure 1 – Familiarity with the Digital Multi-meter .......................... 5
5.2
Procedure 2 – Resistors and Resistance ..................................................... 7
5.2.1
Finding the resistor nominal value: Color-Code Practice. ................ 9
5.2.2
The measured value of a resistor ....................................................... 11
5.3
Procedure 3 – Capacitance ........................................................................... 11
5.3.1
Ceramic capacitors ................................................................................. 13
5.3.2
Electrolytic capacitors .......................................................................... 16
5.3.3
Capacitance Measurements .................................................................. 16
5.3.4
Finding capacitor nominal value ........................................................... 17
5.3.5
The measured value of the capacitors .............................................. 17
5.4
Procedure 4 – The Power Supply ................................................................ 18
5.4.1
Controls and Indicators ........................................................................ 19
5.4.2
How to set and display voltage ............................................................ 21
5.5
Procedure 5 – The DC Power Supply and the Multi-meter................... 21
5.5.1
5.6
Voltage Adjustments: ............................................................................ 21
Procedure 6 – Soldering and Desoldering Techniques .......................... 23
5.6.1
Soldering Practice .................................................................................. 23
5.6.2
Desoldering .............................................................................................. 25
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5.7
Procedure 7 – Measuring Voltage and Current ....................................... 25
5.7.1
Measuring voltage drop across a resistor: ....................................... 26
5.7.2
Measuring current flow through a resistor...................................... 26
6
Knowledge Evaluation: .......................................................................................... 28
7
References: ............................................................................................................ 28
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1 Purpose
This experiment provides an introduction to the equipment that will be used
in this lab such as the digital multi-meter (DMM) and the dc power supply. In
addition, two basic components will be introduced in this experiment: the
resistor and the capacitor. The purpose of this experiment is to obtain the
nominal and measured values of these components. Finally, the basic
soldering of components to the proto-boards and construction of the first
circuit will be performed.
2 Objectives
At the end of this experiment you will know:
1. The features available in a DMM: how to use a DMM to measure
voltage, current, resistance, and capacitance.
2. How to read resistance using the resistor color code and how to
determine the nominal resistance value and measure resistance
using the DMM.
3. How to read the nominal value of a capacitor and measure its
capacitance using the capacitance feature of the DMM.
4. The features available in a DC power supply: how to use a DC power
supply to supply DC voltage/current to a circuit.
5. The basic soldering and desoldering techniques on a proto-board.
3 Equipment and Components

Digital Multi-meter (DMM)

Power Supply
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
Soldering Gun/Solder

Printed Circuit Board (PCB)

Resistors: 4.7 Ω, 6.8 Ω, 220 Ω, 1 KΩ, 1 M Ω

Capacitors: 0.1nF, 10nF, 2.2nF, 22nF, 33nF.
4 Pre-Lab
You do not have pre-lab assignment for this experiment.
You will have a Quiz base on this manual before the lab.
5 Laboratory procedures
5.1 Procedure 1 – Familiarity with the Digital Multi-meter
In this procedure, you will familiarize yourself with
the controls and indicators of the Digital Multi-Meter.
The DMM is a highly versatile instrument which offers portability as well as
precision. A DMM includes the following functions:

AC and DC current and voltage measurements

Resistance and capacitance measurements

Diode test

Continuity test
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Figure 1. The B+K Precision Bench Type 3-1/2 Digit Multimeter
Controls and Indicators: These controls and indicators are important in the
measurements of voltage, current, resistance, and capacitance.
Refer to
Figure 1 in this procedure to identify the controls and indicators listed
below.
1.
Power Button.
2. 20 Ampere Jack: Input for 20 amp DC/AC current range.
3. V Ω Jack: Input Jack for voltage measurements, resistance
measurement, diode testing, and continuity testing.
4. DC/AC Switch: selects DC/AC in voltage and current functions.
5. Display panel.
6. CX (+) Jack: Positive input for capacitance measurements.
7. CX (-) Jack: Negative input for capacitance measurements.
8. 20 A/20 MΩ/20 μF push button switches: Selects 20-ampere range
for DC and AC current functions, 20 MΩ for resistance function, and
20 μF for capacitance function.
9. 1000 V/2000 mA/2000 kΩ/ 2000 nF Switch: Selects 1000 V range
for DC and AC voltage functions, 2000 mA for DC and AC current
functions, 2000 kΩ for resistance function, and 2000 nF for
capacitance function.
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10. 200 V/200 mA/200 kΩ/ 200 nF Switch: Selects 200 V range for DC
and AC voltage functions, 200 mA for DC and AC current functions,
200 kΩ for resistance function, and 200 nF for capacitance function.
11. 20 V/20 mA/20 kΩ/ 20 nF Switch: Selects 20 V range for DC and
AC voltage functions, 20 mA for DC and AC current functions, 20 kΩ
for resistance function, and 20 nF for capacitance function.
12. 2 V/2 mA/2 kΩ/ 2 nF Switch: Selects 2 V range for DC and AC
voltage functions, 2 mA for DC and AC current functions, 2 kΩ for
resistance function, and 2 nF for capacitance function.
13. 200 mV/200 μA/200 Ω Switch: Selects 200 mV range for DC and AC
voltage functions, 200 μA for DC and AC current functions, and 200
kΩ for resistance function.
14. CX Switch: Selects capacitance function.
15. Ω (ohms) Switch: Selects resistance function.
16. A (ampere) Switch: Selects current function.
17. V (volts) Switch: Selects voltage function.
18. COMmon jack: Input for common test lead for all measurements
except capacitance.
19. A (ampere) Jack: Input for 200 μA to 2 A DC or AC current ranges.
5.2 Procedure 2 – Resistors and Resistance
In this procedure, you will learn:
How to read the resistance value of a resistor from its color code,
How to measure this resistance using the DMM, and
How to calculate its resistance tolerance range.
A resistor is a component that opposes current flow by introducing a certain
value of Resistance. This opposition to the current flow is accompanied by
dissipation of heat. A resistor is symbolized in diagrams with a zigzag line as
shown in Figure 2.
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R
Figure 2. Symbol of a Resistor
Resistors are probably the most common and well-known of all electrical
components. They can be used in many different applications:








They are used to drop voltage,
Limit current,
Attenuate signals,
Signal conditioning,
Act as heaters,
Act as fuses,
Furnish electrical loads and
Divide voltages.
There are numerous varieties of resistors. Appendix C shows some of the
most popular types of resistors.
The resistors have color-codes which indicate their resistances in ohms. The
procedure for determining the resistance of a color-coded resistor is based
on the method outlined in Table 1. Table 1 is a list of numerical values
associated with each color. The numerical value associated with a 220 Ω
resistor is presented in Figure 3.
Figure 3. Resistor color code example
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The first two bands (those closest to the left end of the resistor in Figure
3) determine the first two digits of the resistor value, while the third band
determines the power of 10 for the multiplier (namely, the multiplier is the
number of zeros to follow the first two digits). If the third band is silver
(0.05) or gold (0.1), it is a multiplying factor that establishes resistor values
less than 10 Ω. The fourth band is the percent tolerance for the chosen
resistor. The range of resistance values in Figure 3 are:
220 Ω ± 10% = 220 Ω ± 22 Ω then the range is 198 Ω to 242 Ω
Several examples of resistor values and their corresponding color codes are
shown in Table 1.
Nominal
Percent
Value
Tolerance
22 000 Ω
BAND
± 20%
1
2
3
Red
Red
Orange
No band
Tolerance
Range
± 4400 Ω
17600- 26400 Ω
4
100 Ω
± 5%
Brown
Black
Brown
Gold
±5Ω
95- 105 Ω
10 Ω
± 10%
Brown
Black
Black
Silver
± 1Ω
9- 11 Ω
1.2 K Ω
± 5%
Brown
Red
Red
Gold
± 60 Ω
1140- 1260 Ω
6.8 M Ω
± 20%
Blue
Gray
Green
No band
± 1.36M Ω
5.44- 8.16M Ω
Table 1. Examples of resistor color codes
5.2.1 Finding the resistor nominal value: Color-Code Practice.
1. Using the procedure described, determine the color bands for each
resistor in Table 2, find them in your lab kit and record the colors in
columns 1, 2, 3, and 4 in Table 2 in your worksheet.
COLOR BANDS
COLOR BANDS
Color
Numerical Value
Nominal
Value
4.7 Ω
220 Ω
1
2
Yellow Violet
Red
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Red
3
4
Black
Gold
Brown
Gold
1
2
3
4
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10 KΩ Brown Black Orange Gold
1 M Ω Brown Black
6.8 Ω
Blue
Gray
Green
Gold
Gold
Gold
Table 2. Resistor color code practice
2. Record the numerical value of each color in the next column, following
the example.
3. Sometimes the measured value of a resistance is different from the
value stated in the color code. The manufacturer builds the
resistances with different grades of accuracy. The more accurate
(lower tolerance) the higher the cost. The percent of tolerance is
used to determine the range of resistance values within which the
manufacturer guarantees the resistor will fall. This is determined by
first taking the percentage of tolerance and multiplying it by the
nominal resistance level. For instance
(5%)(22Ω)=(0.05)(22Ω)= 1.1 Ω
is added to and subtracted from the nominal value of 22 Ω to
determine the range as follows:
Maximum value = 22Ω + 1.1Ω = 23.1Ω
Minimum value = 22Ω - 1.1Ω = 20.9Ω
Compute and record the range of resistor values in Table 3 in your
worksheet.
Resistor
4.7 Ω
220 Ω
1 KΩ
1 M Ω
6.8 Ω
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Minimum Value
Maximum Value
4.465 Ω
4.935 Ω
10-30
Table 3. Resistor maximum and minimum values
5.2.2 The measured value of a resistor
1. Read the resistance value using the DMM. Following the instructions
stated earlier about the usage of a DMM, record your measured value
on the first column in Table 4 in your worksheet. Choose the correct
scale that will provide the highest degree of accuracy for the
measurement.
2. Determine the magnitude of the difference between the nominal and
measured values using the equation
% Difference 
Nominal  Measured
 100%
Nominal
and record the result in Table 4 in your worksheet.
Normal
Resistor
Value
4.7 Ω
220 Ω
1 KΩ
1MΩ
6.8 Ω
Measured
Value
Falls within
Specified
%
Tolerance(Yes/No) Difference
4.80 Ω
YES
2.12%
Table 4. Comparison between measured and calculated resistance
5.3 Procedure 3 – Capacitance
In this procedure, you will learn how to:
measure capacitance values, and find nominal capacitance.
Capacitance is the ability of a circuit or a device to store electrical charge.
The component specifically designed to have this capacity or capacitance is
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called a capacitor. The capacitor, similar to the resistor, is a passive
component in a circuit. The main feature of a passive component is absorbing
energy from the circuit. Capacitor is symbolized in diagrams with two plates
(one curve and the other straight) and the capacitance value is measured in
farads (F). Figure 4 shows the electrical symbol for a capacitor.
Figure 4. Capacitor symbol and nomenclature
The capacitor values vary from 1 Pico Farad (10-12 Farads) to Farads (in
electrolytic capacitors). It is very common to find the engineering notation
prefix in the capacitance values as shown in Table 5.
Name
Fraction
Times the unit
Engineering
notation
Mili
1/1,000
Micro
1/1,000,000
Nano
1/1,000,000,000
Pico
1/1,000,000,000,000
0.001
0.000 001
0.000 000 001
0.000 000 000 001
1x10-3 (mF)
1x10-6 (uF or F)
10-9 (nF)
1x10-12 (pF)
Table 5. Capacitor range of values
The capacitors have a variety of shapes, sizes, types, and applications and
can be either fixed or variable. The capacitor component has two conducting
plates and a dielectric in between as shown in Figure 5. The capacitors are
generally classified by the dielectric material used between the plates.
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dielectric
conductor
plates
Figure 5. Parts of a Capacitor.
They can be used in many different applications:







Electrical storage (low power circuits)
Power Supply filtering
Blocking DC
AC coupling
Bypassing
Signal Filters
Timing circuits
There are numerous varieties of capacitors. Appendix D shows some of the
most popular types of capacitors. The capacitor types are classified as:





Mica
Ceramic
Paper
Plastic
Electrolytic
In our lab sessions only ceramic and electrolytic capacitors will be used.
5.3.1 Ceramic capacitors
Ceramic dielectrics provide very high dielectric constant. Therefore, it
provides high capacitance values in a small physical size. They are used in
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High Frequency (10 – 60 MHz) applications. Typical example of its use is in
simple RC filters, studied later.
Figure 6 Ceramic Capacitor Symbol
The manufacturers mark the surface of the disk with a code that indicates
capacitance value, and these values typically range from 16 to 1600 pF. The
capacitance value can be found by interpreting different codes on the
surface of the capacitor; for instance:

Large capacitors have the value printed plainly on them, such as 10 µF
(Ten Micro Farads) but smaller disk types along with plastic film types
often have just 2 or three numbers on them.

IMPORTANT: Two numbers on the surface: these are read as PicoFarads. For example: 47 printed on a small disk can be assumed to
be 47 Pico-Farads.

Three numbers on the surface: It is similar to the resistor code. The
first two are the 1st and 2nd significant digits and the third is a
multiplier. The last digit tells you how many zeros to write after the
first two digits.
Table 6 shows the corresponding value for the third digit.
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First 2
digits
(example)
10
21
5
Third
Digit
0
1
2
3
4
5
6
7
8
9
Multiplier(this value times
Value (example)
the first two digits)
1
10 pico – Farad
10
210 pF
100
500 pF
1000
10 000
100 000
NOT USED
NOT USED
0.01
0.1
Table 6. Value for the third digit
For instance: A capacitor marked 104 is 10 with 4 more zeros or 100,000pF.
If the capacitor has a single letter after digits, that letter refers to the
tolerance value. Table 7 lists the equivalent values for the tolerance letter:
Letter symbol
Capacitor Tolerance
B
+/- 0.1%
C
+/- 0.25%
D
+/- 0.5%
E
+/- 0.5%
F
+/- 1%
G
+/- 2%
H
+/- 3%
J
+/- 5%
K
+/- 10%
M
+/- 20%
N
+/- 0.05%
P
+100% ,-0%
Z
+80%, -20%
Table 7. Capacitor tolerance
For example, a capacitor marked as 103J is interpreted as
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10,000 pF with +/-5% tolerance
5.3.2 Electrolytic capacitors
Electrolytic capacitors have an electrolyte between the two plates. Due to
the chemical reaction, a very thin layer of oxide is deposited on only the
positive plate. For this reason, they are polarized. The electrolytic
capacitors have all the information printed on the capacitor body including:
capacitance, voltage, temperature and polarity. The electrolytic capacitors
are prone to leakage over time, loosing their charging capacity. The most
common use of the electrolytic capacitors is in power supply filtering, simple
timing circuits and RC combination used to initialize flip flops and registers.
-
+
Figure 7. Electrolytic capacitor symbol
5.3.3 Capacitance Measurements

Use the DMM: press the CX push-button (switch), and make sure the
AC/DC switch is in the DC position.

Insert the capacitor leads into the CX (+) and CX (-) jacks. If the
capacitor is a polarized type, be sure to insert the negative lead in the
CX (-) jack, and the positive lead in the CX (+) jack.

Select the desired range. If the value is unknown, start with the
lowest range (2nF).

Read the capacitance value from the display panel, and record in your
Worksheet(WS).
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5.3.4 Finding capacitor nominal value
1. Using the procedure described, determine the capacitance value for
each capacitor and record the corresponding value in Table 8 in your
worksheet. The last column in Table 8 is the value of the capacitance
in Farads expressed in engineering notation. For example, for a 0.01
µF capacitance, the notation is derived as: 0.01 x 10 -6 = 10-2 x 10-6 =
10-8 F.
Code
103K
222K
333Z
223
101K
Value in
µF
Numerical Code
Tolerance
rd
1st
2nd
3
Digit Digit Digit
1
0
1000
+/- 10%
0.01
2
2
100
3
3
1000
2
2
1000
1
0
10
Table 8. Capacitor nominal value
Value in F-Eng. Notation
1x10-8
2. Then find each capacitor in the kit and enter the code in the first
column of Table 8, as shown by the example.
3. Find the tolerance for each capacitor and enter the value in Table 8.
4. Record the numerical value of each color in the 5th column, as shown
by the example.
5. Compute the value in microfarads and Farads (Worksheet) and record
it in Table 8.
5.3.5 The measured value of the capacitors
1. Read the capacitance value using the DMM for the capacitors shown in
Table 9. Following the instructions stated earlier about the use of the
DMM, record the measured value in the second column in Table 9.
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Choose the correct range that will provide the highest degree of
accuracy for the measurement.
2. Determine if the measured value falls within the specified tolerance,
and record it in Table 9 in your worksheet.
Standard
Capacitance
Falls within
Capacitor
Measured
Specified
Code
103K
Value
0.00916 uF
Tolerance(yes/No)
YES
222K
333Z
223
101K
Table 9. Measured value of capacitance
5.4 Procedure 4 – The Power Supply
In this procedure, you will familiarize yourself with
controls and indicators of the Analog Power Supply.
The
Tektronix
CPS250
Triple
Output
Analog
Power
Supply
is
a
multifunctional bench or portable instrument that has a fixed 5 volt output
(2A), and two variables up to 20 volt outputs (500mA).
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Figure 8. Power supply front panel
5.4.1 Controls and Indicators
These controls and indicators are important in determining how voltage is
supplied to a circuit. Refer to Figure 8 in this procedure to identify the
controls and indicators.
1. POWER Button. Push the top of the switch to the ON position to
turn the power supply on. Push bottom of the switch to the OFF
position to turn it off.
2. POWER ON Indicator. When lighted, LED (Light Emitted Diode)
indicates a power-on condition.
3. Voltage Meter. This meter indicates the voltage level of A/B
output, depending on the position of the A/B meter switch. The meter
may be mechanically set for zero with the slotted mechanical zero
adjust disk below the center of the meter.
4. Mechanical Meter Adjustment. These slotted, plastic disks allow
mechanical zero adjustment of outputs of the V and mA meters. The
mechanical zero adjustment allows to set the instrument indicator in
the initial position for the measurement (commonly is zero). Always
rotate the adjustment in the clockwise direction for optimum results.
5. A/B Meter Switch. This switch connects the V and mA meters to
the A or B output.
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6. Milliampere Current Meter. This meter indicates the current level
of A or B output, depending on the position of the A/B meter switch.
The meter may be mechanically set for zero with the slotted
mechanical zero adjust disk below the center of the meter.
7. A/B Output Switch. Switches A and B outputs from Independent to
Tracking Parallel or Tracking Series operation. When the switch is in
the tracking position, A Voltage and A Current controls set the level
of both A and B outputs. B Voltage and B Current controls are
inoperative when the A/B OUTPUTS switch is set to the TRACKING
position.
8. B Voltage Control. Rotate to set voltage at B output terminals when
A/B OUTPUTS switch is in the INDEPENDENT position. This control
is inoperative when A/B OUTPUTS switch is in the TRACKING
position.
9. B CURRENT Control. Rotate to set current level available at B
output when A/B OUTPUTS switch is in INDEPENDENT position.
Control is inoperative when A/B OUTPUTS switch is in the TRACKING
position.
10. A CURRENT Control. Rotate to set current level available at A
output when A/B OUTPUTS switch is in the INDEPENDENT position.
11. A VOLTAGE Control. Rotate to set voltage at A output terminals
when A/B OUTPUTS switch is in the INDEPENDENT position.
12. A Output. Positive (red) and negative (black) output for
independent 0 to 20 VDC, 0.5A maximum. LED lights when OVERLOAD
current limit is reached or exceeded.
13. B Output. Positive (red) and negative (black) output for
independent 0 to 20VDC, 0.5A maximum. LED lights when OVERLOAD
current limit is reached or exceeded.
14. 5V 2A Output. Positive (red) and negative (black) output for fixed
5 volts DC, 2A maximum. LED lights when OVERLOAD current limit is
reached or exceeded.
15. Chassis Ground Connector. The green binding post is connected
through the power cord to the power receptacle ground.
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5.4.2 How to set and display voltage
1. Turn the power supply ON.
2. See control switch 5 in the Figure 8, select one of the 2 output
circuits (A or B) by using the A/B Meter Switch (5).
3. Depending on the output channel (A or B) selected, adjust the voltage
to desired value by adjusting the knob under the A Voltage Control
(11) or B Voltage Control (8).
4. You will be able to see the adjusted voltage on the Voltage meter
indicator (3) in Figure 8.
5. Turn the POWER OFF after your observations.
5.5 Procedure 5 – The DC Power Supply and the Multi-meter
5.5.1 Voltage Adjustments:
In this procedure, you will use the power supply to apply different voltages
that will be measured by the DMM. This procedure is sometimes used to
obtain precise values of voltage from an analog power supply.
You will need two red test leads and two black test leads for this procedure.
EXERCISE
Part (a) of Procedure 5 – constant voltage measurement
Turn the DMM POWER ON.
1. Press the V function switch on the DMM.
2. Press the 20V/20mA/20kΩ/20nF Switch on the DMM.
3. Select DC measurement using the AC/DC switch. Set for DC
measurement by setting switch in disengaged position.
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4. Connect the red test lead to the red jack where V-OHM is written
and the black test lead to the COM jack.
5. Turn on the power supply.
6. Connect the second red test lead to the red jack in the 5V 2A and
the second black test lead to the black jack in the 5V 2A of the
power supply.
7. Connect the first black test lead with the second black test lead.
8. Connect the first red test lead with the second red test lead.
9.
Read the measured value from the DMM’s display panel and record
your observations in your WS.
10. Turn off all equipment and disconnect wires.
Part (b) of Procedure 5 – variable voltage measurement
1. Turn on the DMM.
2. Press the V function switch on the DMM.
3. Press the 20V/20mA/20kΩ/20nF Switch on the DMM.
4. Connect the red test lead to the red jack where V-OHM is written
and the black test lead to the COM jack.
5. Turn the POWER ON of the power supply.
6. Set the A/B Meter Switch to A.
7. Set the voltage to 10V by turning the A VOLTAGE Control knob
clockwise or counterclockwise. Make sure the A CURRENT Control is
set to MIN.
8. Connect the other red test lead to the red jack in the A section and
the black test lead to the black jack in the A section of the power
supply.
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9.
Read the measured value from the display.
10. Connect the first black test lead with the second black test lead.
11. Connect the first red test lead with the second red test lead.
12. Read the measured value from the DMM’s display panel.
13. Slowly turn the A VOLTAGE Control counterclockwise until you read
7V on the DMM’s display panel.
14. Slowly turn the A VOLTAGE Control clockwise until you read 12V on
the DMM’s display panel and record in your WS.
15. Turn off all equipment.
5.6 Procedure 6 – Soldering and Desoldering Techniques
Soldering is the most fundamental skill needed to assemble any electronic
project. From the college to the cutting edge research lab, it always is
necessary to have a skilled person in soldering. The practice is very
important in order to make the perfect joint. The idea is simple: to join
electrical parts together to form an electrical connection, using a molten
mixture of lead and tin (solder) with a soldering iron.
The details of soldering technique and examples of incorrect soldering are
shown in Appendix B. Please read Appendix B before continuing with the
following procedure.
EXERCISE
5.6.1 Soldering Practice
1. Clean the PCB and be sure that it is free from dirt and grease.
2. Find a 1-kΩ resistor in your kit. Use the same resistor in procedure
2.
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3. Insert the 1-kΩ Resistor in the PCB (Printed Circuit Board) and bend
the leads.
4. Try to secure it firmly and spread the wires outward.
5. Cut the wires to the correct length (see Appendix B, Figure 4).
6. Clean the tip of the hot soldering iron on a damp sponge.
7. Heat all parts of the left joint with the iron for under a second or so.
8. While heating the elements, apply sufficient solder to form an
adequate joint.
9.
Do not move the parts until the solder has cooled naturally.
10. Perform the same process for the right joint.
11. Remove and return the soldering iron safely to its stand.
Once the soldering process is complete the resistance is secured to the
PCB, it is shown in Figure 9a.
Figure 9a. PCB with a 1 KΩ Resistor
The back plane is shown in Figure 9b. The back plane image shows the
resistance before cut the wires and the soldering points once the
soldering process has been completed.
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Figure 9b PCB back plane (before cut the wires and after soldering process)
5.6.2 Desoldering
After the soldering practice, it is important to talk about possible errors in
the soldering process. Appendix B shows several soldering mistakes. These
types of errors are very common. When they occur, it is important to
correct them. Furthermore, for troubleshooting and repair, sometimes you
will need to remove a component that you have soldered onto a proto board.
This action is known as Desoldering. The final part of Appendix B shows the
most popular desoldering techniques used in our laboratories. Review them
carefully, and if it is necessary, ask your Laboratory Assistant (LA) for the
necessary equipment.
5.7 Procedure 7 – Measuring Voltage and Current
In this procedure, you will measure the current flowing through a 1KΩ
resistor and the corresponding voltage drop, when a voltage is applied to its
terminals.
For this procedure, the DMM, the power supply and two sets of test leads
will be used.
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5.7.1 Measuring voltage drop across a resistor:
1. Set the DMM to read a voltage of 5V (using A VOLTAGE Control).
2. Connect the black test lead from the power supply to one end of the
resistor and the red test lead to the other end of the resistor.
3. Connect the black test lead of the DMM to the end where the black
test lead of the power supply is connected and connect the red test
lead of the DMM to where the red test lead of the power supply is
connected as shown in Figure 10.
4. Set the power supply to supply a DC voltage of 5V.
5. Read the voltage displayed on the DMM.
6. Turn the power supply and DMM off and disconnect the test leads.
Figure 10. Voltage measurement setup
5.7.2 Measuring current flow through a resistor
1. Set the DMM to read a current of 2A.
2. Connect the black test lead from the DMM to one end of the resistor.
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3. Connect the red test lead of the DMM to the red test lead of the
power supply.
4. Connect the black test lead of the power supply to the other end of
the resistor (See Figure 11).
5. Set the power supply to supply a DC voltage of 5V (5V, 2A).
6. Read the value on the DMM’s display panel.
7. Record the values in your WS.
Answer: The current displayed on the DMM’s display panel is 4.976mA
8. Turn the power supply and DMM off and disconnect the test leads.
Figure 11. Current measurement setup
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6 Knowledge Evaluation:
Answer the following questions and record them in your WS:
1. What are the ohmic values and tolerances of the commercially
available carbon resistors shown in Table 10?
1
2
3
4
Brown
Black
Blue
Gold
Yellow
Violet
Orange
Gold
Brown
Gray
Gold
None
Red
Yellow
Silver
Gold
Green
Green
Brown
Blue
Green
Black
Silver
None
Value
Value
Table 10. Ohmic values
2. Describe the procedure for using the DMM to read the current
through a resistor in your own words.
Answer:
3. Describe the procedure for soldering a resistor in the PCB in your own
words.
Answer:
7 References:
For additional information about the topics related to this lab, see the
following references:
1. R. L. Boylestad, Introductory Circuit Analysis. Prentice Hall, 2003.
2. N. P. Cook, Introductory DC/AC Circuits. Prentice Hall, 1999.
3. T. L. Floyd, Principles of Electric Circuits. Prentice Hall, 2003.
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4. Transtronics, KS. How to Read Capacitor Codes.[Online]. Available:
http://xtronics.com/kits/ccode.htm
5. Alan Winstanley. (1997). The Basic Soldering Guide Photo Gallery. [Online].
Available: http://www.epemag.wimborne.co.uk/solderpix.htm
6. Lynwood Hobbs. Resistors and their uses [Online]. Available:
http://www.ipass.net/teara/resistor.html
7. Tony Van Roon. Capacitors [Online]. Available:
http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html
8. CLAB resources [Online]. Available:
http://cot-vyger.cougarnet.uh.edu
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