EEEB111_Lab 1 (Introduction to Resistance Measurement)

EEEB 111 ELECTRICAL/ELECTRONICS MEASUREMENT LABORATORY - UNITEN Exp. 1, Page 1/14

EEEB111

ELECTRICAL/ELECTRONICS

MEASUREMENT LABORATORY

Experiment 1:

Introduction to Resistance Measurement


EXPERIMENT 1

Introduction to Resistance Measurement

Assessed OBE Course Objective: CO1

OBJECTIVES

The objective of this laboratory experiment is to introduce the students to measurement of resistances using digital and analogue measuring equipment and to determine the internal connections of the

protoboard.

INTRODUCTION

Electrical components that will be used in this course include the resistor, capacitor, inductor, and the

operational amplifier. Components will be connected to one another on a protoboard and then

connected to one or more voltage sources.

The voltage sources include the DC power supply for constant voltages, and the function generator for

the time-varying voltages. In this experiment, you will learn to build a DC series resistive circuit and to make current, resistance and voltage measurements for that circuit.

A. Resistors:

Resistors are cylindrical shaped components with leads at either end. The resistance in ohms (Ω)

associated with the resistor is specified by a colour code (see Table 1.1) in the form of bands

painted on the body of the resistor (see Figure 1.1).

a. The first band is located nearest the end of the resistor, and specifies the first significant digit

of the resistance.

b. The second band specifies the second significant digit.

c. The third band tells the power of the ten by which the two-digit number is multiplied to obtain

the resistor value.

d. The fourth band indicates the tolerance and is set slightly further from the third band.

Figure 1.1: Resistor’s Colour Band


Table 1.1: Colour Codes for Resistors

First band Second band Third band Fourth band

Digit Digit Multiplier Tolerance

Black 0 Black 0 Black 1.0 Violet ± 0.1 %

Brown 1 Brown 1 Brown 10.0 Blue ± 0.25%

Red 2 Red 2 Red 100.0 Green ± 0.5 %

Orange 3 Orange 3 Orange 1000.0 Brown ± 1.0 %

Yellow 4 Yellow 4 Yellow 10000.0 Red ± 2.0 %

Green 5 Green 5 Green 100000.0 Gold ± 5.0 %

Blue 6 Blue 6 Blue 1000000.0 Silver ± 10.0%

Violet 7 Violet 7 Silver 0.01 No Band ± 20.0%

Grey 8 Grey 8 Gold 0.1

White 9 White 9

Example: A resistor with the colour code Yellow(4)-Violet(7)-Red(100)-

Silver(±10.0%)would have a resistance of 47 multiplied by 100 with a plus

or minus 10% manufacturing tolerance, i.e. 4700Ω ± 470Ω. Thus when measured

with an ohm-meter, the resistance must lie between 4230Ω (minimum value)

and 5170Ω (maximum value).

Resistance measurement of a resistor on an ohm-meter would give the actual resistive value

compared to the nominal (colour code) value.

The size of the resistor is related to its power rating. If the product of the voltage and current

associate with a resistor in a particular circuit exceeds the power rating, the power resistor will get too

hot and be destroyed. Only quarter (1/4)watt resistors can be used on the protoboard supplied for this

laboratory.

The total resistance, RT of a series circuit is the sum of the individual resistances.

n21T R......RRR +++=

The total resistance, RT of a parallel circuit is given by:

n21T R

1.......

R

1

R

1

R

1+++=


B. Protoboard:

The protoboard is used for circuit assembly. It appears as a symmetrical arrangement of holes, see Figure 1.2.

There are unseen metal (copper) strips located beneath the protoboard holes, which connect

rows or columns of these holes. These metal strips allow for conductivity between certain sets of

holes.

Figure 1.2: Protoboard Connection

Electrical components such as resistors, inductors and capacitors are mounted on the protoboard.

Crocodile clipped hook-up wires are used to connect power supply sources and decade boxes with

the internal wiring of the proto-board to complete the circuit.

Only No. 22 wires may be inserted into the proto-board. Wires should be stripped less than ¼"

before insertion into the board to avoid the possibility of short circuits during circuit

construction.

Likewise, resistors should be inserted no more than ¼" into the proto-board.

Since resistors will be used again, the ends of resistors should not be cut off.

In a typical protoboard the holes are connected either vertically or horizontally. There are 2 ways

to check the continuity or connections on the protoboard:

1. Resistance Display: When there is zero resistance (0Ω), measured by appropriate meter,

between each pair of holes in a row or column of the proto-board, this means the holes in that

row or column are all connected by a metal strip underneath the holes. When the resistance

between two holes is very large (value in MΩs) or overloaded (OL), those holes are not

connected.

2. Continuity Beeper: The continuity test determines whether a circuit is intact (i.e. has a

resistance less than about 30). To perform a continuity test, press, and connect test leads. The

beeper emits a single beep when there is no intact (OL), and emits a continuous tone when a

circuit has intact (approximate 0Ω).


Figure 1.3: Example of Continuity Beeper Check (Fluke 45 Dual Display Multimeter Users Manual)

C. Digital and Analogue Multimeters

To measure the resistance of a component, it must not be connected in a circuit.

If you try to measure resistance of components in a circuit, you will obtain false readings (even if

the supply is disconnected) and you may damage the measuring meter.

An analogue meter used to measure voltage, current and resistance; utilize an electromechanical

sensing mechanism, which causes deflection of a pointer along a continuous scale.

A digital meter employs circuitry that converts analog (continuous) signals to digital form and

shows the measured value in a digital display.

Multi-purpose meters such as Analog Volt-Ohm Multimeter (VOM) and the Digital Multimeter

(DMM) measure voltages, currents and resistances when switched to the appropriate scales.

The techniques used for each type of meter are very different.


1. Measuring Resistance with a Digital Multimeter

Figure 1.4: Voltage, Resistance or Frequency Measurement

(Fluke 45 Dual Display Multimeter (DMM) Users Manual)

1. Set the meter to the resistance range.

2. Put the probes across the component to be measured. Avoid touching the component at

any time or your resistance will upset the reading!

This is the digital multimeter model currently available at the lab:

Figure 1.5: Digital Multimeter (DMM)

(Fluke 45 Dual Display Multimeter Users Manual)


2. Measuring Resistance with an Analogue Multimeter

The resistance scale on an analogue meter is normally at the top, it is an unusual scale because it reads backwards and is not linear (evenly spaced).

1. Set the meter to a suitable resistance range. Choose a range so that the resistance you

expect will be near the middle of the scale.

2. Hold the meter probes together and adjust the control on the front of the meter which

is usually labeled "0 ADJ" until the pointer reads zero. If you can't adjust it to read

zero, the battery inside the meter needs replacing.

3. Put the probes across the component. Avoid touching the component at any time or your

resistance will upset the reading!

For resistance use the upper scale, noting that it reads backwards and is not linear (evenly spaced).

The scale is logarithmic i.e. the per unit scale value increases with every scale change. Check the

setting of the range switch so that you know by how much to multiply the reading.

Figure 1.6: VOM Display

Example: The needle reading on the scale in Figure 1.6 shows ‘26’. Thus,

when using the:

a. x 10Ω range, the resistance is 26 x 10Ω = 260Ω b. x 1kΩ range, the resistance is 26 x 1kΩ = 26kΩ

This is the analogue multimeter model currently available at the lab:

Figure 1.7: Analogue Multimeter (VOM)

(Sanwa YX360-TRF Analogue Multitester Users Manual)

Read at

Ω scale


UNIVERSITI TENAGA NASIONAL

Department of Electronics and Communication Engineering

College of Engineering

Semester: I / II / Special Academic Year: 20 ….. / 20 …..

COURSE CODE: EEEB111 EXPERIMENT NO.: 1

LAB INSTRUCTOR: DATE: TIME:

TITLE: Introduction to Resistance Measurement

OBJECTIVES: The objective of this laboratory experiment is to introduce the students to measurement of

resistances using digital and analogue measuring equipment and to determine the internal

connections of the protoboard.

PRE-LAB: MARKS:

EXPERIMENTAL RESULTS:

Part A : Resistance Measurement

Table 1.2

Table 1.3

/2.5

/2.5

Table 1.4

/12

Part B : Protoboard Connections

Figure 1.8

/2

Part C : Series and Parallel Resistive Circuits

Table 1.5

Table 1.6

/2.5

/2.5

POST-LAB:

Q1

/3

CONCLUSIONS: /3

INSTRUCTOR’S COMMENTS: TOTAL:

/30

STUDENT NAME: STUDENT ID: SECTION:

GROUP MEMBER: STUDENT ID:


EQUIPMENT 1. Resistors: 100 Ω, 220 Ω, 1 kΩ, 3.3 kΩ, 10 kΩ, 47 kΩ, 180 kΩ and 1.2 MΩ

2. Analogue Multimeter (VOM)

3. Digital Multimeter (DMM)

4. DMM Probes x 2nos. 5. Protoboard

6. Wire 22 AWG x 2nos.

PROCEDURES

The purpose of this first experiment is to acquaint you with the laboratory equipment, so do not rush.

Learn how to read the meter scales accurately and take your data carefully.

If you are uncertain about anything, do not hesitate to ask your instructor.

Part A: Resistance Measurements

Before learning to measure resistance, you need to first learn how to identify the nominal numerical

values of resistors according to their colour codes.

a. Refer to Colour Codes for Resistors in Table 1-1 and identify each resistor according to the

nominal resistance given in Table 1.2.

b. Fill in Table 1.2 for resistor colour codes and numerical values.

Table 1.2: Resistor Colour Code Identification & Numerical Value

Nominal

Resistance (Ω)

Resistor Bands – Colour Code Resistor Bands

– Numerical Value

1st 2nd 3rd 4th 1st 2nd 3rd 4th

e.g. 10k Brown Black Orange Gold 1 0 103 5%

100

3.3k

47k

180k

1.2M


c. Calculate the minimum and maximum resistance values.

d. Fill in Table 1.3 accordingly.

Table 1.3: Minimum and Maximum Resistances

Nominal Resistance

(Ω)

Minimum Resistance

(Ω)

Maximum Resistance

(Ω)

e.g. 10k 9.5k 10.5k

100

3.3k

47k

180k

1.2M

e. Measure the resistance of each resistor with DMM and VOM.

f. Fill in Table 1.4 accordingly.

g. Calculate the percentage error using the following formula:

100%value Nominal

value Measuredvalue NominalError ×

−=%

h. Check for the DMM measurement values; are all the resistors within the specified tolerance

range? If not, repeat the measurement.

Table 1.4: Finding Percentage Error

DMM (digital meter) VOM (analogue meter)

Nominal Resistance

(Ω)

Measured Resistance

(Ω)

Within specified Tolerance? (Yes/No)

% Error

Measured Resistance

(Ω)

Within specified Tolerance? (Yes/No)

% Error

10k

100

3.3k

47k

180k

1.2M


Part B: Protoboard Connections

a. Use two No. 22 wires that have been stripped ¼ inches at each end.

b. For each wire, insert one end into a pair of protoboard holes to be tested.

c. Connect the other end of each wire to the DMM probes. - One wire end should be connected to the red probe (positive) and the other wire end to the

black probe (negative).

d. Try both the Resistance Display and the Continuity Beeper connections test methods.

- Measure the resistances between enough pairs of holes so that you can determine how the

rows and columns on the protoboard are connected. Refer to the continuity tests,

explained in the theory part earlier, to interpret the readings.

e. Once the protoboard continuity of connections are known, draw the metal connections

underneath the holes on the protoboard in Figure 1.8:

Figure 1.8: Protoboard Connections


Part C: Series and Parallel Resistive Circuits

1. Series Resistive Circuit

a. Construct the circuit of Figure 1.9 on the protoboard.

Figure 1.9: Two Resistors in Series

b. Measure the actual value of each resistor shown, using DMM.

c. Measure for the total equivalent resistance RT by putting the DMM probes across the

terminals a-b.


e. Calculate the theoretical value of RT.

Table 1.5: Series Resistance Measurement

Measured R1

(Ω)

Measured R2

(Ω)

Measured RT

(Ω)

Theoretically calculated RT

(Ω)

% Error

R1 = 220 Ω

R2 = 100 Ω

RT

a

b


2. Parallel Resistive Circuit

a. Construct the circuit of Figure 1.10 on the protoboard.

Figure 1.10: Two Resistors in Parallel

b. Measure the actual value of each resistor shown, using DMM.

c. Measure for the total equivalent resistance RT by putting the DMM probes across the

terminals a-b.


e. Calculate the theoretical value of RT.

Table 1.6: Parallel Resistance Measurement

Measured R1

(Ω)

Measured R2

(Ω)

Measured RT

(Ω)

Theoretically calculated RT

(Ω)

% Error

R1 = 1 kΩ R2 = 3.3 kΩ RT

a

b


POST-LAB ASSIGNMENT

1. State and elaborate briefly on two (2) relative advantages of a digital multimeter over an analogue

multimeter, based on your lab experience.

CONCLUSIONS:

List THREE (3) main understandings that you have gained from this experiment.

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EEEB111_Lab 1 (Introduction to Resistance Measurement)