universiti malaysia perlis dkt 111/3 – electric...

Universiti Malaysia Perlis

DKT 111/3 – ELECTRIC CIRCUITS PRINCIPLES

LAB ASSIGNMENT 1

PART A :INTRODUCTION TO LABORATORY EQUIPMENT (MULTIMETER)PART B : COMPONENT CODING AND RESISTOR MEASUREMENT

Pn. Nazatul Syima Bt. SaadPusat Pengajian Kejuruteraan Komputer Dan Perhubungan

DKT111/4 ELECTRIC CIRCUIT PRINCIPLE LABORATORY MODULE

Universiti Malaysia Perlis

LAB ASSIGMENT 1 (PART A)INTRODUCTION TO LABORATORY EQUIPMENT (MULTIMETER)

OBJECTIVE

1. To familiarize students in using multimeter to measure resistance, voltage and current as a basic tool in measurement.

2. To make students understand how to do real connections or wiring in the laboratory based on the given schematic diagram using breadboard to easily connect components together to build circuits.

INTRODUCTION

BREADBOARD

When building a "permanent circuit" the components can be "grown" together (as in an integrated circuit), soldered together (as on a printed circuit board), or held together by screws and clamps (as in house wiring). In lab, we want something that is easy to assemble and easy to change. We also want something that can be used with the same components that "real" circuits use. Most of these components have pieces of wire or metal tabs sticking out of them to form their terminals.

A breadboard is used to make up temporary circuits for testing or to try out an idea. No soldering is required so it is easy to change connections and replace components. Parts will not be damaged so they will be available to re-use afterwards.

Figure 1.3: Front look of a typical small breadboard used in the laboratory

The breadboard has many strips of metal (usually copper) which run underneath the board.

Figure 1.4: The metal strips layout

When wiring, it is important to keep your work neat! This will save time in debugging when your circuit doesn’t work. Here are some tips: Keep your wires short, do not loop wires over

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the chip, use the bus lines for Ground or a DC supply voltage (e.g. VCC) and sometimes to get cleaner signals, short the metal base of the breadboard to the circuit’s ground.

MULTIMETER

Multimeter is a basic tool in electric and electronic fields. It is a multipurpose device to measure voltage, current and resistance. Basically there are two types of multimeter used either in the education or industrial field based on the electronic circuits inside them: analog and digital meters. The analog meter, broadly known as VOM (volt-ohm-miliammeters) uses a mechanical moving pointer which indicates the measured quantity on a calibrated scale. It requires the user a little practice to interpret the location of the pointer. The digital meter broadly known as DMM (digital multimeter) used number or numerical display to represent the measured quantity. It has high degree of accuracy and can eliminate usual reading errors compared to the analog meters. Students should be adept at using both meters throughout their studies.

Resistance Measurement: For VOM always reset the zero-adjust whenever you change scales. In addition always choose the range setting that will give the best reading of the pointer location. As an example, to measure a 500-Ω resistance, choose function switch resistance with a range setting of X 1k. Finally do not forget to multiply the reading by the proper multiplication factor. If you are not sure about the value always starts with the highest range and going downwards until appropriate scale is chosen. For DMM remember that any scale marked “kΩ” will be reading in kilo-ohms and any with “MΩ”scale in mega-ohms and so on. There is no zero-adjust on a DMM meter but make sure that the resistance reads zero when shunting both leads. Polarity does not concern in resistance measurement. Either lead of the meter can be placed on either terminal end of the component, it will be the same.

Voltage Measurement: When measuring voltage levels, make sure the meter is connected in parallel with the element whose voltage is to be measured. Polarity is important because the reading will indicate up-scale or positive reading for correct connection and down-scale or negative reading if reverse connection of the meter test leads to the resistor’s terminals. Therefore a voltmeter is not only excellent for measuring voltage but also for polarity determination. Choose the correct function switch for example DCV to measure dc voltage and turn to the range switch that has slightly bigger value than the voltage to be measured.

Current Measurement: When measuring current levels, make a series connection between the meter and the component whose current is to be measured. In other words, disconnect the particular branch and insert the ammeter. The ammeter also has polarity marking to indicate the manner they should be hooked-up in the circuit to obtain an up-scale or positive measurement. For analog meter pay attention that reversing the polarity of the meter may cause damage to the pointer. Again always start with higher range going downwards to avoid damaging the instrument.

The connection of the multimeter to measure different electrical quantities is shown in both schematic diagram and real wiring illustration in the laboratory in Figure 1.5.

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R

V sA

V /Ω

Figure 1.5(a): Schematic diagram

Multimeter as Ohm Meter

Experiment 1

Connect the meter's test probes across the resistor as such, and note its indication on the resistance scale:

Figure 1.6 – Measuring resistors

If the needle points very close to zero, you need to select a lower resistance range on the meter, just as you needed to select an appropriate voltage range when reading the voltage of a battery.

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Experiment 2

Figure 1.7 - Measuring breadboard’s continuity.

Use your meter to determine continuity between the holes on a breadboard as in Figure 6. (Use small gauge solid wire to insert into the holes of the breadboard), redraw the board with line showing its connectivity.

Experiment 3

Figure 1.8 – Measuring circuit resistance

For the circuit below ( figure 7) , measure the voltage between point ab, whena) R1 = 1 kΩ, R2 = 2.2 kΩ and R3 = 4.7kΩ.b) R1 = 200 kΩ and R2 = R3 =10 kΩ.

Multimeter as Volt Meter

Voltmeter is an electrical instrument which is use to measure potential difference between two points. Potential difference or voltage between points are measure in volts, V. Bigger voltage value indicates current from higher potential terminal has more energy and are readily to move to lower potential terminal. Voltage is a vector quantity and always measure

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between two points. Point voltage refers the voltage of that single point to a common point (electrical ground). Voltmeter has very high internal resistance, and is connected in parallel across components.

Figure1.9 – Voltmeter connection in parallel

Reading the Voltage Scale

Figure 2.0 – Analog Multimeter’s Screen

The actual reading of a voltmeter is made up of the combination of selector’s voltage range and meter reading (needle position). Three different scales are available (10, 50 and 250) on an analog voltmeter.

Measured voltage = voltage range x corresponding meter reading (needle)

ExampleThe measurement shown in Figure 3 may be:

1) Range selection = 10Measured voltage = 4.4 V

2) Range selection = 1000Measured voltage = 440 V

3) Range selection = 0.1Measured voltage = 0.44 V



6) Range selection = 2.5Measured voltage = 1.1 V

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Experiment 1

Figure 2.1 – Series LED circuit

On your breadboard, construct the circuit as shown in Figure 5. Connect battery terminal to DC power supply and sweep the supply voltage from 0.0 V to 40.0 V. Measure the voltages across R1(1 kΩ), D1, D2 and D3 for all supply voltage and calculate the point voltages as shown in Table 1.

No Supply Voltage (V)

VR1 VD1 VD2 VD3 VA VB VC VD VE

1 8.02 10.03 12.04 14.05 16.06 18.07 20.0

Table 1 – Voltage measurement

Multimeter as Ammeter

The actual reading of an ammeter is made up of the combination of selector’scurrent range and meter reading (needle position). The Ampere scale uses thesimilar scale of the voltmeter

Measurement1. Point selector to highest current range.2. Touch the probe leads across measurement points (red terminal to currententry point).3. If the reading is too small, disconnect probe and adjust range until readablevalue is obtained.

Caution1. Never connect Ammeter in parallel.2. Always disconnect probe when adjusting the range selector.

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Experiment 1

Referring to figure 1.8 measuring the current cross each resistor with Voltage supply 3V.

Resistor Current R1R2R3

~ ooooo End ooooo~

APPENDIX A: SANWA ANALOG METER

Figure A1: Names of components

a) Precaution for safety measurement

i. To ensure that the meter is used safely, follow all safety and operation instructions.

ii. Never use meter on the electric circuit that exceed 3kVA.

iii. Never apply an input signals exceeding the maximum rating input value.

iv. Pay special attention when measuring the voltage of AC30Vrms or DC60V or more to avoid injury.

v. Always keep your fingers behinds the finger guards on the probe when making measurements.

vi. Before starting the measurement, make sure that the function or range properly set in accordance with he measurement.

vii. Be sure to disconnect the the test pins from the circuit when changing the

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function or range.

viii. For details, please refer instruction manual.

b) Preparation for Measurement

i. Adjustment of meter zero position

Turn the zero position adjuster so that the pointer may align right to the zero position.ii. Range selection: Select a range proper for the item to be measured. Set the range

selector knob accordingly.

c) Measuring DCV

i. Set the range selector knob to an appropriate DCV range.ii. Apply the black test pin to the minus potential of measured circuit and the red

test pin to the plus potential as in Figure A2.iii. Read the move of the pointer by V and A scale.

Figure A2

d) Measuring DCV (NULL)

i. Set the range selector knob to an appropriate range.ii. Turn the adjuster so that the pointer may align exactly to 0 by DCV scale.iii. Apply the black test pin to the negative potential side of the circuit and the red

test pin to the positive potential side as in Figure A3.iv. Read the move of the pointer by DCV scale.

Figure A3

e) Measuring ACV

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i. Turn the range selector knob to an appropriate ACV range. ii. Apply the test leads to measured circuit as in Figure A4. iii. Read the move of the pointer by V and A scale. (Use AC 10V scale for 10V range

only)Note: Since this instrument employs the mean value system for its AC voltage measurement circuit, AC waveform other than sine wave may cause error.

Figure A4

f) Measuring DCA

i. Connect the meter in series with the load.ii. Turn the range selector knob to an appropriate DCA range. iii. Take out measured circuit and apply the black test pin to the minus potential of

measured circuit and the red test pin to the plus potential as in Figure A5.iv. Read the move of the pointer by V and A scale.

Figure A5

g) Measuring Resistance (Ω)

Precaution: Do not measure a resistance in a circuit where a voltage is present.

i. Turn the range selector knob to an appropriate Ω range.ii. Short the red and black test pins and turn the 0Ω adjuster so that the pointer may

align exactly to 0Ω. (If the pointer fails to swing up to 0Ω even when the 0Ω adjuster is turned clockwise fully, replace the internal battery with a fresh one.)

iii. Apply the test pin to measured resistance as in Figure A6.iv. Read the move of the pointer by Ω scale.v. Note: The polarity of (+) and (-) turns reverse to that of the test leads when

measurement is done in Ω range.

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Figure A6

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LAB ASSIGMENT 1 (PART B)COMPONENT CODING AND RESISTOR MEASUREMENT

OBJECTIVE

1. To acquaint students with the skill to read resistor and capacitor values based on color code and digital/alphabet code.

2. To make students understand how to do real connections or wiring in the laboratory based on the given schematic diagram using breadboard to easily connect components together to build circuits.

INTRODUCTION

RESISTOR CODING

The color code technique is used to show resistance values of carbon resistors without having to measure it. In this technique color bands are printed on the resistor. The procedure for determining the resistance of a color-coded resistance is described in Table 1. The first two bands determine the first two digits of the resistor value, while the third band determines the power of 10-multiplier. For the resistor with value less than 10 Ω the third band is either silver or gold. The forth band is the percent tolerance for the chosen resistor. If resistors have only three bands, it means the forth band has no color. Sometimes a fifth band is employed for some high precision resistor where the first three bands represent the significant digit. The forth band is the multiplier while the fifth band is the tolerance. In the other case, for some standard 4-band code, a fifth band may indicate the manufacturer’s special code for some physical characteristic or failure rate of the component.

For increasing wattage, the size of resistor will increase accordingly. The larger sized resistors from about 5 W and up or wire winding resistors are not color-coded but are using digital and alphabet code printed on its body. In writing the value of resistors: k stands for multiplier “kilo” and M for multiplier “mega”. The alphabet written after the resistor value shows the tolerance: F = 1%, G = 2%, J = 5%, K= 10% and M = 20%.

Resistance should never be measured in a live network due to the possibility of damaging the meter with excessively high currents and obtaining readings that have no meaning. In a constructed circuit, to measure a single resistance value, just take off one end of its terminal to avoid the effect of other resistances in the circuit. This applies in the same manner to the other components such as capacitor and inductor.

The standard code is adopted by manufacturer through their trade association, the Electronic Industries Association (EIA).

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Color 1st Band(1st Significant Digit)

2nd Band(2nd Significant Digit)

3rd Band(Multiplier)

4th Band(Tolerance)

Black 0 0 1Brown 1 1 101 1%Red 2 2 102 2%

Orange 3 3 1 03 3%Yellow 4 4 104 4%Green 5 5 105

Blue 6 6 106

Violet 7 7 107

Grey 8 8 108

White 9 9 109

Gold - - 0.1 5%Silver - - 0.01 10%

No Color - - - 20%

Table 1.1: Resistor color coding

Figure 1.1: Reading resistor color codingExample 1:

Example 2:

R33F = 0.33 ±1% Ω 6k8J = 6.8 x 103 Ω ±5%4k7 = 4.7 x 103 Ω R39 = 0.39 Ω10R0 = 10 Ω 2k2M = 2.2 x 103 ±20%200R = 200 Ω 1R0 = 1 Ω

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The value of this resistor is 25 x 101± 10% = 250± 10% ohms


CAPACITOR CODING

Same as resistors, most of the capacitors have their nominal value printed directly on them using digital/alphabet code according to the EIA coding system. This code is generally given in picofarads (pF), which means that we need to manipulate the value if we want the value in microfarads (µF) or nanofarads (nF). Some capacitors have polarity (positive and negative) which must be connected according to their polarity in order for the capacitor to operate such as the electrolytics capacitors. Normally the negative leg of electrolytics capacitor could be recognized by the white stripes at the body and/or the negative leg is shorter then the positive leg.

Some types of capacitors are shown in Figure 1.2 below.

Figure 1.2: Different types of capacitors construction

Example 3:

Capacitor marked 104 has value of 10 with 4 zeroes after it, or 100,000pF (equivalent to 100 nF or 0.1 µF) Capacitor marked 681 = 68 with single zero or 680 pFCapacitor marked 472 = 47 with 2 zeroes or 4700 pF (equivalent to 4.7nF) Alternatively, the value may be given directly in nanofarads with three significants digits but the thirds generally ‘0’. In this case there is generally also a small ‘n’ which can be used in place of decimal points.

Example 4:

Capacitor marked 220n has 220nF capacitances (equivalent to 0.22F)Capacitor marked 3n3 has 3.3nF capacitances (equivalent to 3300pF)

Some of the capacitors have a capital letter to indicate their tolerance rating. Below is capacitor tolerance marking codes:

F± 1%

G± 2%

J± 5%

K± 10%

M± 20%

Z-20%, +80%

Example 5:

104K = 0.1µF ± 10%, 4n7J = 4.7nF ± 5%

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Figure 1.5(b): Real wiring diagram for illustration

EQUIPMENT/COMPONENT

Multimeter (1)Adjustable DC power supply (1)Resistor (1/4 W) – 1 kΩ , 2.2 kΩ, 4.7 kΩ, 15 kΩ,

680 Ω, 27 kΩ, 3.9 kΩ Breadboard (1)

**For non-measured resistor and capacitance values students are strictly required to complete the answers before the lab session. Otherwise they will be forbidden from participating the session.

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PROCEDURE

PART A: READING RESISTOR BY COLOR CODING

Determine the nominal value or color bands of a particular resistor based on color coding technique for each case given in Table 1.2 below. Check your answers with the measured values in the laboratory.

COLOR BAND

No. Band 1 Band 2 Band 3 Band 4 Nominal Value

Measured Value (Ω)

Within Tolerance?

YES/NO1. brown black red gold2. blue grey brown gold3. yellow violet orange gold4. red red orange gold5. 3.9kΩ ± 5%6. 15kΩ ± 5%7. 27kΩ ± 5%

Table 1.2: Exercise for determining resistor values by color coding and measurement

PART B: READING RESISTOR AND CAPACITOR BY DIGITAL/ALPHABET CODING

Determine the nominal value of a particular resistor based on digital/alphabet coding technique for each case given in Table 1.3 below.

DIGITAL/ALPHABET CODE NOMINAL VALUE (in ohm)3k91R08M5R56

Table 1.3(a): Exercise for determining resistor values by digital/alphabet coding

DIGITAL/ALPHABET CODE NOMINAL VALUE( in nanofarad)33J1043n3J103Z

Table 1.3(b): Exercise for determining capacitor values by digital/alphabet coding

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PART C: USING MULTIMETER TO MEASURE RESISTANCE, VOLTAGE AND CURRENT

EXERCISE 1:

Using the supplied equipments/components in the laboratory, hook-up the series resistive circuit as in Figure 1.6. As a common practice, always measure the actual value of the resistors used in the circuit and set the source value using multimeter to reduce errors from the expected results. Perform the following instructions.

Figure 1.6: Simple series resistive circuit

1. Measure currents I1 and IT. Should they be the same? Give your reason.Answer:

I1 = ________ mA IT = ________ mA

Comment: ________________________________________________________________________________________________________________________________________________

2. Measure voltage drop across resistor R1.Answer:

VR1 = ________ V

3. Measure voltage drop across the combination resistors R2 and R3.

Answer:

VR2R3 = ________ V

4. Disconnect the power supply and measure the total resistance in the circuit, Req.Answer:

Req = ________ Ω

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Measured values:R1 = ________ ΩR2 = ________ ΩR3 = ________ Ω


EXERCISE 2:

Modify the previous series circuit connection to reconstruct a parallel resistive connection as in Figure 1.7. Perform the following instructions;

Figure 1.7: Simple parallel resistive circuit

1. Measure currents I1, I2, I3 and IT as indicated in the above diagram using miliammeter.Answer:

I1 = ________ mA I2 = ________ mA I3 = ________ mA IT = ________ mA

Comment: ________________________________________________________________________________________________________________________________________________

2. Use the ohmmeter to measure the equivalent resistance Req of this circuit. Does the result equal to the one measured in Exercise 1?

Answer:

Req = ________ Ω

Comment: ________________________________________________________________________________________________________________________________________________

3. Measure voltage drop across R1, R2 and R3. What can you conclude from these results? Answer:

VR1 = ________ V VR2 = ________ V VR3 = ________ V

Comment:

__________________________________________________________________________________________________________________________________________________

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Discussion:

Conclusion:

~oooo000oooo~

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