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In-02-08 Practical Tasks

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					Abu Dhabi National Oil Co. ADNOC Technical Institute

INSTRUMENTATION
INDUSTRIAL ELECTRONICS I

UNIT 8 PRACTICAL TASKS

INDUSTRIAL ELECTRONICS I - PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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UNITS IN THIS COURSE

UNIT 1

THE ELECTRICAL CIRCUIT

UNIT 2

SERIES AND PARALLEL CIRCUITS

UNIT 3

ELECTROMAGNETIC PRINCIPLES

UNIT 4

BASIC ELECTROSTATICS AND THE CAPACITOR

UNIT 5

THE INDUCTOR, CAPACITOR AND D.C.

UNIT 6

A.C. PRINCIPLES

UNIT 7

COMMON ELECTRICAL SYMBOLS

UNIT 8

PRACTICAL TASKS

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TABLE OF CONTENTS
Paragraph PRACTICAL TASK 1 PRACTICAL TASK 2 PRACTICAL TASK 3 PRACTICAL TASK 4 PRACTICAL TASK 5 PRACTICAL TASK 6 PRACTICAL TASK 7 PRACTICAL TASK 8 PRACTICAL TASK 9 PRACTICAL TASK 10 PRACTICAL TASK 11 PRACTICAL TASK 12 PRACTICAL TASK 13 RESISTANCE COLOUR CODES Page 4 7 9 11 12 13 14 17 20 23 26 29 33 37

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PRACTICAL TASK 1 PROOF OF OHM’S LAW
+ A + + DMM VARIABLE D.C. SUPPLY  V  VOLTS RANGE DMM RANGE mA 100  (2W) 

1. Connect the circuit as shown using the components supplied. 2. After the instructor has checked the circuit, switch on the D.C. supply and set the supply voltage to 1V on the voltmeter. Write down the current reading on the table provided. 3. Repeat step (2) for a D.C. supply setting of 2V to 10V. Increase the supply in one volt steps. Note the current reading each time. 4. Switch off the D.C. supply. 5. Plot a graph of voltage against current from the readings obtained. 6. The graph must be a straight line to show Ohm’s law. V  I. 7. Find the slope of the graph. 8. The slope of the graph will be the value of the resistor.
10V V

5V X

0 Y  (mA)

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ADNOC TECHNICAL INSTITUTE Slope = Distance X (Volts) Distance Y (mA) RESULTS TABLE VOLTMETER (VOLTS) 0 1 2 3 4 5 6 7 8 9 10 AMMETER (mA) 0 = Resistance

0uestions to be answered to show understanding of the practical task. (1) What is the current, if the supply voltage is 25 volts?

................................................................................................ ................................................................................................ ................................................................................................ (2) What is the circuit current with a supply voltage of 10V, if the resistor is changed to 300 ? ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 2 THE SERIES CIRCUIT
 A A B RANGE mA IS 10  (2W) P  V Q  R  20  (2W) V S  T  30  (2W) V U  D C A   RANGE mA  R1 R2 R3

 D.C. SUPPLY 10 VOLTS 

1. Connect the circuit as shown using the components supplied. Do not connect the meters. 2. After the instructor has checked the circuit, set the supply voltage to 10V with the voltmeter. Switch off. 3. Connect an ammeter across A-B. Switch on and note the ammeter reading. Switch off. 4. With the ammeter across A-B short out C-D. Switch on and note the reading. Switch off. 5. Short out A-B and connect the ammeter across C-D. Switch on and note the reading. Switch off. 6. The above readings should show that in a broken series loop, the current is zero. Also the current is the same in all parts of a series circuit. 7. Short out A-B and connect an ammeter across C-D. Switch on. 8. Connect a voltmeter across P-Q, R-S and T-U in turn and note the reading of each. Switch off. 9. The voltage readings obtained will prove KIRCHHOFF’s second law.

VSUPPLY = VPQ + VRS + VTU

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ADNOC TECHNICAL INSTITUTE 10. Divide the supply voltage (10V) by the total resistance (RT) for a series circuit. RT = 10 + 20 + 30 = 60 This will give the reading measured on the ammeter within the tolerance of the resistor values and the accuracy of the meters. RESULTS TABLE OPERATION
CIRCUIT CURRENT C-D OPEN CIRCUIT CURRENT C-D SHORTED CIRCUIT CURRENT A-B SHORTED VPQ VRS VTU VPQ + VRS + VTU IS (Measured) IS =

READING

VSUPPLY 10V  60 60 

Calculated value of IS = 0.166 A

Questions to be answered to show understanding of the practical task. (1) What does the ammeter read, if the supply voltage is 5 volts?

................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE (2) What happens to the voltage across the 20 resistor, if the short circuit across AB is replaced with a 40 resistor? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

PRACTICAL TASK 3 THE PARALLEL CIRCUIT

G A + + D.C. SUPPLY 10 VOLTS 

H  100 (2W) +A A -B mA D 1 200 (2W) +C A mA F 2 300 (2W) 3 R2 R3

RANGE  mA R1

+E A mA

1. Connect the circuit as shown, without the meters connected. 2. Set the D.C. supply to 10V using the voltmeter. Switch off. 3. Short out G - H and place the ammeter across A-B. Switch on and note the reading. Switch off. 4. Repeat step (3) with the ammeter connected across C-D and E-F. 5. Short out A-B, C-D and E-F. Reconnect the short circuit on G-H and replace with the ammeter across G-H. Switch on and note the reading. Switch off.

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ADNOC TECHNICAL INSTITUTE 6. KIRCHHOFF’s first law is now proved as IGH = IAB + ICD + IEF (IS) = (I1) + (I2) + (I3)

7. Short out G-H, A-B, C-D and E-F. Switch on. With a voltmeter measure VSUPPLY, VR1, VR2 and VR3. 8. This will show that, in a parallel circuit, the voltage is the same across all loads. RESULTS TABLE OPERATION
AMMETER ACROSS AB AMMETER ACROSS CD AMMETER ACROSS EF

READING
mA mA mA IS = IS = V V V V mA mA

I1 + I2 + I3
AMMETER ACROSS GH

A

VR1 VR2 VR3
VSUPPLY

Questions to be answered to show understanding of the practical task. (1) Calculate the resistance of the three resistors in parallel and find the supply current (IS) for a supply voltage of 10V. This answer should be, within the accuracy of the equipment, the same as the measured IS. ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE (2) Are the measured values for I1, I2 and I3 the same as the following? I1 =
10V 10V 10V , I2 = and I3 = 100 200 300

................................................................................................

PRACTICAL TASK 4 THE SERIES - PARALLEL COMBINATION CIRCUIT
+
+ A  B 10 

A

SUPPLY VOLTAGE 11 VOLTS

20 

30 



1. Connect the circuit as shown, without the ammeter connected. 2. After the instructor has checked the circuit, switch on the power supply. Set the supply and voltage to 11V. Switch off. 3. Connect the ammeter into the circuit. Switch on and note down the reading of the ammeter. Switch off. RESULTS TABLE

VOLTMETER (VOLTS)

AMMETER (mA)

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ADNOC TECHNICAL INSTITUTE Question to be answered to show understanding of the practical task. Calculate the total resistance of the circuit and the supply current (IS) with supply voltage at 11V. The calculated current will be, within the limits of accuracy, the value measured on the meter. ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ PRACTICAL TASK 5 THE WHEATSTONE BRIDGE

+
SWITCH 10 k  SUPPLY VOLTAGE 10 VOLTS R1 A 20 k  R2 DECADE BOX RX



1. Connect the circuit as shown with the switch in the open position. 2. After the instructor has checked the circuit, set the ammeter at its highest range. Close the switch. 3. Adjust the decade box until the ammeter reads as near zero as possible on the lowest range. Note the value of the decade box. Switch off. 4. Calculate the value of RX using the formula RX = R1 multiplied by the decade box value
R2

5. Check your answer by measuring RX on an ohmmeter.

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 6 A.C. AND RMS VALUES

A.C.SUPPLY 50 HZ 6.3 VRMS

100  (2W)

OSCILLOSCOPE

PEAK TO PEAK VALUE

1. Connect a 100 resistor across 6.3 VRMS supply, as shown. 2. Connect an oscilloscope across the resistor and measure the peak to peak value. 3. Divide this value by 2 2 (1.414) to find the RMS value. 4. Connect a DMM set to measure A.C. voltage across the resistor. This shows that, within limits, the device is calibrated in RMS. 5. Connect an ammeter, which must be set to measure A.C. current, in the circuit. It should read VRMS  100, to show it is also calibrated in RMS. 6. Using the time basis scale, show the supply frequency is 50Hz. Remember the frequency = 1  period. Question to be answered to show understanding of the practical task. Why is it not possible to display the workshop socket A.C. waveform on the oscilloscope? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 7 D.C. AND THE CAPACITOR

1M 

+
10 VOLTS D.C. SUPPLY 100 F

+ 

+
DVM V RANGE 0-10 VOLTS D.C





1. Connect the circuit as shown in the diagram. 2. After the instructor has checked the circuit, switch on the supply. Note the reading on the DVM every 10 seconds as the capacitor charges. When the DVM is steady, switch-off the supply. Discharge the capacitor by switching the DMM to the D.C. ampere range. 3. Plot the results obtained on a graph and estimate the RC time of the circuit (time to reach 6.32V).

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ADNOC TECHNICAL INSTITUTE RESULTS TABLE TIME (S) 0 10 20 30 40 50 60 70 80 90 100 110 120 DVM (V)

CALCULATIONS Estimated RC time Calculated RC time QUESTION Why are the estimated and calculated RC times different? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ = = _____________ secs. _____________ secs.

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 8 THE INDUCTOR AND A.C.
mA
FUNCTION GENERATOR SET FOR A SINEWAVE 1V 100 mH

1. Connect the circuit, as shown, with the function generator set at 100 Hz with a 1V output. Write down the reading indicated on the mA meter. 2. Repeat step (1) with a function generator output of 1V for frequencies of 200, 400, 800, 1000, 1200 and 1400 Hz. Note the reading of the mA meter each time. 3. Work out the reactance of the coil at each frequency (divide 1V by mA reading). 4. Plot a graph of reactance against frequency. 5. The graph will show that inductive reactance increases linearly (in a straight line) with frequency.

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ADNOC TECHNICAL INSTITUTE RESULTS TABLE FREQUENCY 100 200 400 800 1000 1200 1400 Supply voltage constant at 1V. Questions answered must show understanding of the practical task. (1) Calculate the reactance of the inductor at 1000 Hz. mA XL (
1 ) mA

................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ (2) Why is it different from the measured value?

................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 9 THE CAPACITOR AND A.C.
mA
FUNCTION GENERATOR SET FOR A SINEWAVE 1V

1 F (non-polarised)

1. Connect the circuit as shown, with the function generator set at 100 Hz with a 1V output. Write down the reading indicated on the mA meter. 2. Repeat step (1) with a function generator output of 1V for frequencies of 200, 400, 800, 1000, 1200 and 1400 Hz. Note the reading of the mA meter each time. 3. Work out the reactance of the capacitor at each frequency (divide 1V by mA reading). 4. Plot a graph of reactance against frequency. 5. The graph will show that capacitive reactance falls exponentially with frequency.

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ADNOC TECHNICAL INSTITUTE RESULTS TABLE FREQUENCY 100 200 400 800 1000 1200 1400 Supply voltage constant at 1V. Questions to be answered to show understanding of the practical task. (1) Calculate the reactance of the capacitor at 1000 Hz. mA XC (
1 ) mA

................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ (2) Why is it different from the measured value?

................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 10 A.C. CURRENT AND VOLTAGE IN AN INDUCTANCE
H 100 mH FUNCTION GENERATOR SET FOR 5V AT 1kHZ A SINEWAVE 20 L OSC TRACE 1

OSC TRACE 2

1. Connect the circuit as shown.

Connect the earth leads of the

oscilloscope (OSC) to the LOW side of the function generator. 2. Adjust the waveforms to approximately the same size and sketch the waveforms shown on the oscillator. 3. The waveforms should show approximately a 90 phase shift between the voltage across the inductor and the current (voltage across the 20  resistor) through the inductor. Question to be answered to show understanding of the practical task. Does the voltage lead the current or the current lead the voltage? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 11 A.C. CURRENT AND VOLTAGE IN A CAPACITANCE
H 0.1 F OSC TRACE 1

FUNCTION GENERATOR SET FOR 5V AT 1kHZ A SINEWAVE 20 L

OSC TRACE 2

1. Connect the circuit as shown.

Connect the earth leads of the

oscilloscope (OSC), to the low side of the function generator. 2. Adjust the waveforms to approximately the same size. waveforms displayed. 3. The waveforms should show approximately a 90 phase shift between the voltage across the capacitor and the current (voltage across the 20 resistor) through the capacitor. Question to be answered to show understanding of the practical task. 1.Does the voltage lead the current or the current lead the voltage? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................ Sketch the

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 12 A.C. AND THE INDUCTOR / CAPACITOR RESISTIVE CIRCUIT INTRODUCTION The previous two tasks (10 and 11) showed the phase shift between the current and voltage waveform when a capacitor or inductor is supplied with A.C. This task will show how the phase shift between the current and the voltage can be adjusted. This is done using an inductor / capacitor with a resistor in a series circuit.

H 100 mH FUNCTION GENERATOR SET FOR 5V AT 1kHZ A SINEWAVE 1 k L OSC TRACE 1

OSC TRACE 2

1. Connect the circuit as shown. Sketch the two waveforms shown on the oscilloscope. 2. Change the frequency to 500 Hz. Sketch the waveforms. 3. Change the frequency to 2000 Hz. Sketch the waveforms. 4. Replace the 100 mH inductor with a 0.1F capacitor. 5. Repeat steps (1) through (3) and sketch the waveforms. Questions to be answered to show understanding of the practical task. (1) Work out the phase shift at the various frequencies from the sketches you have made. ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE (2) Do these sketches show that the inductive reactance goes up with frequency and the capacitive reactance goes down with frequency? ................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE PRACTICAL TASK 13 RESONANCE SERIES
H

FUNCTION GENERATOR SET FOR A SINEWAVE 5V 1 k L

0.1 F 100 mH DVM

1. Connect the circuit as shown. 2. Set the function generator to 200 Hz and note the reading on the DVM. 3. Repeat step (2) for frequencies of 400, 600, 800, 1000, 1200, 1400. 1800, 2000 and 2200 Hz. 4. Adjust the frequency on the function generator to obtain the largest reading on the DVM. Note the frequency. 5. Draw a graph of DVM reading against frequency. 6. The graph should show the circuit resonates. voltage (current) at one frequency. Questions to be answered to show understanding of the practical task. (1) Calculate the resonant frequency from the theory f =
1 2  LC

It has a maximum

................................................................................................ ................................................................................................ ................................................................................................ (2) Does your calculation agree with the result obtained from step (4)?

................................................................................................
…………………………………………………………………………………...

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ADNOC TECHNICAL INSTITUTE PARALLEL
H 0.1 F 100 mH

FUNCTION GENERATOR SET FOR A SINEWAVE

1 k L

DVM

1. Connect the circuit as shown. 2. Set the function generator to 200 Hz. Note this reading on the DVM. 3. Repeat step (2) for frequencies of 400, 600, 800, 1000, 1200, 1400. 1800, 2000 and 2200 Hz. 4. Adjust the frequency on the function generator to obtain the smallest reading on the DVM. Note the frequency. 5. Draw a graph of the DVM reading against the frequency. 6. The graph should show the circuit resonates. voltage (current) at one frequency. Questions to be answered to show understanding of the practical task. (1) Calculate the resonant frequency for the theory f =
1 2  LC

It has a minimum

................................................................................................ ................................................................................................ ................................................................................................ (2) Does your calculation agree with the result obtained from step (3)?

................................................................................................ ................................................................................................ ................................................................................................ ................................................................................................

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ADNOC TECHNICAL INSTITUTE RESISTANCE COLOUR CODES Method 1 COLOUR BANDING
LARGER SPACE

TOLERANCE 1
ST

NUMBER

2ND NUMBER

MULTIPLIER

The diagram shows a colour coded resistor. The colour code is there to show you the resistance of the resistor. Reading from left to right, the first and seconds bands indicate a number, (eg. if the first colour band is 4 and the second colour band is 7 then the number is 47). The third band is the multiplier in power form, (eg. 103). The fourth band indicates the tolerance of the resistor (eg.  5%). The numbers to match the colours are internationally fixed and are given below.

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COLOUR Black Brown Red Orange Yellow Green Blue Violet Grey White Gold Silver

NUMBER (BAND 1&2) 0 1 2 3 4 5 6 7 8 9 (100) (101) (102) (103) (104) (105) (106) (107) (108) (109) (10-1) (10-2)

MULTIPLIER (BAND 3) 1 10 100 1 000 10 000 100 000 1 000 000 10 000 000 100 000 000 1 000 000 000 0.1 0.01

TOLERANCE (BAND 4)

 1%  2%

 5%  10%

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ADNOC TECHNICAL INSTITUTE Example 1
RED VIOLET GOLD

GREEN

The example has the bands red, violet, green and gold. This means 27 x 100 000 (105) = 2.7 M Tolerance  5% Example 2
BLACK GREEN GOLD RED

The example has the bands black, green, gold and red. This means 05 x 0.1 = 0.5 Tolerance  2% Example 3
RED BLACK BLACK BROWN

The example has the bands red, black, black and brown. This means 20 x 1 = 20 Tolerance  1%

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ADNOC TECHNICAL INSTITUTE Method 2 The newer types of resistor have the value and tolerance printed on them. These use letters to show the powers. R = 1 K = 1000 M = 1 000 000 Examples 100 R = 100 1R1 = 1.1 1K5 = 1 500 4M7 = 4 700 000 This method of numbering resistors is now used on circuit diagrams and in catalogues when ordering resistors. Note: Various colour codes for capacitors have been devised. However none of these are widely accepted so they are not worth learning. Tolerance: This is the range over which a component is allowed to vary from its stated value. The closer the tolerance the more accurate the component. However, the closer the tolerance the higher the cost. Electrical/electronic circuits are designed so that close tolerance components are only used when it is necessary for correct operation. Example Find the acceptable range of values for a 1K resistor with a tolerance of  5%. 5% of 1 000 = 50  Acceptable range will be 1 000  50  or 950  to 1 050 

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ADNOC TECHNICAL INSTITUTE Power Rating. When an electric current is passed through a resistor, energy is dissipated (used) in the form of heat. So, resistors are made according to how much heat (power) they can take without burning out. This is called the power rating. The power rating of a resistor is not usually printed on the resistor. The manufacturer's catalogue will tell you the maximum power it can handle. The construction of resistors depends on their power rating. There are two basic kinds. (1) Film Resistors
END CAP GROOVES CONNECTING LEAD

PLASTIC COATED INSULATOR

CERAMIC CYLINDER

Figure PT-1 Film Resistor Figure PT-1 shows a film resistor used in electronics. It is made by

putting a thin coating (a film) of a carbon or metal compound onto a ceramic cylinder. The resistivity of the coating compound is varied to give the necessary resistance value. The resistance can be made more accurate by cutting grooves in the film. The grooves change the area and thus the resistance. The connections to the resistor are made by brass or nickel caps and copper connecting leads. The device is coated with a plastic insulator and painted with the colour code. These resistors are made in various values from about 1 to 10M with a power rating to about 2W.

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ADNOC TECHNICAL INSTITUTE (2) Wire Wound These resistors are made for high power applications. An instrument

technician will only see these types in power amplifiers driving field devices (e.g. relays, solenoid valves, etc.) however, they are often used in electrical work.
INSULATION

CERAMIC CYLINDER

WOUND RESISTANC E WIRE

Figure PT-2 Wire Wound Resistor Figure PT-2 shows a wire wound resistor. It consists of a ceramic cylinder with a resistance wire wound around it. The resistance value depends on the resistivity of the wire and the number of turns. These resistors can be very accurate. They are used as standard resistors. The insulation on the device depends on what the device will be used for. Very high power resistors which need to dissipate kilowatts usually have no insulation. They lose the heat by radiating it outwards like the sun. Electronic power resistors are usually insulated with what is called "vitreous enamel". This provides good insulation with good heat radiation properties. The wire wound resistor usually has its resistance value and its tolerance written on the device (no colour code). maximum value of about 100 k. Wire wound resistors are only produced in the lower resistance ranges with a

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ADNOC TECHNICAL INSTITUTE The power ratings produced for electronics vary from about 2.5W to 50W. However, some electrical systems may use resistors with power ratings of many kilowatts. Note: The latest type of resistors come in what are called "chips". These are film resistors. They are constructed on a ceramic chip. There are connecting pads on the bottom so it can be surface mounted on a printed circuit board. The "chips" come from the factory stuck on a tape. They are removed one at a time when they are needed. Figure PT-3 shows a typical chip resistor.

2MM

1.25mm CONNECTOR PADS

Figure PT-3 Chip Resistor

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DOCUMENT INFO
Description: Instrumentation Course