Course: EEE251: Measurement and

Instrumentation
Lecture-3: Measure Elec. Quantities
Text Book: (1) Measurement and Instrumentation by A. K. Sawhney.
Reference Books:
(2) Electronic Instrumentation and measurement
Techniques by W.D. Cooper.
(3) Measurement & Instrumentation – Harries K. Forrest.
C.T. by--
Dr. Mohammad Asaduzzaman KHAN
Room # 305

Department of EEE, BSMRSTU,

arzu1013@Hotmail.com.
 SYLLABUS
EEE251 Measurement and Instrumentation
Prerequisite: EEE211 AVO-meter stands for Ampere, Volt and Ohm meter.
3 Credits, 3 hours/week
Introduction:ch1, 2, 3
Applications, functional elements of a measurement system and classification of instruments (Ammeter,
Voltmeter, wattmeter, AVO meter, Energy meter, Ampere-hour meter, CRO).
Measurement of Electrical Quantities: ch8, 9
Current and voltage, power and energy measurement. Current and voltage, power and energy measurement
Current and potential transformer.
Transducers: ch25
Mechanical, electrical and optical transducers.
Measurement of Non-Electrical Quantities: ch29
Temperature, pressure, flow, level, strain, force and torque, earthquake, speed, frequency, phase difference.
Basic Elements of DC and AC Signal Conditioning: ch26
Instrumentation amplifier, noise and source of noise, noise elimination compensation, function generation and
linearization, A/D and D/A converters, sample and hold circuits.
Data Transmission and Telemetry: ch27, 28
Methods of data transmission, DC/AC telemetry system and digital data transmission. Recording and display
devices. Data acquisition system and microprocessor applications in instrumentation.
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 SYLLABUS
Books recommended:
1. Measurement & Instrumentation – A. K. Sawhney
2. Measurement & Instrumentation – Harries K. Forrest

EEE252 Sessional Based on EEE251.

0.75 Credits, 3/2 hours/week
Laboratory experiments based on theory and concepts learnt in EEE251.

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Measuring Meters

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Measuring Meters

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Measuring Meters

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Measuring Meters-Ampere-hour meter
Ampere (Amp) hour meter is a solid state measuring device, a
similar concept to that of a water meter, which is used to
calculate the amount of electricity charge used by multiplying
the flow rate of electrons by the amount of time electrons flow
through the wire.

This eliminates the need of calibrated shunt leads, which

happen to be an expensive and rather a tedious process.
The computer controlled ampere hour meter provides a simple
and cost effective method of tracking current and time either in
ampere-hours or ampere-minutes during plating or anodizing
operations, which turns out to be an escapade of sorts.

As told, the concept of an amp-hour meter is similar in concept

to a water meter, i.e. a water meter determines the amount of
water used by calculating the flow rate of the water through a
pipe and then multiplying.

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 Measuring Meters-Ampere-hour meter
Majority of the devices are based on the structure quite similar to that of an ammeter, an electronic
instrument which is used to measure current. But going by this, it will result in quite a simple formation
which will be solely giving out the status or measurement of the current being used, then multiply the
amount of time (in ours) it is at the level of current.
Now it is very important in such a structure to restart the timings every time the current reading
changes, moreover for each change in current level one should have the time in hours that corresponds
to the time the current was at the specific level. Post all this, multiplying the current and time together for
each current level and eventually adding up the sum of these calculations together.
This is the number of amp-hours, now that surely is a task in hand. To sum it up anAmp Hour
Meter incorporates timing, multiplication and summing circuits in addition to an ammeter circuit.
Different ampere hour meters are designed to measure direct current, the type of current found in
battery powered circuits; alternating current, the type of current generated from electric wall sockets; or
pulsed currents, the type of current found in data communications wires. This explains how widely and
important its use is.

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Measuring Meters—AVO meter
AVO meter stands for A – ampere, V – volt, O – ohm meter. It is also known as a multimeter. Avometer
or multimeter is a tester (instrument) that is used to measure electric current (both AC and DC), the
potential difference between two points in a circuit, and also measures resistance in a circuit.

FUNCTION of AVO meter:

•It is a very important instrument for measuring volts, ohms, and amperes quickly and easily,
•As well as locating faults in electric or electronic circuits.
Multimeter basically consists of sensitive moving coil galvanometer which can be converted into
•Multirange ammeter by connecting a current measuring circuit
•Multirange voltmeter by connecting a voltage measuring circuit
•Multirange ohmmeter by connecting a resistance measuring circuit.

A switch called function switch is used. The function switch is the function selector switch that
connects the galvanometer with the relevant measuring circuit i.e., current, voltage or resistance.

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 Measuring Meters—AVO meter
This is multirange voltmeter. This part consists of a number of resistances each of which is connected
with the moving coil of the galvanometer in series. It is connected with the help of rang switch.
The value of each resistance depends upon the range voltmeter. The series resistances are called
multipliers. It can measure AC voltage but for this purpose, AC is first converted into DC.

It is multirange ammeter. This part consists of the number of low resistances

connected with a galvanometer in the parallel circuit. These resistances
depend upon the range of the ammeter. This circuit also has a range
selection switch SR used to select a particular range.
It is multirange ohmmeter. This part consists of a battery of emf Vo and a
variable resistance Rs connected with a galvanometer of resistance Rg in
series. When the function switch is switched to position X3, the circuit is
connected to the X and Y terminals of the AVOmeter. Before measuring
the unknown resistance, it is first zeroed which means that we short
circuit the terminals X and Y of the Avometer and adjust Rs to produce
full-scale deflection.

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 Measuring Meters—AVO meter
Based on the working principle, there are two types of AVO meter:
AVO meter analog
AVO Meter utilizing the needle as a tip analog range. To get the measurement results, they ought to be read
by range or divisions. The precision of the dimension outcomes of the AVO Meter analog is restricted by the
size of the scale pointer, the vibration of the pointer, the accuracy of printing axle, zero calibration, number of
ranges of scale. In measurements making use of AVO Meter Analog, dimension errors can take place
because of mistakes in monitoring (parallax).
AVO digital meter
Digital multimeter includes an electronic counter and also
LCD present instead of relocating needle and ruler. Digital
multimeters, which are a little a lot more expensive than
analog multimeters, have come to be an extensively made
use of multimeter type thanks to their simple reading as well
as high accuracy dimension.
The important features are:
•More accuracy and precision
•Easy to operate
•Easy to read
•Removes the reading error
•Shows digital values with decimal points, polarity, and units
of A, V, and Ω. 27
Measuring Meters—AVO meter

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Measuring Meters—AVO meter

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Measuring Meters—AVO meter

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Measuring Meters—CRO

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Measuring Meters--CRO

Fig.--BASIC CRO CIRCUIT 32

Measuring Meters--CRO

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Measuring Meters--CRO

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Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 35

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 36

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 37

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 38

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 39

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 40

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 41

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 42

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 43

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 44

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 45

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 46

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 47

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 48

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 49

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 50

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 51

Measurement of Power and Energy

The source of these information is Text Book (4th Edition). 52

AC Meter

The source of these information is Text Book (4th Edition). 53

AC Meter

The source of these information is Text Book (4th Edition). 54

AC Meter

The source of these information is Text Book (4th Edition). 55

AC Meter

The source of these information is Text Book (4th Edition). 56

AC Meter

The source of these information is Text Book (4th Edition). 57

AC Meter

The source of these information is Text Book (4th Edition). 58

AC Meter

The source of these information is Text Book (4th Edition). 59

AC Meter

The source of these information is Text Book (4th Edition). 60

AC Meter

The source of these information is Text Book (4th Edition). 61

AC Meter

The source of these information is Text Book (4th Edition). 62

 Instrument Transformer
Current transformers, along with voltage or potential transformers, are instrument
transformers. Instrument transformers scale the large values of voltage or current to
small, standardized values that are easy to handle for instruments and protective relays.

Basic operation of
current transformer
Many digital clamp meters utilize a
current transformer for
measuring alternating current(AC).
SF6 110 kV current transformer
TGFM series, Russia

A CT for operation
on a 110 kV grid

The source of these information INTERNET 63

Instrument Transformer

The source of these information is Text Book (4th Edition). 64

Instrument Transformer

The source of these information is Text Book (4th Edition). 65

Why Instrument Transformer?

The source of these information is Text Book (4th Edition). 66

Why Instrument Transformer?

The source of these information is Text Book (4th Edition). 67

Instrument Transformer Ratio

The source of these information is Text Book (4th Edition). 68

Instrument Transformer Ratio
 Instrument Transformer Burden
• The secondary load of a current transformer is termed the "burden" to distinguish it from
the primary load.

• The burden in a CT metering electrical network is largely resistive impedance presented to its
secondary winding. Typical burden ratings for IEC CTs are 1.5 VA, 3 VA, 5 VA, 10 VA, 15 VA, 20 VA,
30 VA, 45 VA and 60 VA. ANSI/IEEE burden ratings are B-0.1, B-0.2, B-0.5, B-1.0, B-2.0 and B-4.0.

• This means a CT with a burden rating of B-0.2 will maintain its stated accuracy with up to
0.2 Ω on the secondary circuit.
• Items that contribute to the burden of a current measurement circuit are switch-blocks, meters and
intermediate conductors.
• The most common cause of excess burden impedance is the conductor between the meter and the
CT.
• When substation meters are located far from the meter cabinets, the excessive length of cable
creates a large resistance.
• This problem can be reduced by using thicker cables and CTs with lower secondary currents (1 A),
both of which will produce less voltage drop between the CT and its metering devices. 70
Instrument Transformer Burden

The source of these information is Text Book (4th Edition). 71

Instrument Transformer ---C.T.

The source of these information is Text Book (4th Edition). 72

Instrument Transformer

The source of these information is Text Book (4th Edition). 73

Instrument Transformer

The source of these information is Text Book (4th Edition). 74

Instrument Transformer

The source of these information is Text Book (4th Edition). 75

Instrument Transformer

The source of these information is Text Book (4th Edition). 76

Instrument Transformer

The source of these information is Text Book (4th Edition). 77

Instrument Transformer

The source of these information is Text Book (4th Edition). 78

Instrument Transformer

The source of these information is Text Book (4th Edition). 79

Instrument Transformer

The source of these information is Text Book (4th Edition). 80

Substation
The power system is a constituent of power generation,
transmission and distribution systems. For all the power
system operations, substations are required for their
course of action.

Based on the application of substations, they are

classified into different types: Generation substation,
Indoor substation, Outdoor substation, Pole mounted
substation, Switching substation, Transmission substation,
Converter substation and Distribution substation.

Substation

The source of these information is Text Book (4th Edition). 81

Substation

The source of these information is Text Book (4th Edition). 82

 Instrumentation of a Substation
The substation is an assembly of the following major electrical equipment:

•Electrical Power transformers

•Instrument transformers
•Conductors& Insulators
•Isolators
•Bus bars
•Lightning arresters
•Circuit breakers
•Relays
•Capacitor banks and miscellaneous equipment

The source of these information is Text Book (4th Edition). 83

 Instrumentation of Substation
Electrical Power Transformer
A static electrical machine used for transforming power from one circuit to another circuit without changing
frequency is termed as Power transformer. The transformers are generally used to step down or step up the
voltage levels of a system for transmission and generation purpose. These transformers are classified into
different types based on their design, utilization purpose, installation methods, and so on.

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 Instrumentation of Substation
Instrument Transformers:
Instrument transformers
The current and voltage transformers are together called as the Instrument transformers.

Instrument Transformer

• Current Transformer
Current transformer is used for the measurement of the alternating
current by taking samples of the higher currents of the system. These
reduced samples are in accurate proportions with the actual high
currents of the system. These are used for installation and
maintenance of the current relays in substations for protection
purpose which are normally have low-current ratings for their
operation.

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Current Transformer
• Potential Transformer
Potential transformer is quite similar to the current transformer, but it is used for taking samples of high
voltages of a system for providing low-voltage to the relays of protection system and also to the low-rating
meters for voltage measurement. From this low-voltage measurement, the actual system’s high voltage can be
calculated without measuring high voltages directly to avoid the cost of the measurement system.

Voltage Transformer
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 Instrumentation of Substation
Bus Bar
The bus bar is a very important component in an electrical substation. It is a kind of current carrying conductor
where many connections are made. In other terms, it can be defined as it is one type of electrical connection
where the incoming current and outgoing current take place.

Busbar
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 END

The source of these information is Text Book (4th Edition). 88