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ST. PETER’S ENGINEERING COLLEGE
(Approved by AICTE, Affiliated to JNTU Hyderabad)
Opp: AP Forest Academy, Dhullapally, Near Kompally, Secunderabad - 500010
DEPARTMENT
OF
ELECTRICAL AND ELECTRONICS ENGINEERING
Name of the course : Electrical measurements and Instrumentation lab
Name of the Dept. : ELECTRICAL AND ELECTRONICS ENGINEERING
Name of the Faculty : K.V.V.Nagababu, Assistant Professor
Class : III Year B.Tech. EEE, I – Sem
Academic year : 2018-19
SPEC/ECE/UG/CF-0403/2017 – 18
CERTIFICATE OF AUTHENTICATION
This is to certify that K.V.V.Nagababu,Assistant professor of Electrical and Electronics
Engineering Department has prepared the course material for Electrical Measurements and
Instrumentation lab of Jawaharlal Nehru Technological University, Hyderabad for the
academic year 2018 –19. The contents of this course/teaching module have not been reproduced
elsewhere in any books or journals.
This is the sole property of St. Peter’s Engineering College, Hyderabad to be referred by
staff and students.
Name of the Faculty: K.V.V.Nagababu
HOD
(EEE department)
Signature
INSTITUTE VISION
Our vision is to promote quality education accessible to all sections of the Society without
any discrimination of caste, creed, color, sex and religion and help students discover their true
potential.
INSTITUTE MISSION
M1.To provide integrated, continuous and wholesome development of students by
equipping them with knowledge and skills, social values and ethics, scientific attitude and
orientations for lifelong education and mold them into useful citizens of the society.
M2. To create an environment conductive to inhibiting theirs total involvement and participation
of the students, faculty, staff and management. In making the institution into a center of
excellence imparting quality technical education and also arms the students with the competence
to be at the forefront of cutting edge technology and entrepreneurship in highly competitive
global market.
Department of Electrical and Electronics Engineering
DEPARTMENT VISION
To Evolve the department as a centre of excellence in Electrical and Electronics Engineering
education in the country, to train students in contemporary technologies to meet the needs of
global industry and to develop them into skilful engineers imbued with knowledge of core as
well as inter-disciplinary domains, human values and professional ethics.
DEPARTMENT MISSION
•Impart quality education to the students to enter a dynamic and rapidly changing field with
career opportunities in Electrical Power System, Electronics and Software Professional.
•Electrical and Electronics Engineering Department was found with a threefold mission in
teaching, research, and public service. Based on that foundation, the mission of the Department,
in all major fields of Electrical and Electronics Engineering, is to instill in students the attitudes,
values, vision, and training that will prepare them to learn and to lead continuously for life-time.
•Develop the ability and passion to work creatively, effectively and wisely for the benefit of
society.
•Generate new knowledge for the betterment of humankind and to utilize it universally.
•Generate realistic and innovative solutions for the current needs and future technological needs
and to play a leading role to form the van of social and scientific progress and to provide special
services where there are needs that the department is uniquely qualified to meet.
•Other than the Academic curriculum, the department also engages in regular Industrial Visits
and In-plant training for students to gain industrial exposure and practical knowledge.
Department of Electrical and Electronics Engineering
Program Educational Objectives (PEOs):
1. PEO1: To provide a solid foundation in Mathematics, Science, Electrical, Electronics and allied
engineering, capable of analyzing, design and development of systems for Energy Generation,
Transmission, Distribution, Operation and Control.
2. PEO2: To prepare the student for a successful career in industry/Technical profession and undertake
post-graduation studies, research and lifelong learning.
3. PEO3: To prepare the student to fulfill the needs of society in solving technical problems using
engineering principles, tools and practices.
4. PEO4: To equip student with the knowledge of modern simulation tools to solve complex
Engineering problems.
5. PEO5: To inculcate professional and ethical attitudes, team work skills, leadership qualities and
good oral and written communication skills.
Program Outcomes (POs):
1. ENGINEERING KNOWLEDGE: Apply the knowledge of mathematics, science,
engineering fundamentals, and an engineering specialization to the solution of complex
engineering problems.
2. PROBLEM ANALYSIS:Identify, formulate, research literature, and analyze complex
engineering problems reaching substantiated conclusions using first principles of
mathematics, natural sciences, and engineering sciences.
3. DESIGN/DEVELOPMENT OF SOLUTIONS:Design solutions for complex
engineering problems and design system components or processes that meet the specified
needs with appropriate consideration for the public health and safety, and the cultural,
societal, and environmental considerations.
4. CONDUCT INVESTIGATIONS OF COMPLEX PROBLEMS:Use research-based
knowledge and research methods including design of experiments, analysis and
interpretation of data, and synthesis of the information to provide valid conclusions.
5. MODERN TOOL USAGE:Create, select, and apply appropriate techniques, resources,
and modern engineering and IT tools including prediction and modelling to complex
engineering activities with an understanding of the limitations.
6. THE ENGINEER AND SOCIETY:Apply reasoning informed by the contextual
knowledge to assess societal, health, safety, legal and cultural issues and the consequent
responsibilities relevant to the professional engineering practice.
7. ENVIRONMENT AND SUSTAINABILITY:Understand the impact of the professional
engineering solutions in societal and environmental contexts, and demonstrate the
knowledge of, and need for sustainable development.
8. ETHICS:Apply ethical principles and commit to professional ethics and responsibilities
and norms of the engineering practice.
9. INDIVIDUAL AND TEAM WORK:Function effectively as an individual, and as a
member or leader in diverse teams, and in multidisciplinary settings.
10. COMMUNICATION:Communicate effectively on complex engineering activities with
the engineering community and with society at large, such as, being able to comprehend
and write effective reports and design documentation, make effective presentations, give
and receive clear instructions.
11. PROJECT MANAGEMENT AND FINANCE:Demonstrate knowledge and
understanding of the engineering and management principles and apply these to one’s
own work, as a member and leader in a team, to manage projects and in multidisciplinary
environments.
12. LIFE-LONG LEARNING:Recognize the need for, and have the preparation and ability
to engage in independent and life-long learning in the broadest context of technological
change.
Programme specific outcomes (PSOs):
PSO 1. An ability to endeavor the public and private sector, national level examination and
interviews successfully.
PSO2. An ability to design solutions for Electrical transmission and distribution systems.
PSO3. An ability to undertake research in power electronics and power systems.
Department of Electrical and Electronics Engineering
Name of the Faculty: K.V.V. Nagababu Class: III EEE-I SEM
Course Name: EMI Lab Academic Year: 2018-19
Course Objectives:
To calibrate LPF Watt Meter, energy meter, P. F Meter using electro dynamo meter type
instrument as the standard instrument
To determine unknown inductance, resistance, capacitance by performing experiments on
D.C Bridges & A. C Bridges
To determine three phase active & reactive powers using single wattmeter method practically
To determine the ratio and phase angle errors of current transformer and
potential transformer.
Course Outcomes:
1. To choose instruments
2. Test any instrument
3. Find the accuracy of any instrument by performing experiment
4. Calibrate PMMC instrument using D.C potentiometer
List of Experiments:
Expt No Name of the experiment COs Mapped PO/PSO
1 Calibration and Testing of single phase energy Meter.
CO 3, CO 2 PO6
2 Calibration of dynamometer power factor meter.
CO 4 PO4
3 PMMC ammeter and PMMC voltmeter.
CO 2, CO 4 PO2
5 Dielectric oil testing using H.T. testing Kit.
CO 2 PO4
6 Schering bridge & Anderson bridge.
CO 1, CO 3 PO3
7 Measurement of 3 – Phase reactive power with single-
phase wattmeter.
CO 2, CO 4 PO2
8 Measurement of displacement with the help of LVDT.
CO 4, CO2 PO4
9 Calibration LPF wattmeter – by Phantom testing.
CO2, CO 4 PO2
10 Measurement of 3-phase power with single watt meter
and two CTs.
CO 2, CO3 PO3
11 Resistance strain gauge – strain measurements and
Calibration.
CO 2 PO4
List of Additional Experiments:
Expt
No Name of the experiment CO Mapped
PO/PSO
1 C.T. testing using mutual Inductor – Measurement of %
ratio error and phase angle of given CT by Null method.
CO 1, CO 2 PO3
2 PT testing by comparison – V. G. as Null detector –
Measurement of % ratio error and phase angle of the
given PT
CO 2, CO 4
Po3
3 Crompton D.C. Potentiometer
CO 2, CO 4 PO2
4 Transformer turns ratio measurement using AC bridges.
CO 1, CO 2 PO5
5 Measurement of % ratio error and phase angle of given
CT by comparison.
CO 2, CO 3,
CO 4
PO2
Faculty in-charge
Department of Electrical and Electronics Engineering
Name of the Faculty: K.V.V.Nagababu Class: III EEE-I SEM
Course Name: EMI LAB Academic Year: 2018-19
INDIVIDUAL FACULTY TIME-TABLE
Day/
Hou
r
1
(9.00A
M-
9.50A
M)
2
(9.50AM-
10.40AM
)
3
(10.40A
–
11.30A
M)
4
(11.30
AM-
12.20
PM)
LUNC
H
5
(1.00P
M-
1.50P
M)
6
(1.50P
M-
2.40
PM)
7
(2.40P
M-
3.30P
M)
8
(3.30P
M-
4.20P
M)
MO
N
1 Batch
TU
E
WE
D
TH
U
FRI
SAT 2 Batch
FACULTY SIGN TIME TABLE I/C
HOD
Lab External Exam Questions:
Exp No, Question
1 How to Calibration and Test single phase energy
2 How Calibration dynamometer power factor meter.
3 Kelvin’s double Bridge – Measurement of resistance – Determination of
Tolerance.
4 How do you test the dielectric oil strength using H.T. testing Kit.
5 Find unkown capacitance and inductance for the given capacitor and inductor
6 Measure the 3 – Phase reactive power with single-phase wattmeter.
7 Measure of displacement with the help of LVDT.
8 Calibrate LPF wattmeter – by Phantom testing.
9 How do you measure of 3-phase power with single watt meter and two CTs.
10 How do you test C.T. testing using mutual Inductor – Measure % ratio error and
phase angle of given CT by Null method.
11 PT testing by comparison – V. G. as Null detector – Measurement of % ratio
error and phase angle of the given PT
12 Resistance strain gauge – strain measurements and Calibration.
Faculty in-charge
B-Tech III Year I Sem EMI Lab External Exam Time Table for the Year 2018-2019
DATE:
BRANCH NAME OF THE
LABORATORY
NO. OF
STUDENTS REG. NO.
DATE OF
EXAM EXTERNAL EXAMINORS TIMINGS
EMI
EMI
EMI
EMI
COORDINATOR
HOD
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EE505PC: ELECTRICAL MEASUREMENTS & INSTRUMENTATION LAB
LAB SCHEDULE
BATCH/
WEEK
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11
W1 E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E1
W2 E2 E3 E4 E5 E6 E7 E8 E9 E10 E1 E2
W3 E3 E4 E5 E6 E7 E8 E9 E10 E1 E2 E3
W4 E4 E5 E6 E7 E8 E9 E10 E1 E2 E3 E4
W5 E5 E6 E7 E8 E9 E10 E1 E2 E3 E4 E5
W6 E6 E7 E8 E9 E10 E1 E2 E3 E4 E5 E6
W7 E7 E8 E9 E10 E1 E2 E3 E4 E5 E6 E7
W8 E8 E9 E10 E1 E2 E3 E4 E5 E6 E7 E8
W9 E9 E10 E1 E2 E3 E4 E5 E6 E7 E8 E9
W10 E10 E1 E2 E3 E4 E5 E6 E7 E8 E9 E10
W11 E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E1
W12 E2 E3 E4 E5 E6 E7 E8 E9 E10 E1 E2
BATCH ROLL NO.(MONDAY) ROLL NO.(SATURDAY)
B1 16Bk1A0201,202,203 16Bk1A0228,229,230
B2 16Bk1A0204,205,206 16Bk1A0231,233,234
B3 16Bk1A0207,208,209 16Bk1A0235,236,237
B4 16Bk1A0210,211,212 16Bk1A0238,239,240
B5 16Bk1A0213,215,216 16Bk1A0241,242,243
B6 16Bk1A0217,218,220 16Bk1A0244,245,246
B7 16Bk1A0221,222,223 16Bk1A0247,248,249
B8 16Bk1A0224,226,227 16Bk1A0250,17BK5A0211,212
B9 17BK5A0201,202,203 17BK5A0214,215,216
B10 17BK5A0204,205,206 17BK5A0217,218,219
B11 17BK5A0207,208,209,210 17BK5A0220,221,222
MEASUREMENTS AND INSTRUMENTATION LAB
List of Major Equipment
(above Rs.10,000)
As on
S. No. Name of the Equipments Unit Cost Quantity
1 HT Oil testing training kit 1
2 CT and PT testing kit
3 Anderson and Schering bridge
4 Energy meter with auto transformer
Lab Incharge
List of Working Models
Academic Year: 2018-19, Semester: Odd
Laboratory Name: EMI Lab Room No.:
S.NO. PROJECT TYPE NAME OF THE
STUDENT
UNIVERSITY
ROLL NO
Faculty-in-charge
HOD
Department of Electrical & Electronics Engineering
EMI Lab
Code of conduct for the laboratory
All students must observe the Dress code while in the laboratory
Sandals or open-toed shoes are NOT allowed
Foods, drinks and smoking are NOT allowed
All bags most be left at the indicated place
The lab timetable must be strictly followed
Be PUNCTUAL for your laboratory session
Experiment must be completed within the given time
Noise must be kept to a minimum
Workspace must be kept clean and tidy at all time
Handle all apparatus with care
All students are liable for any damage to equipment due to their own negligence
All equipment, apparatus, tools and components must be RETURNED to their original
place after use
Students are strictly PROHIBITED from taking out any items from the laboratory
Students are NOT allowed to work alone in the laboratory without the lab supervisor
Report immediately to the lab supervisor if any injury occurred
BEFORE LEAVING LAB:
Place the stools under the lab bench
Turn off the power to all instruments
Turn off the main power switch to the lab bench
Please check the laboratory notice board regularly for updates
Lab Incharge
EMI LAB LAYOUT – Area in Sq.M
Exp. No. :
Date :
1. CALIBRATION AND TESTING OF
66” ft
64” ft
Lab in-charge
Area : 4,224” sqft
Lab capacity : 36 Students
SINGLE PHASE ENERGY METER
AIM: To calibrate the given energy meter using a calibrated wattmeter.
APPARATUS:
1. Variac,single phase, 10 A
2. Voltmeter, 300 V AC
3. Ammeter, 0-10A, AC
4. Rheostat,
5. Wattmeter, LPF, 300V, 10A
6. Single phase energy meter
CIRCUIT DIAGRAM:
PROCEDURE:
Keep the Autotransformer at zero position.
Make connections as per the Circuit diagram shown below.
Switch on the 230 VAC, 50 Hz. power supply.
Increase the input voltage gradually by rotating the Auto transformer in clockwise
direction.
Adjust the load rheostat so that sufficient current flows in the circuit. Please note that the
current should be less then 4A.
Note down the Voltmeter, Ammeter, Wattmeter and power factor meter readings for
different voltages as per the tabular column.
Note down the time (by using stop watch) for rotating the disc of the Energy Meter for 10
times.
Find out the percentage error by using above equations.
CALCULATIONS:
Energy recorded by meter under test = .kWhKx
Rx
Energy computed from the readings of the indicating instrument = .tXkW
Where RX = number of revolutions made by disc of meter under test.
KX = number of revolutions per kWh for meter under test,
kW = power in kilowatt as computed from readings f
indicating instruments
t = time in hours.
Percentage Error = 100)/
tkW
tkWKxRx
Before conducting any of these tests on a watt hour meter its potential circuit must be connected
to the supply for one hour in order to enable the self heating of the potential coil to stabilize.
TABULAR COLUMN:
Si.
No.
Voltage
(V)
Current
(I)
R = No of
revolutions
of the disc
Time
(t) in
hours
Energy meter
reading in
KWh= No.
revolution
(R)/meter
constant (K)
Wattmeter
Reading in
kW × t
%
Error
RESULT:
VIVA QUESTIONS:
1. What is meter constant?
2. What is the principle of induction type instrument?
3. What is the function of maximum demand indicator in industrial metering?
4. What is the function of LAG adjustment device?
5. What is phomton loading?
6. What is creeping of energy meter?
7. What is the function of tri vector meter in industrial metering?
8. What is the function of copper bands in the construction of energy meter.
Exp. No. :
Date :
2. CALIBRATION OF DYNAMOMETER TYPE POWER
FACTOR METER
AIM: To calibrate a given single phase power factor meter
APPARATUS:
1. Variac, single phase,10A
2. Voltmeter, 300V AC
3. Ammeter, 0-10A, AC
4. Rheostat
5. Wattmeter, LPF, 300V, 10A
6. Dynamometer type power factor meter
CIRCUIT DIAGRAM:
PROCEDURE:
1. Keep the Auto transformer at zero position.
2. Make connections as per the Circuit diagram shown below.
3. Switch on the 230 VAC, 50 Hz. power supply.
4. Increase the input voltage gradually by rotating the Auto transformer in clockwise
direction.
5. Adjust the load rheostat so that sufficient current flows in the circuit. Please note that the
current should be less then 4A.
6. Note down the Voltmeter, Ammeter, Wattmeter and power factor meter readings for
different voltages as per the tabular column.
7. Find out the percentage error by using above equations.
CALCULATIONS:
The error made by the Power factor meter can be calculated by nothing down the readings
various meters and error can be calculated by using
Actual reading = Power factor meter reading
Theoretical reading Cos Φ = P /VI
Since percentage of error = 100XreadinglTheiretica
readinglTheoreticareadingActual
TABULAR COLUMN:
S. No. V AC I AC Wattmeter
reading
Power Factor meter
Reading % Error
RESULT:
VIVA QUESTIONS:
1. Define power factor?
2. What are the different types of power factor meters?
3. Why there is no control in torque in electro dynamo power meter?
4. What is torque expression for electro dynamo meter type power factor meter?
5. What is phase angle between fixed and moving coil in single phase electro dynamo
meter type PF meter.
6. What is phase angle between fixed and moving coil in three phase electro dynamo
meter type PF meter.
7. How many types of power factors you know?
Exp. No. :
Date :
3. Crompton D. C Potentiometer
Calibration of PMMC Ammeter and PMMC Voltmeter
AIM: To calibrate the given 0-5A moving coil ammeter and 0-230V moving voltmeter
APPARATUS REQUIRED:
Crompton DC Potentiometer,
Moving coil Ammeter
Regulated Power Supply
Galvo Meter
Standard Resistance
Voltage Ratio Box
CIRCUIT
DIAGRAM:
Procedure for standardization:
Connect circuit as shown in figure.
Vary the potentiometer main dial for large variation and coursed fine variation till
galvometer deflection is zero. The potentiometer is said to standardized.
Calibration of Voltmeter:
CIRCUIT DIAGRAM
PROCEDURE:
Connect known value of voltmeter to potentiometer circuit through voltage ratio box.
Apply voltage to the voltmeter (under calibration) by varying rheostat fine and coarse till
galvo meter reading is zero and calculate voltage drop across slide wire of potentiometer.
Calculate error by comparing measured value with true value and note down in the
tabular column.
TABULAR COLUMN:
Sl. No. Measured Value True Value Error % Error
1.
RESULT:
CALIBRATION OF VOLTMETER
CIRCUIT DIAGRAM:
PROCEDURE:
Connect the circuit as shown in figure, a standard resistance of suitable value and
sufficient current carrying capacity is placed in series with ammeter under calibration.
The voltage across standard resistance is measured with the help of potentiometer.
Calculate current through standard resistance S
Vsi
Vs – Voltage across standard resistance
S – Resistance of standard resistor
TABULAR COULMN:
Sl. No. Measured Value True Value Error % Error
1.
RESULT:
VIVA QUESTIONS:
1. What is standardization of potentiometer?
2. How many DC potentiometers you know?
3. How many AC potentiometers you know?
4. Can you use a AC potentiometer for calibrating DC quantity?
5. What are the applications of potentiometers?
6. What is difference between measurement and calibration of the instrument?
7. What is standard voltage rating of Western Standard Cell?
8. What are different parts in AC potentiometer?
9. What is the purpose of phase shifting transformer in AC potentiometer?
10. Potentiometer is which type of instrument?
Exp. No. :
Date :
4. Kelvin’s Double Bridge – Measurement of Resistance & Determination of Tolerance.
AIM: To measure the low resistance (shunt resistance of ammeter by Kelvin Double Bridge.
APPARATUS REQUIRED:
Kelvin double Bridge
Ammeter 0 – 5 A MC
Ballistic Golva meter
CIRCUIT DIAGRAM:
PROCEDURE:
Connect the circuit as shown in figure.
Range switch ‘1’ is kept in x 10 position and knob ‘2’ in 0.005 position and knob ‘3’ in
zero position.
By varying the resistance R1, the current is adjusted to 0.6A.
Balance point is obtained on the galvanometer by proper adjustment of the range switch
‘1’ and knobs 2 and 3.
The reading of the range switch and knobs for balance point is to be noted.
The experiment is to be repeated for different values of current from 0.6A to 1.8A and R
is calculated from observation.
TABULAR COLUMN:
S. No. Current
Ratio of
range
switch (M)
Reading on
dail 2
(R) Ω
Reading on
dail 3
(R) Ω
X =
M(R+r) Ω
RESULT:
VIVA QUESTIONS:
1. What are the types of resistances?
2. Which type bridge is used for measurement of low resistance?
3. What are the methods used for measurement of high resistance.
4. Which type of instrument is used for measurement of insulation resistance?
5. What are the difficulties when you are measuring low resistance?
6. What are the methods for measuring high resistance?
Exp. No. :
Date :
5. DIELECTRIC OIL TESTING USING H.T.TESTING KIT
Aim:
To determine break over voltage of given dielectric oil, using H.T testing kit.
Apparatus: 1. Dielectric oil testing kit – 1No.
2. Dielectric oil.
3.Metal strip 4MM-2.5MM – 1No
Circuit diagram
Theory:
The dielectric strength of an oil is the potential at which it starts behaving as a conducting
medium. In the HT testing kit, the oil to be tested is placed in an acrylic box consisting of two
metal electrodes. By varying the distance between electrodes and by applying high voltage across
the electrodes, the break over voltage of the oil is determined.
Dielectric strength of oil = (kV/cm)
Dielectric strength of oil decreases with moisture.
Procedure:
distance
geover voltabreak
1. Take the oil cup and adjust the gap between the electrodes with the help of gauge.
2. Fill up oil test cup with oil to be tested, close it with the lid and place it on the HT horns
under the hinged acrylic cover and close the acrylic cover properly.
3. Keep the variac in minimum position.
4. Connect the mains lead to the 220V, single phase AC 50Hz supply.
5. Switch ON the power supply by operating the toggle switch, then yellow neon bulb glows
indicating that the HT kit is switched off.
6. Press the HT ‘ON push’ switch. The red Neon lamp will start glowing and the HT
transformer circuit will be energized, the green neon bulb start glowing.
7. In case the red indication does not glow, check up the hinged acrylic cover is properly closed
and the variac knob is fully rotated in the anticlockwise direction for ‘0’ start.
8. Now start rotating the variac knob slowly in the clockwise direction till the flash over occurs
across electrodes in the oil test cup. The speed of ratio should be such that the voltage rises at
the rate of 2 kv/sec.
9. As soon as flash over occurs, the supply of the high voltage transformers, will be cut off and
the voltage pointer will also stop indications the flash over level.
Note down the reading of voltmeter and distance between the electrodes.
10. To repeat test on the sample, switch OFF the mains supply and stir the test pot with the help
of a clean rod and let it cool for sometime and close the acrylic cover properly.
11. Repeat the steps 2 to 10.
12. Switch OFF the mains supply after the tests are over.
Precautions:
1.The lid of the HT testing kit should be closed properly.
2. The variac should be kept in minimum position initially.
3. Oil cup must be kept on the HT testing horns properly.
Observations:
S.NO Distance between the
electrodes (Cm)
Break over voltage
of oil (KV)
Dielectric strength of
oil =
(kV/cm)
1
Result :
Exp. No. :
Date :
6. SCHERING BRIDGE & ANDERSON BRIDGE
AIM: To measure unknown inductance by comparing with Standard resistance and capacitance.
APPRATURS REQUIRED:
Anderson Bridge Kit
Head Phones
distance
voltageover break
CRICUIT DIAGRAM:
PROCEDURE:
DC balance
1. Make the connections as per the circuit diagram shown in figure.
2. Connect DC supply Galvanometer one unknown inductance
3. Now adjust resistance dial R and press the galvanometer key and get the balance point
in galvanometer
4. Use the resistance dial S only for fine balance to the galvanometer.
5. Note down the value of R
AC balance
1. Replace the DC supply with AC supply frequency 1KhZ. and galvanometer with head
phone.
2. Set the Standard Capacitance C at the position 0.1F and adjust the resistance dial r to
minimize the sound in the head phone.
3. Note the value of resistance dial r and calculate the value of unknown inductance using
the formula
L = CR (Q + 2r)
4. Repeat the experiment with unknown inductance and capacitance C.
TABULAR COLUMN:
Sl.
No. Capacitance C Resistance R Resistance Q Resistance r
L =
CR (Q+2r)
1.
RESULT :
SCHERING BRIDGE
AIM: To measure unknown value of capacitance by comparing with Standard Capacitance &
Resistance
APPRATURS REQUIRED:
Schering Bridge Kit
Head Phones
CRICUIT DIAGRAM:
PROCEDURE:
1. Make the connections as shown in figure 1 using AC supply of frequency 1KhZ and
head phone.
2. Connect an unknown capacitance, set the capacitance dial C2 at zero position and R
also at zero position.
3. Now introduce some resistance from decay resistance R1 to minimize the sound in
head phone.
4. With alternate adjustment of decay resistance R1 and R2 we can get the minimum
sound or no sound in the head phone.
5. Note down the values of R1 and R2 and C1. Calculate the value of unknown
capacitance by using formula.
6. Repeat the experiment with different values of unknown capacitance.
Procedure to find dissipation factor:
1. Without disturbing the setting of bridge (null point with R1 and R2) Introduce some
resistance say 500Ω from resistance dial R. There will be again some sound in the
head phone.
2. Now adjust the capacitance dial C2 to minimize the sound in the head phone.
3. Calculate the dissipation factor using formula
D = CR
Where
C is capacitance of capacitor
F is frequency of AC supply (1 KhZ)
R is series resistance of capacitor representing the loss in capacitor.
4. Repeat the experiment with different values of Resistors R.
CALCULATIONS:
3
42
R
RCCx
There Cx = Unknown Capacitor.
C2 = Standard Capacitor of 0.1, µF.
C4 = Variable Capacitor of 0.001 to 0.001, µF.
R3 = 1. KΩ (Fixed).
R4 = 1, KΩ variable resistance used for balance.
RESULT:
VIVA QUESTIONS:
1. What are the types of bridges used for measurement of inductance?
2. What are the types of bridges used for measurement of capacitance?
3. Which bridge is used for measurement of frequency?
4. What is dissipation factor?
5. Which bridge is used for measurement of di-electric strength of insulated oils?
6. Which bridge is used for measurement of premitivitve?
7. Which is bridge is used for low Q coils?
8. Which is bridge is used for measurement of High Q coils?
9. Which is bridge is used for measurement of medium Q coils?
10. What are the different types of dictators used for bridge balance?
Exp. No. :
Date :
7. MEASUREMENT OF 3-PHASE REATIVE POWER
USING SINGLE WATTMETER
AIM : To measure 3-phase reactive power using single phase wattmeter.
APPARATUS:
i. Single Phase Wattmeter – 1No.
ii. Three Phase Inductive Load
CIRCUIT DIAGRAM:
PROCEDURE:
1. Connect the circuit as shown in fig.
2. Switch ‘ON’ the supply.
3. Note down the corresponding there reading and calculate 3- reactive power.
4. Now increase the load of three phase Inductive load steps and note down the
corresponding meter readings.
5. Remove the load and switch ‘off’ the supply.
CALCULATIONS:
Voltage across pressure coil = VYB
The phase angle between VYB and IR from the phasor diagram is 90°-
Wattmeter reading is VYB IR Cos (90°-)
W = VYB IR Sin (90°-)
In terms of line current and voltage
W = VYB IR Cos (90°-)
Items of line current and voltage
W = VL IL Sin
The total 3- reactive power is √3 VL IL Sin
TABULAR COLUMN:
3 Phase Load Wattmeter Reading 3 Phase Reactive Power
1A
2A
3A
4A
5A
RESULT:
VIVA QUESTIONS:
1. What is reactive power?
2. Draw the power triangle and calculate reactive power from that?
3. How many types of methods are there for measurement of reactive power?
Exp. No. :
Date :
8. MEASUREMENT OF CHOKE COIL PARAMETER
USING 3 AMMETERS AND 3 VOLTMETERS METHOD
AIM: To measure the inductance and power factor of the choke coil using 3 Ammeter and 3
Voltmeter methods.
APPARATUS:
1. Ammeter 0-5A, – 3 No’s
2. Voltmeters 0-300V – 3 No’s
3. Resistor
4. Choke coil
5. Auto transformer
CIRCUIT DIAGRAM:
3 AMMETER METHOD
3 VOLTMETER METHOD
PROCEDURE:
3-Ammeter methods:
1. Make connections as per circuit diagram.
2. Keep the auto transformer at zero position.
3. Increase the voltage gradually and note down the current I1, I2, I3 at different steps.
3-Voltmeter method:
1. Make connections as per the circuit diagram.
2. Keep the auto transformer at zero position.
3. Switch on the power supply.
4. Increase the voltage gradually and note down the Input Voltage )V1), Voltage across R
(V2) and Voltage across choke (V3)
CALCULATIONS:
3 – Ammeter method:
From the pharos diagram
I² = I R² + I L² + 2 I L I R Cos Φ L
Cos Φ L = I² – I R² – I L² / 2 I L I R
Power drawn the load = VI L Cos Φ L
= I R R I L Cos Φ L
Since power = I R I L R (I² – I R² – I L² / 2 I L I R)
= (I² – I R² – I L²) R/2.
From the power calculated the inductance of the choke can be calculated.
3. Voltmeter method:
From the pharos diagram
V = V R + V L + 2 V R V L Cos Φ L
= V – V R V L / 2 V R V L
Power drawn by load = V L I Cos Φ L
TABULAR COLUMN
3-Ammeter Method
Voltage I IL IR COSΦ PL
3-Voltmeter Method
Voltage I IL IR COSΦ PL
RESULT:
VIVA QUESTIONS:
1. What are the parameters of choke coil.
2. How many methods are used for measurement of choke coil parameters?
Exp. No. :
Date :
9. MEASUREMENT OF 3-Φ POWER WITH SINGLE WATTMETER AND 2 NO’S OF
CT’S
Aim:
To measure the Active Power in a 3-Φ Balanced Delta connected load by using a 1-Φ UPF
Wattmeter.
Apparatus:
S. No.
Name of the Equipment
Rating
Type
Qty
1. 1-Φ Wattmeter (0-10) A, (0-600) V UPF 1 no
2. Current Transformer (0-20) A/5A 2 no’s
3. Voltmeter (0-600) V MI 1 no
4. Ammeter (0-10) A MI 1 no
5. 3-Φ Balanced R-L Load 45 Ω, 150 mH 1 no
6. 3-Φ Variac 400 V/(0-440) V, 15 A 3 no’s
Circuit Diagram:
3-Ph, 400V
AC Supply
400V/(0-440)V, 15A, 3-Ph Variac
R
B
10 A
10 A
A
Y
10 A
(0 -10)A MI
TPST SWITCH
(0 - 600)V, 10A, 1-Ph,
UPF Wattmeter
S1
S2
P1
P2
S1 S
2
P1
CT - 1,
20A / 5A
CT - 2,
20A / 5A
V
(0 -
60
0)V
M
I
R
B Y
M
L
Co
m6
00
V 45 Ohms
45 Ohms
45 Ohms150 mH
150 mH
150 mH
N
P2
N
3-Ph Balanced Load
R
Y
B
Procedure:
1. Connect the circuit as shown in the circuit diagram.
2. The TPST mains switch is closed.
3. At No-Load note down the voltage VL, current IL and Wattmeter reading as Active Power
(Pa) in Watts.
4. Vary the Load Resistance simultaneously on each phase in equal steps. (Note:
The 3-Φ Load must be always balanced)
5. Take readings of Ammeter and Wattmeter.
6. Calculate the 3-Φ Active Power Pa=W*M.F of Wattmeter*C T Ratio
Where W is Wattmeter reading
Tabular Columns:
Rated Voltage VL= _ _ _ _
S. No
IL (A)
Wattmeter
Reading
3-Φ Active Power (Pa)
Theoretical
Practical
Theory:
This method is applicable only when the 3-Ф load is perfectly balanced. It is seen from
the Phasor Diagram that, for the balanced load, the three line currents also form a 3-Ф system,
with 1200 apart and equal magnitude.
Hence the angle between VRY and IRY is
same as that between VR and IR. Also
VRY = VRN
− VYN
IRY = IR − IY
This method is practically very useful because
all 3-Ф machines are balanced and 1-Ф loads if any,
or equally distributed on the three phases.
VR
VRY
IRY
IR
IB
IY
VY
VB
300
300
0
0
Result:
Exp. No. :
Date :
10. RESISTANCE STRAIN GUAGE-
STRAIN MEASUREMENT AND CALIBRATION
AIM: To measure mechanical quantities like strain, by conducting experiment.
APPRATUS REQUIRED:
Strain Gauge trainer Kit
Weights (100 grms to 1 Kg.)
CIRCUIT DIAGRAM:
PROCEDURE:
Check connections made and switch on the instrument by toggle switch at the back of the
box. The display glows to indicate the instrument is ON.
Allow the instrument in ON position for 10 minutes for initial warm up.
Select full or half bridge configuration from the selector switch on the panel.
Adjust the zero potentiometer on the panel till the display reads ‘000’.
Apply 1 Kg. load on the canti lever beam and adjust the CAL potentiometer till the
displays reads 377 micro strain.
Remove the weights the display should come to ‘000’ increasing of any variation. Adjust
the zero pot again and repeat the procedure again. Now the instrumented is calibrated to
read microstrain.
Apply load on sensor using loading arrangement provided in steps of 100 grms, upto 1 Kg.
The instrument displays exact micro strained by Canti lever beam (for full bridge and half
bridge configurations.
Note down the readings in tabular column. Percentage error in readings hysteresis and
Accuracy of the instrument can be calculated by comparing with the theoretical values.
CALCULATIONS:
S = EBT
PL2
)6(
P = load applied in Kgs.
L = effective length of the beam in cm (22 cm)
B = Width of the beam (2.8 cm)
T = Thickness of the beam (0.25 cm)
E = Youngs modulus (2 X 106)
S = Microstrain
MODEL GRAPHS:
TABULAR COLUMN:
Sl. No. Weight
(in grams)
Actual Reading
(S)
Indicator
Reading
(D)
ERROR
in %
% Error = gramsinWeightsMax
DadingIndicatorSadingAcutal
.
)(Re)(Re( X 100
RESULT:
VIVA QUESTIONS:
1. What is strain Gauge?
2. Define Gauge Factor?
3. How many types of bridges you know for measurement of Strain?
4. Define Half Bridge?
5. Define Quarter Bridge?
6. What is the difference between Full Bridge & Half Bridge?
7. What is the difference between Half Bridge & Quarter Bridge?
8. Write expression for sensitivity of Full Bridge?
9. Write expression for sensitivity of Half Bridge?
10. Write expression for sensitivity of Quarter Bridge?
11. MEASUREMENT OF 3-PHASE REATIVE POWER
USING TWO WATTMETERS
AIM : To measure 3-phase power using two wattmeters.
APPARATUS:
iii. Single Phase Wattmeter – 2 Nos.
iv. Three Phase Resistive Load
CIRCUIT DIAGRAM:
PROCEDURE:
1. Connect the circuit as shown in fig.
2. Switch ‘ON’ the supply.
3. Note down the corresponding there reading and calculate 3- reactive power.
4. Now increase the load of three phase Inductive load steps and note down the
corresponding meter readings.
5. Remove the load and switch ‘off’ the supply.
CALCULATIONS:
Reading of P1 wattmeter, P = VI cos (30- Ǿ) = √3 VI cos (30- Ǿ)
The current through wattmeter P2 is I and voltages across its pressure coil is V I lags V by an an
angle (30 + Ǿ)
Reading of P2 wattmeter, P = VI cos (30 + Ǿ) = √3 VI cos (30 + Ǿ)
Sum of reading of two Wattmeters
P1 + P2 = √3 VI [ cos (30 - Ǿ) - cos (30 + Ǿ)]
3VI cos Ǿ this is total power consumed by load P = P1 + P2
Difference of readings of two Wattmeters
P1 – P2 = √3 VI [ cos (30- Ǿ) - cos (30 + Ǿ)]
= √3 VI sin Ǿ
21
21
PP
PP
=
CosVI
SinVI
3
3 =
3
tan or θ = tan -3
21
21
PP
PP
Power factor Cos Ǿ = Cos tan -3 21
21
PP
PP
Current through the current coil = I
Voltage across the pressure coil = V
Q = 3 VI sin Ǿ = - √3 * reading of wattmeter
Phase angle Ǿ tan P
Q
TABULAR COLUMN:
Load Current Wattmeter Reading 3 Phase Reactive Power
VIVA QUESTIONS:
1. Can you measure reactive power using two wattmeter method.
2. Can you use two wattmeter method for both balanced and unbalance loads.
3. What is the expression for power factor in two wattmeter method?
4. What are the main sources of error in watt meter?
5. In Two Watt Meter Method one watt meter shows positive and another watt meter shows
negative reading. What will be the power factor range?
6. In Two Watt Meter Method one watt meter shows zero reading, what will be the power
factor?
7. What are the causes of errors in watt meters?
8. How can you eliminate inductance effect in a watt meter?
9. What is difference between UPF and LPF wattmeter?
Exp. No. :
Date :
CALIBRATION OF LPF WATTMETER BY PHANTOM LOADING
AIM:
To calibration of LPF wattmeter by phantom loading.
APPARATUS:
S.No Equipment Range Type Quantity
1 Ammeter 0-10A AC
2 Voltmeters 300V AC
3 Rheostat AC
4 single phase variac 10A AC
5 LPF wattmeter AC
6 Power factor meter
CIRCUIT DIAGRAM:
THEORY:
When the current rating of a meter under test is high a test with actual loading arrangements
would involve a considerable waste of power. In order to avoid this “Phantom” or Fictitious”
loading is done.
Phantom loading consists of supplying the pressure circuit from a circuit of required normal
voltage, and the current from a separate low voltage supply as the impedance of this circuit very
low. With this arrangement the total power supplied for the test is that due to the small pressure
coil current at normal voltage, plus that due to the current circuit current supplied at low voltage.
The total power, therefore, required for testing the meter with phantom loading is comparatively
very small.
Wattmeter reading = Actual reading
Theoretical reading P = V I cosΦ
P = Voltmeter reading X Ammeter reading X power factor reading
Actual reading - Theoretical reading
Since percentage of error = -------------------- ------------------------ X 100
Theoretical reading
PROCEDURE:
1. Keep the Auto transformer at zero position.
2. Make connections as per the Circuit diagram shown below.
3. Switch on the 230 VAC, 50 Hz. power supplies.
4. Increase the input voltage gradually by rotating the Auto transformer in clockwise direction.
5. Adjust the load rheostat so that sufficient current flows in the circuit. Please note that the
current should be less than 4A.
6. Note down the Voltmeter, Ammeter, Wattmeter and power factor meter readings for different
voltages as per the tabular column.
7. Find out the percentage error by using above equations.
TABULAR COLUMN:
S. No. I in AMPS V in volts Wattmeter Reading Power factor % Error
RESULT:
VIVA QUESTIONS:
Viva Voce Questions
1. What is the difference between moving coil & Fixed coil.
2. What type of control is used for electrodynamometer? Type wattmeter.
3. What is damping.
4. What type of scales & pointers used for electro Dynamometer wattmeter?
5. What are the different types of errors occur as the Wattmeter.
6. What is the power factor?
7. Explain the shape scale.
8. How the current is related with the voltage in current coil?
9. On What principle does the power factor meter work?
10. How the torque is developed in case of power factor meter?
Exp. No. :
Date :
12. LINEAR VARIABLE DISPLACEMENT TRANSDUCER
AIM: To measure output voltage due to small change in displacement.
APPRATUS REQUIRED:
LVDT Trainer Kit.
CIRCUIT DIAGRAM:
PROC
EDUR
E:
Connect the power supply cord 230V/50hZ. Switch on the instrument by pressing down
the toggle switch. The display glows to indicate the instrument is ON.
Allow the instrument in ON position for 10 minutes for initial warm up. Rotate the micro
meter till it reads “20”.
Adjust the CAL potentiometer at the front panel so that the display reads “10”.
Rotate the core of micro meter, till it reads “10”. And adjust the zero potentiometer till the
display shows “00”.
Rotate back the micro meter core upto “20” and adjust once again CAL potentiometer till
the display shows 10.0.
Now the instrument is calibrated for 10.0 mm range. As the core of LVDT moves
displays reads the displacement in mm.
Rotate the core of the micro meter in steps of one or two mm and tabulate the readings.
The micro meter will show the extract displacement given to the LVDT core. The display
will read the displacement sensed by LVDT. Tabulate the readings and plot the graph
between actual reading vs Indicated reading.
MODEL GRAPHS:
TABULAR COLUMN:
Sl. No.
(B)
ACTUAL
MICROMETER
READING
(mm)
(C)
INDICATOR
READINGS
LVDT
(mm)
(D)
Error = (B – C)
(E)
% Error
1. 0
2. 2
3. 4
4. 6
5. 8
6. 10
7. 12
8. 14
9. 16
10. 18
11. 20
RESULT:
VIVA QUESTIONS:
1. What is LVDT?
2. LVDT is which type of transducer?
3. Draw the output characteristics of LVDT?
4. What is sensitivity of LVDT?
5. What are the applications of LVDT?
6. What is RVDT?
7. What is the difference between LVDT and RVDT?
8. The Principle of LVDT is similar to ______________________.
Exp. No. :
Date :
13. MEASUREMENT OF PERCENTAGE RATIO ERROR & PHASE ANGLE OF
GIVEN CT BY COMPARISION (SILSBEE’S) METHOD
Aim: To test the given Current Transformer by Silsbee’s Method.
Apparatus:
S. No.
Name of the Apparatus Range Type Qty
1. Voltmeter (0-300)V MI 1 no
2. Ammeter (0-30) A
(0-5) A
MI
MI
1 no
1 no
3. Test Transformer 30A/ 5A, Class 2.0 1 no
4. Standard Transformer
(Multitap Primary & 5A Secondary)
Class 0.5 1 no
5. 3-Ф Phase Shifting Transformer 1 no
6. CT Burden 1 no
7. 1-Ф Dynamometer Wattmeter (0-150V)/ 300V, 5A
(0-150)V/ 300V, 1A, 0.2pf
UPF
LPF
1 no
1 no
Circuit Diagram:
R
B
Y
5 A
V (0 - 300)V
MI
C1
B1
5 A
5 A
A1
A2
B2
C2
300V
C
a1
a2
b1
c1
b2
c2
A
(0-5
)A M
I
A
(0-30)A
MI
Sta
nd
ard
Bu
rden
5 A
5 A
N
Ph
Com 30 A
M L
P1
P2
S2S
1
ISS
ISX
I
300VM
CL
M
230V
AC Supply
3-Ph, 400V
AC Supply
L
Booster Transformer
230V/(0-40)V, 30A(0
-15
0)V
/30
0V
,
1A
, 0.2
pf,
LP
F
(0-150)V/300V,
5A, UPF
Standard Transformer
Class 0.5
Test Transformer
Class 2.0
Switch
TPST Switch
Circuit Diagram (a)
N
3-Ph Phase
Shifting Transformer
IP
Theory:
This is a Comparision method and the errors of the Test Transformer are obtained in
terms of the errors of the Standard Transformer and Wattmeter readings.
The Standard Current Transformer has got a ratio error of +0.5% and phase angle error of
5 minutes. The nominal ratio of the Standard Current Transformer is made equal to nominal ratio
of the Test Current Transformer by using the proper tap on the Primary (In this case 30A/5A).
Phasor Diagrams:
IP
ISS
ISX
(0X-0
X)
0X
0S
ISS
ISX
(0X-0
X)
IQ
I
IIN
In the Phasor Diagram it is seen that ISX is secondary current of the Test Current Transformer and
ISS is secondary current of the Standard Current Transformer.
The error current = ∆I = ISS - ISX
The In-phase component of ∆I, ∆IIN is In-phase with ISS & ∆IQ is Quadrature with ISS. Two
readings are taken by first aligning the Pressure Coil voltage of Wattmeter ‘V’ along with ISS
(In-phase reading) and aligning V in Quadrature with ISS (Quadrature reading). In this case W1
will read zero.
The Primary current is common for both the Current Transformers.
In-phase:
W1-IN = V * ISS and W2-IN = V * ∆IIN
Quadrature:
W1-Q = 0 and W2-Q = V * ∆IQ = V * ISX * Sin(ӨX - ӨS)
∆ IIN = ISS - ISX * Cos(ӨX - ӨS)
∆IQ = ISX * Sin(ӨX - ӨS)
W2-IN = V * ∆IIN
= V * ISS - ISX * Cos(ӨX - ӨS)
= W1-IN - V * ISX * Cos(ӨX - ӨS)
V * ISX * Cos(ӨX - ӨS) = W1-IN - W2-IN ------------ (i)
V * ISX * Sin(ӨX - ӨS) = W2-Q ------------- (ii)
Ratio of Equ-(i) & (ii) gives
tan(θX−θS) = W2−Q
(W1−IN − W2−IN) ≈ (θX−θS),
(θX−θS) is very small
Therefore Phase Angle θX (rad)
= θS + W2−Q
(W1−IN− W2−IN) . . . . . . . . . . . . . . (iii)
Where θS = 5 minutes = 5
60∗
π
180 rad
∴ θX = θX(rad) ∗ 180
π∗ 60 minutes
V * ISS = W1-IN . . . . . . . . . . . . . . (iv)
V * ISX = W1-IN - W2-IN . . . . . . . . . . . . . . (v)
Ratio of Equ-(iv) & (v) gives
(ISS|IP)
(ISX|IP) =
W1−IN
(W1−IN
− W2−IN) =
(R.T)X
(R.T)S
% Ratio Error
For the Standard Current Transformer Ratio Error = RN − RT
RT
i.e, ± 0.005 = (
30
5 − RT)
RT
∴ RT = RTS = 6
1.005= 5.97
RTX = W1−IN
(W1−IN
− W2−IN) ∗ RTS
% Ratio Error = (
30
6 − RTX)
RTX ∗ 100
(Since the Nominal ratio of Test Ct isRN = 30
6 )
Procedure:
1) Note down the nominal ratio of the Test Current Transformer and set the same ratio on
the Standard Current Transformer.
2) Two primary windings of two Current Transformers are connected in series and the rated
primary current is passed through with the help of the Booster Transformer.
3) Switch ON the 3-Ф AC supply to the Phase-Shifting Transformer and adjust the
voltmeter reading to 150V and set the normal value of the Burden in the Current
Transformer secondary circuit.
4) Adjust the Rotor handle of the Phase-Shifting Transformer till UPF Wattmeter ‘W1’ reads
maximum.
5) Note down the readings of W1-IN & W2-IN.
6) Adjust the Rotor handle of the Phase-Shifting Transformer to make the shift by 900 in the
positive direction.
7) This is Quadrature reading, so W1-IN = 0.
8) Note down the reading of W2-Q.
9) Compute the percentage ratio error and phase angle of the Test Current Transformer as
explained in the Theory above.
10) Vary the burden to different values such as 25%, 50%, 75%, 100% and 125% of the rated
value.
11) Repeat the above procedure.
Graph:
Plot a graph with % Ratio Error and Phase Angle of the Test Current Transformer vs %
Burden.
Expected Graph:
Burden0 25 50 75 100 125
% Ratio
Error
0
Phase
Error
Burden025 50 75 100 125
% Ratio Error is within ± 3%
Tabular Columns:
Voltage=
S.
No.
IP
ISC
W1
(UPF)
W2
(LPF)
% Burden
% Ratio
Error
% Angle
Error
In-
phase
Qua
In-
phase
Qua
In-
phase
Qua
In-
phase
Qua
In-
phase
Qua
In-
phase
Qua
Calculations:
Conclusions:
VIVA QUESTIONS:
1. How many types of tests are available for testing of instrument transformer?
2. How many types of tests are available for testing of current transformer?
3. How many types of tests are available for testing of potential transformer?
4. Which type of instrument is called Step Up Transformer?
5. Which type of instrument is called Step Down Transformer?
6. Why secondary of current transformer ever be open circuited.
7. What is nominal ratio of a current transformer?
8. What is phase angle error?
9. What is ratio error?
10. What is necessity of calculating phase angle and ratio errors?
11. What are applications of CTs and PTs in Electrical Engineering?
Exp. No. :
Date :
12. EARTH TESTER
AIM:
To Measure The Earth Resistance.
APPARATUS:
1. Earth Tester-1 no.
2. Spikes --2 No.s
CIRCUIT DIAGRAM:
PROCEDURE:-
1) Put the two spikes acting as current & potential electrode in to the ground at a distance of
25 m & 12.5 m from earth electrode under test.
2) Connect the two spikes to E2 & P2 terminals respectively.
3) Short the P1 & E1 terminals of motor & connect it to the earth electrode under test. 4)
Place the earth tester on horizontal firm stud.
5) Turn the handle of earth tester to speed slightly higher than rated speed & note down the
deflection of the needle.
6) Take down the 3 to 4 readings by keeping the distance same and placing the electrodes at
the other positions.
7) Take the average of these readings which is equal to earth resistance.
RESULT:-
The value of earth resistance by direct method is ------------- Ω.