47512039 m-i-lab-manual

Gnanamani College of
Engineering
NH-7, pachal, Namakkal – 6301018
MEASUREMENTS AND
INSTRUMENTATION LABORATORY
MANUAL
NAME: __________________________________________________
YEAR/SEM: ________________________________ROLL NO______
DEPT.:__________________________________________________

TABLE OF CONTENTS
Ex.
No.
Date Title of the Experiment
Page
No.
Marks
awarded
Remarks
Total Marks
Average Marks
Lab Completed Date
Staff Signature :

MEASUREMENTS AND
INSTRUMENTATION LABORATORY
Manual
Third Semester B.E.
( EEE )
Anna University - Coimbatore
By
Gandhi.R ,ME
Department of EEE
Gnanamani College of Engineering
NH -7, pachal
Namakkal – 637018

PREFACE
This manual“MEASURMENT &INSTRUMENT” has been
written primarily for Practical for Third semester EEE for the
academic year 2010-2011.
This manual covers all the experiments prescribed by
Anna University – Coimbatore and the experiments are
explained with supportive diagrams and tables.Students can
enter the readings and perform all the calculations in the work
sheets and graph sheets provided in the manual.
We take this opportunity to thank the Management of
Gnanamani College of Engineering and Dr.D.TENSING, Principal,
Gnanamani College of Engineering for the continuous support
and encouragement in completing this work.

Gananamani College of
Engineering
NH-7,Pachal,Namakkal-63019
LIST OF EXPERIMENTS
SL.N
O
NAME OF THE EXPERIMENTS PAGE.N
O
1 STUDY OF DISPLACEMENT TRANSDUCER.
2 PRESSURE TRANSDUCER.
3 AC BRIDGE- SCHERING’S BRIDGE .
4 AC BRIDGE- MAXWELL’S INDUCTANCE,
CAPACITANCE BRIDGE.
5 DC BRIDGES -WHEATSTONE BRIDGE
6 DC BRIDGES -KELVINS DOUBLE BRIDGE
7 INSTRUMENTATION AMPLIFIER
8 A/D CONVERTER AND D/A CONVERTER
9 STUDY OF TRANSIENTS
10 CALIBRATION OF SINGLE-PHASE ENERGY METER
11 MEASUREMENT OF THREE-PHASE POWER AND
POWER FACTOR
12 CALIBRATION OF CURRENT TRANSFORMER
13 MEASUREMENT OF IRON LOSS

CIRCUIT DIAGRAM
LINEAR VARIABLE DIFFERENRIAL TRANSFORMER

Exp.No:
Date:
STUDY OF DISPLACEMENT TRANSDUCER
(Linear Variable differential Transformer)
AIM
To obtain the performance characteristics of Linear Variable
differential Transformer (LVDT).
Find the residual voltage and non-electrical quantity displacement in
terms of voltage.
REFERENCE
1. A.K. Sawhney : A course in Electrical and Electronics Measurements
and Instrumentation, Dhanpat Rai & Sons, 1984.
2. H.S. Kalsi : Electronic Instrumentation, TMH, 1995.
BASIC KNOWLEDGE REQUIRED
Principle of working of Linear Variable Differential Transformer and
different transducers.
APPARATUS REQUIRED
SL.NO APPARATUS RANGE QUANTITY
1 LVDT Trainer kit - 1
2 LVDT setup - 1
3 Multimeter (CRO) Electronic 1
4 Power Chord - 1
THEORY
Linear Variable Differential Transformer (LVDT)
The linear variable differential transformer (LVDT) is a type of
electrical transformer used for measuring linear displacement. The
transformer has three solenoid coils placed end-to-end around a tube. The
centre coil is the primary, and the two outer coils are the secondary. A
cylindrical ferromagnetic core, attached to the object whose position is to
be measured, slides along the axis of the tube.
An alternating current is driven through the primary, causing a
voltage to be induced in each secondary proportional to its mutual
inductance with the primary. The frequency is usually in the range of 1 to
10 kHz.

As the core moves, these mutual inductances change, causing the
voltages induced in the secondary to change. The coils are connected in
reverse series, so that the output voltage is the difference (hence
"differential") between the two secondary voltages. When the core is in its
central position, equidistant between the two secondary, equal but
opposite voltages are induced in these two coils; so the output voltage is
zero.
When the core is displaced in one direction, the voltage in one coil
increases as the other decreases, causing the output voltage to increase
from zero to a maximum. This Voltage is in phase with the primary voltage.
When the core moves in the other direction, the output voltage also
increases from zero to a maximum, but its phase is opposite to that of the
primary. The magnitude of the output voltage is proportional to the
distance moved by the core (up to its limit of travel). The phase of the
voltage indicates the direction of the displacement because the sliding core
does not touch the inside of the tube, it can move without friction, making
the LVDT a highly reliable device. The absence of any sliding or rotating
contacts allows the LVDT to be completely sealed against the environment.
PROCEDURE
1. Make the Connections for the given LVDT kit.
2. Calibrate the LVDT.
3. Place the core of the LVDT to 10 mm by adjusting the micrometer.
4. Gradually increase the micrometer displacement from 10mm to
20mm and note down the forward core displacement from zero mm
to 10mm on the display and measure the secondary output voltage
(mV) across T4 and T7.
5. Similarly, decrease the micrometer displacement from 10mm to zero
mm and note down the reverse core displacement of zero to 10mm
on the display and measure the secondary output voltage (mV)
across T4 and T7.
6. Tabulate the reading of the core displacement, micrometer
displacement and secondary output voltage (mV).
7. Plot the graph between core displacement (mm) along X axis and
secondary output voltage (mV) across Y axis.

8. When the displacement of the core is zero measure the voltage. This
voltage is the residual voltage.
TABULATION
Micrometer
Displacement(m
m)
Core
Displacemen
t (mm)
Secondary
Output Voltage
(mV)
MODEL GRAPH
Displacement (mm)
O/pvoltage(mV)

DISCUSSION QUESTIONS
1. Mention some of the transducers.
Variable Resistor, Variable inductor, Variable capacitor, Synchros
& Resolvers
2. State the advantages of LVDT.
The advantages of LVDT are
(i) Linearity
(ii) Infinite resolution
(iii) High output
(iv) High sensitivity
(v) Ruggedness
(vi) Less friction
(vii) Less hysterices
(viii) Less power consumption
3. State the disadvantages of LVDT?
The disadvantages of LVDT are
(i) Large displacements are necessary for appreciable
differential output
(ii) They are sensitive to stray magnetic field
(iii) Dynamic response is limited by mass of core
(iv) Variation in temperature affects the transducer.
Performance
Record 05
Viva voce 05
Total 50
RESULT
Thus the characteristics of LVDT position sensor with respect to
the secondary output voltage is obtained.
Thus, the residual voltage and non-electrical quantity displacement in
terms of voltage are found.

CIRCUIT DIAGRAM
89
+
-
Sensor
Timer
State
+
-
+
-
Gain
Amplifi
er
PSI
Constan
t
Voltage
Source
To
excitation
Instrumentation
Amplifier
R6
R5
R3
R2
R1
R4
T2
T3
T4
C3
+
_
Zero
R7
R9
T
1
R8

Exp.No:
Date:
PRESSURE TRANSDUCER
AIM
To draw the characteristics curve for a given Bourdon tube ie Pressure
Vs output
(V or I) and measure the non electrical quantity pressure in terms of
voltage (or) current.
REFERENCE
1. A.K. Sawhney: A course in Electrical and Electronics Measurements and
Instrumentation, Dhanpat Rai & Sons, 1984.
Principle of working of pressure transducers, different types of pressure
transducers
APPARATUS REQUIRED
1 Pressure Transducer Trainer
kit
- 1
2 Multimeter (mV) Electronic 1
3 Pressure cell Setup - 1
4 Power Chord - 1
THEORY
Pressure Transducer
Most pressure measuring devices use elastic members for sensing
pressure at the primary stage. These elastic members are of many types and
convert the pressure into mechanical displacement, which is later converted
into an electrical form using secondary transducers. These devices are many a
time known as force summing devices.
The commonly used pressure sensitive devices are described below:
(i)Bourdon tubes:
Bourdon tubes are made out of an elliptically flattened tube bent in
such a way to produce the below mentioned shapes. They are
a) C type b) spiral c) twisted tube and d) helical
Bourdon tube elements have several advantages and these include low cost,
simple construction, high pressure range, good accuracy except at low
pressure, and improved designs at the pressure for maximum safety. Their
greatest advantage is that they easily adapted for designs for obtaining
electrical outputs.
89

MODEL GRAPH
89
Test
specimen
Active Gauge
Dummy GaugeR1
R2
Strain Gauge
SET UP
BLOCK DIAGRAM
Transducer Bridge
Calibration &
Zeroing
network
Measure
-ment
DC
Excitation
Source
Power
supply
DC
Network
e
Low Pass
Filter

PROCEDURE
1. Install the pressure cell setup and interface the 9 pin D connector with
Pressure transducer trainer kit.
2. Connect the Multimeter (in milli volt mode) across T2 and T3 for bridge
voltage measurement.
3. Switch “ON” the module.
4. Initially, open the air release valve and exhaust the tank inlet air and
nullify the bridge voltage by using zero adjustment POT.
5. Now, close the opened air release valve by pressing the pump position,
the pump sucks the air from atmosphere and supply to the cylinder.
Pressure will be developed in the cylinder and now measure the bridge
voltage (mV) across T2 and T3.
6. Gradually increase the pressure by pressing the pump piston and note
down the bridge voltage (mV) for corresponding gauge pressure.
7. Tabulate the readings and plot a graph between gauge Pressure and
bridge voltage (mV).
89

TABULATION
S.No.
Gauge Pressure
(psig)
Displayed pressure(psi)
MODEL CALCULATION
89

DISCUSSION QUESTION
1. Define transducer?
It is a device which converts a non electrical quantity into an
electrical
quantity
2. What is the pressure transducer?
It is a device which converts the pressure into mechanical
displacement which is later converted in to electrical quantity using a
secondary transducer.
3. Give commonly used pressure sensitive devices?
The commonly used pressure sensitive devices are bourdon tubes,
bellows and diaphragms.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the characteristics of the pressure cell with respect to bridge voltage
are plotted and the non electrical quantity pressure in terms of voltage or
current is measured.
89

AC BRIDGE- SCHERING’S BRIDGE
89
DAFO
R3
C1 C2
R4
C3
RX

Exp.No:
Date:
AC BRIDGE- SCHERING’S BRIDGE
AIM
To determine the value of the unknown capacitance and loss angle (δ)
using low voltage Schering’s bridge.
REFERENCE
1. A.K.Sawhney: A course in Electrical and Electronics Measurements and
2. H.S.Kalsi : Electronic Instrumentation, TMH, 1985.
Principle of bridge circuits, loss angle, high voltage Schering
Bridge for measurement of capacitance and low voltage Schering bridge for
measurement of capacitance.
APPARATUS REQUIRED
1 Schering bridge - 1
2 Decade capacitance
box
- 1
3 Multimeter Electronic 1
4 Patch Chord - 1
5. CRO 1
THEORY
A very important bridge used for the precision measurement of
capacitors and their insulating properties is the Schering Bridge. The standard
Capacitor C2 is a high quality mica capacitor (low-loss) for general
measurements or an air capacitor (having a very stable value and a very small
electric field) for insulation measurement.
Under balance condition,
{R1+[1/jωC1]}{R4/[1+jωC4R4]} = {I/jωC2}R3
{R1+1/jωC1}R = R3/jωC2[1+jωC4R4]
R1R4-[jR4/ωC1] = -[jR3/ωC2]+ [R3C4R4/C2]
C1=C2R4/R3
89

Equating real and imaginary terms, R1= R3C4/C2
TABULATION
89
SL.
No.
Capacit
or
C2 (µf)
R4
(KΩ)
C4
(µf)
R3
(Ω)
C1
Actual
Value
(µf)
C1
obtain
ed
Value
(µf)
%
Error
δ

FORMULAE
Two independent balance equations are balanced if C4&R4 are
chosen are the variable element.
C1= C2 ( R3 / R4) cos2
δ Farad
Where,
R3 – Variable resistance (Ohm)
R4 – Standard resistance (Ohm)
C1 – unknown Capacitance (Farad)
C2 – Standard Capacitance (Farad)
Loss angle δ = tan-1
(ω C4 R4)
C4 – Variable Capacitance (Farad)
% Error = ((Actual Value – Obtained Value) / Actual Value) * 100
Dissipation factor D1=tan δ=ωC1R1
=ω[C2R4/R3][R3C4/C2]
=ωC4 R4
This bridge is widely used for testing small capacitors at low
voltages with very high precision.
89

PROCEDURE
1. Connections are made as per the connection diagram shown in fig.
2. Connect the unknown capacitance at the C1 (unknown) point.
3. Keep R4,R3 in minimum position.
4. Connect the CRO across P and Q.
5. Switch on the unit.
6. Vary resistance R3 to some extent .(above 2K is suggested)
7. Choose C2, Such that you can obtain the maximum variation the output.
8. Vary the potentiometer R4 such that the amplitude of sine wave
decreases, reaches zero and then it will start increasing, at that point
stop the tuning and vary R3 .Here also the amplitude of the sine wave
will decrease and at one point it will obtain a minimum of zero
amplitude and then it will start increasing, at that point stop the tuning.
9. Repeat the above step such that you will obtain minimum amplitude or
zero amplitude.
10. Remove the patching at R3 andR4, find the resistance using the
multimeter and note down the reading in the table given and calculate
the value of unknown capacitance.
11. One can verify the balancing condition by connecting the bridge output
(P&Q) to the input (P&Q) of audio power amplifier and you can hear a
minimum noise or no noise .If you vary the potentiometer R4 you can
hear a maximum noise.
WORK SHEET
89

1. How can we eliminate the error?
Earthed screens are provided in order to avoid errors caused due to inter
capacitance between high and low arms of the bridge.
2. Applications of Schering’s bridge?
Used in measurement of capacitance, measurement of insulators,
insulating coils.
3. What is the use of vibration galvanometer?
They are used for power and low audio frequency range.
4. List out commonly used detectors for Ac Bridge.
1. Head phones
2. Vibration galvanometer
`
Performance 25
89

Record 15
Viva voce 10
Total 50
RESULT
Thus the value of the unknown capacitance and loss angle (δ) using
low voltage Schering’s bridge are determined.
CIRCUIT DIAGRAM
AC BRIDGE-MAXWELL’S INDUCTANCE,CAPACITANCE BRIDGE
89
E
RX
LX
R3
R1
R2
C
D
C

Exp.No:
Date:
AC BRIDGE-MAXWELL’S INDUCATNCE,CAPACITANCE BRIDGE
AIM
To measure the unknown value of the inductance using Maxwell’s
Inductance Bridge and also to find the Q factor of the coil.
REFERENCE
1. A.K.Sawhney: A course in Electrical and Electronics
Measurements and Instrumentation, Dhanpat Rai & Sons,1984.
2. H.S.Kalsi :Electronic Instrumentation,TMH,1995
89

Principle of bridge circuits, low frequency and high frequency inductance
measurements.
APPARATUS REQUIRED
1 Maxwells Trainer kit - 1
2 Unknown
inductance
- 1
4 CRO - 1
5 Patch chord - 1
THEORY
Maxwell’s bridge measures an unknown inductance in terms of a
known capacitor. The use of standard arm offers the advantage of
compactness and easy shielding. The capacitor is almost a loss-less
component. One arm has a resistance R1 in parallel with C1, and hence it is
easier to write the balance equation using the admittance of arm 1 instead of
the impedance.
The general equation for bridge balance is
Z1Zx = Z2Z3
Zx = Z2Z3/ Z1 = Z2Z3Y1
Where, Z1=R1 in parallel with C1 i.e. Y1=1/Z1
Y1=1/R1 + jωC1
TABULATION
S.N
o
R2
(KΩ
)
R3
(K
Ω)
RX
(KΩ)
RX (Ω) LX (Ω)
Actual Practical Actual
Practica
l
89

MODEL CALCULATION
Z2=R2 & Z3=R3
Zx=Rx in series with Lx=Rx + jωLx
From equations we have,
Rx + jωLx = R2R3(1/R1 + jωC1)
89

Rx + jωLx = R2R3/R1 + jωC1R2R3
Equating real terms and imaginary terms we have
Rx = R2R3/R1 and Lx=C1R2R3
Also Q = ωLx/Rx = (ωC1R2R3 * R1)/R2R3 = ωC1R1
Maxwell’s bridge is limited to the measurement of low Q values (1-10).
The measurement is independent of the excitation frequency. The scale of the
resistance can be calibrated to read inductance directly.
The Maxwell’s bridge using a fixed capacitor has the disadvantage that
there is an interaction between the resistance and reactance balances. This
can be avoided by varying the capacitances, instead of R2 and R3, to obtain a
reactance balance. However, the bridge can be made to read directly in Q.
This bridge is particularly suited for inductance measurements, since
comparison with a capacitor is more ideal than with another inductance.
Commercial bridges measure from 1-1000 H, with + 2% error. (If the Q is very
large, R1 becomes excessively large and it is impractical to obtain a
satisfactory variable standard resistance in the range of values required)
PROCEDURE
1. Connections are made as per the connection diagram shown in fig.
2. Connect the unknown inductance at the Lx (unknown) point.
3. Connect the CRO across P and Q.
5. Choose R3, such that you can obtain a maximum variation of output.
6. Now set R2 to maximum position.
7. Vary the potentiometer R4 such that the amplitude of sine wave will
decrease and at one point it will obtain a minimum of zero amplitude
and then it will start increasing at that point stop the tuning and
switch OFF the line.
8. Remove the patching at R1 and find the resistance using the
multimeter and note down the reading in the table given below and
calculate the value of unknown Inductance.
9. One can verify the balancing condition by connecting the bridge
output (P&Q) to the input (P&Q) of audio power amplifier and you
can hear a minimum noise or no noise .If you vary the potentiometer
R1 you can hear a maximum noise
WORK SHEET
89

FORMULAE
RX = R2 R3 / R4(Ώ)
LX = R2 R3 C4(H)
89

Q factor=ω LX / RX
Where
LX = unknown Inductance
RX =Effective resistance of inductance LX
R2, R3, R4 = Known non – Inductance resistance
C4 = Standard capacitance
DISCUSSION QUESTION
1. What are the advantages of Maxwell’s bridge?
i) Simple to use.
ii) Useful for measurement of a wide range of inductance at power
and audio
Frequency.
2. What are the disadvantages of Maxwell’s bridge?
i) It requires a variable standard capacitor
ii) The balancing adjustments becomes difficult
3. List out A.C Bridges
i)Maxwell’s inductance bridge
ii)Hay’s bridge
iii) Schering’s bridge
iv) Anderson’s bridge
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the unknown value of inductance using Maxwell’s Inductance
Bridge was determined and the Q factor of the coil was found.
CIRCUIT DIAGRAM
89

Wheat stone’s Bridge
Exp.No:
Date:
89
D
P Q
R S
E

DC BRIDGE-Wheat stone Bridge
AIM
To determine the value of the given low resistance using Wheat
stone Bridge
REFERENCE
1. A.K.Sawhney: A course in Electrical and Electronics Measurements and
2. H.S.Kalsi : Electronic Instrumentation, TMH, 1985.
Principle and operation of bridge circuits
APPARATUS REQUIRED
1 Wheat stone Bridge Trainer
kit
- 1
2 Decade resistance box
(or) Resistance
- 1
4 Patch chord - 1
Wheat stone’s Bridge:
RX = (RSR1) / R2 (Ω)
Where,
RS – Standard resistance
r - Load resistance
RX – unknown resistance
% Error = ((Actual Value – Obtained Value) / Actual Value) * 100
TABULATION
89

Wheat stone’s Bridge
SL.No R1 (Ω) R2 (Ω) R3 (Ω)
RX (Ω)
% ErrorTheoretica
l
Practical
89

THEORY
These bridges are used not only for the measurement of
resistance but also used for measurement of various component values like
capacitor and inductor etc. Bridge circuit in its simplest form consists of a
network of four resistance arms forming a closed circuit. A source of current
detector is connected to the two junctions. The bridge circuit uses the
comparison measurement methods and operates on null-indication principle.
The bridge circuit compares the value of an unknown component with that of
an accurately known standard component. Thus the accuracy depends on the
bridge component without the null detector. Hence high degree of accuracy
can be obtained. In a bridge circuit when no current flows through the null
detector which is generally a galvanometer, then the bridge is said to be
balanced.
Wheatstone bridge
A very important device used in the measurement of medium
resistances is the Wheatstone bridge. A Wheatstone bridge has been in use
longer than almost any electrical measuring instrument. It is still an accurate
and reliable instrument for making comparison measurements and operates
upon a null indication principle. The well known expression for the balance of
Wheatstone bridge is as follows
QR = PS
If three of the resistance is known then the fourth may be determined from
the eqn,
R = S*(P/Q)
Where R is the unknown resistance, S is called the standard arm of the
bridge and P and Q are called the ratio arms.
PROCEDURE
1. Connection are made as per the circuit diagram
2. Connect the decade resistance box at Rx terminal. (Or) connect resistance
to be measured at Rx terminal
3. Now switch on the unit and vary the resistance at R1 and R3 to get the
nearest point of balance.
4. Now vary R2 to get exact point of balance.
5. Switch off the unit and remove the patching at R2.
6. Now measure the resistance at R2 by using multimeter
7. Tabulate the readings and find the value of unknown resistance.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
89

Thus the value of given resistance was determined using
Wheatstone bridge.
CIRCUIT DIAGRAM
KELVINS DOUBLE BRIDGE
89
A
D
+
+
Rb
RS
c
b
RX
R2
R4
R1
DRB
R3
DRB
a
A B
C

EX NO: DATE:
DC BRIDGE-KELVINS DOUBLE BRIDGE
AIM:
To find the value of unknown resistance using a Kelvins Double Bridge.
APPARATUS REQUIRED
1 Kelvins BridgeTrainer
kit
- 1
3 Unknown resistance - 1
4 Patch chord - 1
FORMULAE
RX = (RSR1) / R2 + R4 r (R1 / R2 – R3 / R4) / (R3 + R4 + r) (Ω)
Theory
The Kelvin Bridge is a modification of the Wheatstone bridge and
provides greatly increased accuracy in measurement of low value resistances.
An understanding of the Kelvin bridge arrangement may be obtained by a
study of the difficulties that arise in a Wheatstone bridge on account of the
resistance of the leads and the contact resistances while measuring low
valued resistors.
PROCEDURE
1. Connection are made as per the circuit diagram
2. Connect the unknown resistance at Rx terminal.
4. Select the range selection switch at the point where the meter reads least
possible value of voltage.
5. Vary the potentiometer (P1) to obtain null balance..
6. Switch off the unit and find the resistance using multimeter at P1.
89

7. Tabulate the reading and find the value of unknown resistance using above
the formula.
TABULATION:
Kelvin’s Double Bridge
SL.No R1 (Ω) R3 (Ω)
RX (Ω)
% ErrorTheoretica
l
Practical
MODEL CALCULATION
89

DISCUSSION QUESTION
1. What are the advantages of bridges?
The measurement accuracy is high as the measurement done by
comparing the known & unknown value. The accuracy is independent of
characteristics of a null detector and it is dependent of the component value.
2. What is meant by balanced condition for Wheatstone bridge?
The bridge is said to be balanced when there is no current flow through
the galvanometer so potential difference across the galvanometer should be
zero R1 R4 = R3R2
3. What is the sensitivity of Wheatstone bridge?
Sensitivity = Deflection (D)/ Sensitive current ( I)
4. What is meant by Kelvin’s bridge?
For measuring the value of resistance below 1Ω the modified form of
Wheatstone bridge is called as Kelvin’s bridge.
5. What is Kelvin double bridge?
It consists of another set of arms hence it is called as double bridge.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the value of given resistance was determined using Kelvins double
bridge.
89

CIRCUIT DIAGRAM
INSTRUMENTATION AMPLIFIER
MODEL GRAPH
Gain R1=10
89
V1
+
-
A1
R3
V2
R1
R2
R4
+
+
-
-
A3
A2
V0
o/pvoltage
I/P voltage

Exp.No:
Date:
INSTRUMENTATION AMPLIFIER
AIM
To Study the working of an Instrumentation amplifier.
REFERENCE
1. A.K. Sawhney : A course in Electrical and Electronics
Measurements and
Principle of working of Instrumentation amplifier.
APPARATUS REQUIRED
1 Instrumentation
amplifier Trainer kit
- 1
3 External millivolt
source
- 1
THEORY
In a number of industrial and consumer applications, one is
required to measure and control physical quantities. Some typical
examples are measurement and control of temperature, humidity, light
intensity, water flow etc. These physical quantities are usually
measured with the help of transducers. The output of transducers has
to be amplified so that it can drive the indicator.This function is
performed by an instrumentation amplifier.
Many of the input specification of an Op-amps employed directly
determine the input specifications of the instrumentation amplifier.
An analysis of the circuit gives the following equation:
Let R1 = R2 = R3 = R4
Considering the basic differential amplifier shown in the figure,
the output voltage V0 is given by
V0 = - R2/ R1 V2 + 1/1 + R3/R4 V1 (1+ R2/R1)
Or
V0 = R2/ R1 (V2 – 1/1 + R3/R4 (R1/ R2+1) V1V1)
V0 = -R2/R1 V2 + 1/ 1+R3/R4 V1 (1+ R2/R1)
89
V0 = -Rf / Rin (V1 –
V2)

TABULATION
Gain R1= 10
S.no
Input Voltage
(Vin)
Output Voltage
(Vo)
Gain=Vo/Vin
89

The Op-amp A1 and A2 have differential input voltage as Zero. For V1 =
V2 that is, under common mode condition, the voltage across R will be
zero. As no current flows through R and R1
the non-inverting amplifier
A1 acts as voltage follower having output V1
1 and V1. However, If V1 ≠
V2 current flows in R and R2 and (V2-V1).
The gain of an instrumentation amplifier can be varied by
changing R1 alone. High gain accuracy can be obtained by using
precision metal film resistors for all the resistances.
Because of the large negative feedback used, the amplifier has
good linearity typically about 0.01% for a gain less than 10. The output
impedance is also low being in the range of milliohms.
The input bias current of the instrumentation amplifier is
determined by that of the amplifiers A1 and A2.
Features
The important features of an instrumentation amplifier are
1. High gain accuracy and linearity
2. High CMRR
3. High gain stability with low temperature coefficient.
4. Low dc offset
5. Low output impedance
The instrumentation amplifier is also called as Data
amplifier.
The expression for its voltage gain is generally of the form,
A = (V0/V2) – V1
Where V0 = output of the amplifier
V2-V1 = differential input is to be amplified.
Requirements of a good instrumentation amplifier
1. Finite, accurate and stable gain
2. Easier gain adjustment
3. High input impedance
4. Low output impedance
5. High CMRR
6. Low power consumption
7. Low thermal and time drift
8. High Slew rate
89

PROCEDURE
1. Switch ON the Instrumentation amplifier unit. Switch SW1 should be
in internal mode.
2. Select the gain of 10 i.e, Switch SW2 should be in R1 mode.
3. Connect the multimeter in millivolt mode across the T1 and T2.
4. Calibrate the unit by using the mV source POT and zero adjustment
POT.
5. When input is zero, display voltages are brought to zero by varying
the zero adjustment POT.
6. After the completion of the calibration, start the experiments.
7. Set the input (say 40 mV) by varying the mV source POT.
8. Measure the output voltage across T5 and GND or from the display.
9. Analyse the output for various input signal.
Design
An analysis of the circuit gives the following equation:
Let R1 = R2 = R3 = R4
Considering the basic differential amplifier shown below, the
output voltage V0 is given by
V0 = - R2/ R1 V2 + 1/1 + R3/R4 V1(1+ R2/R1)
Or,
V0 = R2/ R1 (V2 – 1/1 + R3/R4 (R1/ R2+1)V1V1)
V0 = -R2/R1 V2 + 1/ 1+R3/R4 V1 (1+ R2/R1)
89
V0 = -Rf / Rin (V1 –
V2)

1. What is the need of instrumentation amplifier?
The low level signal outputs of electrical transducers often
need to be amplified before further processing. This is done
by the use of instrumentation amplifier.
2. What are the advantages of instrumentation amplifier?
It has low level signal amplification, low noise, low thermal
and time Drifts, high common-mode rejection ratio and
high slew rate.
3. What are the applications of Op-Amp?
The applications are categorized as linear applications,
filter and oscillator applications, comparator and detector
applications, special integrated circuit applications and
selected system applications.
4. State some linear applications of Op-Amp?
In linear circuits, the output signal varies with the input
signal in linear manner. The linear applications are adder,
subtractor, Instrumentation amplifier, power amplifier, V-I
converter, I-V converter, analog computation, power amplifier
etc.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus an instrumentation amplifier was studied.
89

CIRCUIT DIAGRAM
A/D CONVERTER
89
Control
& Timer
SAR
SWITCH
TREE
256 R-2R
Ladder
Network
VCC
GND
Address
latch
buffer
8 CHANNEL
MUX
ANALOG
SWITCHES
Comparato
r
+
-
STATE
OUTPUT
LATCH
BUFFER
Ref
(+)
)
Ref (-)
)
SW1
SW2
SW3
Channel
8 Bit Output

Exp.No:
Date:
A/D CONVERTER AND D/A CONVERTER
AIM
To design and test a four bit A/D converter and D/A converter.
REFERENCE
and
Basic theory and operation of A/D and D/A and its types
APPARATUS REQUIRED
1 A/D converter, D/A
converter Trainer kit
- 1
2 CRO with probe - 1
3 1 K potentiometer to vary
the input signal
- 1
THEORY
DIGITAL TO ANALOG CONVERSION
It involves conversion of digital information into equivalent analog
information. Digital to analog converter (DAC) acts as a decoding device
since it operates on the output of the system. DAC are of two types,
Binary weighted resistor type & R-2R ladder type.
R-2R ladder DAC:
In this type, the reference voltage is applied to one of the switch
position and the other switch position is connected to ground. The typical
values of resistors range from 2.5kΩ to 10kΩ. Let us consider 3 bit R-2R
ladder DAC with binary input 001. The output voltage will be VR/ 8, is
equivalent to binary input 001.
ANALOG TO DIGITAL CONVERSION
The analog information is converted into equivalent binary number
in the digital form. Analog to digital converter (ADC) acts as an encoder.
The types of ADCs are 1) single slope, 2) Dual slope, 3) successive
approximation, 4) Flash type, 5) Delta modulation and 6) Adaptive delta
modulation. In this type most frequently used method is successive
approximation.
Successive approximation:
In this type the basic idea is to adjust the DAC’s input code such
that its output is within ±1/2 LSB of the analog input VI. The circuit uses
Successive Approximation Register (SAR) to find the required values of
each bit by trial and error.
89

D/A CONVERTER
89
R
2R
R
Rf
2R2R
2R
-
+
DIGITAL INPUT
LSBMSB
5 6 7 8 9 10 11 12
5K
5K
10K 10K
10V
IOUT
VOUT
GND
3 16
0.1μF
0.1μF
0.01μF
113
10V
V+V-

PROCEDURE
D/A Converter
1. Switch on the Power supply.
2. The jumpers J9 to J16 should be in the s/w (right) position.
3. The switches sw1 through sw8 are placed approximately to
represent the desired output.
4. For example if the input is 4.96v then the switch positions are
as follows.
SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 Hex
Value
1 1 1 1 1 1 1 0 FEh
5. The output voltage can be observed by using CRO at the
terminal pin P2
A/D Converter
1. The power supply is Switched on .
2. The Variable terminal of the potentiometer is given to analog
input channel 2.
3. To select the analog input channel 2, the channel select switch
position is as follows.
4. The start of conversion (soc) button is pressed. Once to start the
Conversion from analog signal to digital form. The LED 9 glows on
pressing start of
Conversion button.
5. The Address latch enable (ALE) button is also pressed once, so as
to enable the digital data to be sent to the output.
6. The digital output for the corresponding analog input is displayed
on the LED’s do through D7. For analog input of 4.92V, the digital
output is given as.
D7 D6 D5 D4 D3 D2 D1 D0 Hex
Value
1 1 1 1 1 1 0 1 EE
7. The end of conversion is indicated by the LED L10.
8. The procedure is repeated for different values of analog voltage.
89
SW1 SW2 SW3
0 1 0

TABULATION
Digital to Analog Conversion
Sl.
No
B7 B6 B5 B4 B3 B2 B1 B0
Hex
Value
Analog
O/p
Analog to digital Conversion
Sl.
No
Analo
g
I/p
B7 B6 B5 B4 B3 B2 B1 B0
Hex
Value
89

DISCUSSION QUESTION
1. What are the types of D/A converter?
• Binary weighted resistor type
• R-2R ladder type.
2. What are the advantages of R-2R ladder D/A
converter?
The number of bits can be expanded by adding more section of
same R-2R values. It is easier to build accurately as only two
precision metal film resistors are required
3. What are the uses of D/A converter?
D/A converter are used in computer drives, CRT displays, digital
generation of analog of analog waveforms and digital control of
automatic process control systems
4. What are the types of A/D conversion?
• Successive approximation method
• Voltage to time conversion method
• Voltage to frequency conversion method
• Dual slope integration method
5. What is the use of A/D conversion device?
The data to be fed to digital devices normally appears in analog
form. Therefore analog to digital conversion devices are used
where digital output is needed.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the analog output voltage from digital input and digital
output from analog input were obtained.
89

Exp.No:
Date:
STUDY OF TRANSIENTS
AIM
To study the transients of DC circuits and AC circuits.
REFERENCE
1. M.Arumugam and N.Prem Kumar – Electrical circuits Theory,
Khanna Publishers, Newdelhi.
2. B.L. Theraja – Fundamentals of Electrical and Electronics,
S.Chand and Company Ltd, New delhi.
• Basic concepts of DC and AC circuits
• Basic concepts of RL, RC and RLC transients
THEORY
Transient phenomenon is a periodic function of time and
doesn’t last longer. The duration of which they last is very significant
as compared with operating time of the system. But they are very
important because depending upon the reversibility of the transients,
the system may result in blocked condition.
REQUIREMENT OF TRANSIENT IN THE CIRCUIT
1. Either inductor or capacitor or both should be present.
2. A sudden change in the parameter as the form should occurs as a
fault or any switching operation.
a) The following are the simple 3 facts which are the fundamental to
the phenomenon of transients in electrical power systems.
b) The current can’t change instantaneously through any inductor.
c) The voltage across a capacitor can’t change instantaneously.
3. The law of conversion of energy should hold good.
DC TRANSIENT RESPONSE OF RLC CIRCUIT
The resistance, inductance and capacitance are connected in series.
The capacitor and inductor are initially unchanged and are in series
with the resistor. When switch is closed at t=0, we can determine the
complete solution for current.
89

Applying KVL,
V=iR+Ldi/dt +1/C∫idt
Differentiating above equation
WORK SHEET
89

0=Rdi/dt+Ld²i/dt²+(1/C)i
It is a second order differential equation,
D²+(R/L)D+1/LC=0
The roots are
Dı,D2=-(R/2L)± [(R/2L)²-1/LC]½
By assuming,
Kı=R/2L, K2=[(R/2L)²-1/LC]½
Dı=Kı+K2, D2=Kı-K2
Here,K2 may be positive, negative or zero
K2 is positive when (R/2L)²>1/LC
The roots are real and unequal and give the overdamp response
[D-(Kı+K2)][D-(Kı-K2)]i=0
The solution is i=cıе^(Kı+K2)t+ c2е^(Kı-K2)t
K2 is negative when (R/2L)²<1/LC
The roots are complex conjugate and give the underdamped
response
[Dı-(Kı-jK2)][D2-(Kı-jK2)]=0
Solution is given by
i=е^(Kı*t)[cıcos K2+c2sin K2t]
K2 is zero,where (R/2L)²=1/LC
Solution is given by i=е^Kı+(Cı+C2)t
SINUSOIDAL RESPONSE OF RLC CIRCUIT
Switch ‘S’ is closed at t=0,a sinusoidal voltage V(cosωt+θ) is
applied to RLC series circuit where V=amplitude of the wave,
θ=phase angle.
Applying the KVL,
89

V(cosωt+θ)=Rı+Ldi/dt +1/C∫idt
Differentiating the above equation,
Rdi/dt+Ld²i/dt²+i/C=-Vωsin(ωt+θ)
[ D²+(R/L)D +(1/LC)]i=-(Vω/L)(sinωt+θ)
WORK SHEET
89

solving above equation, we get
ip=[Vω²(R/L²)*cos(ωt+θ)]/[(ωR/L)² -(ω²-1/LC)²] + [(ω²-1/LC)
{Vmsin(ωt+θ)}]/L[((ωR/L)²-(ω²-1/LC)²]
TO FIND M & ø
Msin ø/Mcos ø=tan ø=[ωL-(1/ωC)]/R
ø=–tanˉ¹ [ωL-(1/ωC)]/R
Squaring both equations
M²cos ²ø+ M²sin ²ø=V²/R²[(1/ωc-1/ωL)²]
ip=V/[R²+(1/ωc-ωL)²]½ cos [ωt+θ –tanˉ¹{(1/ωc-ωL)/R}]
Dı,D2=-(R/2L)± [(R/2L)²-1/LC]½
Dı=Kı+K2, D2=Kı-K2
K2 is positive when (R/2L)²>1/LC
ic= е^(Kı*t)[cıcos K2t+c2sin K2t]+V/[R²+(1/ωc-ωL)²] *cos[ωt+θ –
tanˉ¹(1/ωc-ωL)²]
ic= [е^(Kı*t)]*(cı+c2)t
i= е^(Kı*t)(cı+c2)t+ V/[R²+(1/ωc-ωL)²]½ *cos[ωt+θ +tanˉ¹(1/ωcR-
ω/R)²]
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the transient in DC and AC circuit for an RLC circuit is
studied.
89

Exp.No:
Date:
CALIBRATION OF SINGLE-PHASE ENERGY METER
AIM
To calibrate the given single-phase energy meter by direct
loading .
REFERENCE
Measurements and Instrumentation, Dhanpat Rai & Sons, 1984.
APPARATUS REQUIRED
Sl.N
o
Apparatus Range
Type Quanti
ty
1 Voltmeter (0-300V) MI 1 No.
2 Ammeter (0-10A) MI 1 No.
3 Wattmeter 300V,10A UPF 1 No.
4 Test energy meter
1Ø,230V,5-
30A
-
1 No.
5 Connecting wires
- - Require
d
THEORY
89

Direct loading
In this method, precision grade indicating instruments are used
as reference standard. These indicating instruments are connected in
the circuit of meters under test. The current and voltage are held
constant during the load test. The number of revolutions made by the
meter disc and the time taken during the test are recorded.
89

PRECAUTIONS
i. Auto transformer is kept at minimum position at the time of starting.
ii. Rheostat is kept at minimum position in phantom loading.
iii. Phase shift transformer is kept at UPF position
PROCEDURE
Direct loading
1. Make the circuit connection as per the circuit diagram.
2. Close the DPST switch.
3. Adjust single phase auto transformer till the voltage connected across
the primary winding reads rated primary voltage.
4. Vary the resistive load to vary the load current.
5. Note down readings of time taken for the Energy meter for 5
revolutions, Wattmeter, ammeter and voltmeter.
6. Repeat the same procedure for various load conditions.
7. Calculate percentage error and draw the graph between percentage
error and load current.
FORMULAE
% 100%
Actual Trueenergy
Error
Actualenergy
−
= ×
100%
3600 1000
No. of revolution made by energy meter
Actual energy =
meter constant
Wattmeter reading Timetaken
True energyinkWhr
×
= ×
×
89

TABULATION
Direct loading
Sl.No
.
Voltag
e
(Volts)
Curre
nt
(Amps
)
Wattmet
er
Reading
(Watts)
Time
taken for
5
revolutio
ns
Actual
Energ
y
True
energ
y
%Erro
r
MODELGRAPH
89

1. What is creeping in energy meter?
It is a slow continuous rotation, when there is no current flows through
the current coil and only pressure coil is energized. This behavior is
called creeping.
2. What is the provision available in energy meter for adjusting
creeping?
(i)Two diametrically opposite holes are drilled in disc.
A small piece of iron is attached to the edge of the disc. The force of
attraction exerted by the brake magnet on the iron piece varies the
creeping.
3. What are the provisions available in low power factor
measurement energy meter?
(i) Adjustable resistance (ii) shading bands
4. What is calibration and why is it needed for instruments?
It is the procedure for determining the correct value of measured
quantity by comparison with the standard one. In order to determine
the standards of the instrument , it should be calibrated.
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the single phase energy meter was calibrated using direct loading
method.
89

CIRCUIT DIAGRAM
Star Connected Load
89
W2
400 Ω / 2A
M L
C V
R
B
440 V
3
50 Hz
AC
Suppl
y
T
P
S
T
S
Y
V
A
M L
C
V
W1
V
400 Ω / 2A
400 Ω / 2A
N

Exp.No:
Date:
MEASUREMENT OF THREE-PHASE POWER AND POWER FACTOR
AIM
To measure the power and power factor in three-phase circuit star
connected,
Delta connected load & to check the relationship between line and
phase quantity.
REFERENCE
and
1. Basics of three-phase power and power factor
2. Basics of Star and Delta connections.
APPARATUS REQUIRED
Sl.N
o
Apparatus Range
Type Quantit
y
1 Voltmeter (0-600V) MI 1
2 Ammeter (0-10A) MI 1
3 Wattmeter 600V,10A UPF 1
4 Rheostat 5 KW - 1
5 Connecting wires - - Required
THEORY
In a three phase, three wire system, we require three elements. But
if we make the common points of the pressure coils coincide with one of the
89

lines, then we require only two elements. Instantaneous power consumed by
load =V1i1+V2i2+V3i3
89

Star Connection
Instantaneous reading of wattmeter is P1 and the instantaneous
reading ofW2 is P2.Sum of instantaneous readings of two wattmeters
=P1+P2.Sum of instantaneous readings of two wattmeter =
V1i1+V2i2+V3i3.Therefore, the sum of the two wattmeter reading is equal
to the power consumed by the load. This is irrespective of whether the
load is balanced or unbalanced.
Delta Connection
Here, by means of Kirchoff’s voltage law, sum of instantaneous
readings of two wattmeter = V1i1+V2i2+V3i3.Therefore the sum of the
two wattmeter readings is equal to the power consumed by the load.
This is irrespective of whether the load is balanced or unbalanced.
Total power consumed by load = P1 +P2.
Power factor, cosΦ = cos [tan-1
3 ( P1 -P2)/ ( P1 +P2.)]
With unity power factor, P1= P2= (3/2) VI
With 0.5 power factor, P1= (3/2) VI, P2=0.
With zero power factor, P1= 3 /2VI& P2= (- 3 /2) VI
FORMULAE
3 cosL LPower V I φ= (Watts)
where,
VL = Line voltage (Volts)
IL = Line current (Amps)
cosφ = Power factor
cosφ = / 3 L LPower V I
For Star connected load, For Delta connected load,
IL = Iph, IL = 3 Iph,
VL= 3 Vph, VL= Vph,
PROCEDURE
1. Make the circuit connection as per the circuit diagram.
2. Close the TPST switch.
3. Note down the Wattmeter readings W1 and W2.
4. know the Multiplication factor, calculate the power.
5. Note down the line voltage and phase voltage using voltmeters.
6. Note down the line current and phase current using ammeters.
7. By using the above readings calculate the power and power
factor
89

TABULATION
M.F=
Type of
Connectio
n
Voltage (V)
Current
(I)
Wattmeter
reading
Power
factor
cosφVph
(V)
VL
(V)
Iph
(A)
IL (A)
W1
(W)
W2
(W)
Star
Delta
MODEL CALCULATION
89

1. What do you mean by power factor?
The cosine of phase angle between the voltage and current is
called the power factor
2. What are the methods for measuring power?
a. The methods for measuring power are
b. (i)Single wattmeter method (ii) Two wattmeter method and
(iii) Three Wattmeter method
3. What is the relation between the line and phase
quantities in delta connection?
VL=VPH, IL= 3 IPH
Where, IL = Line current
V L = Line voltage , VPH = Phase voltage
IPH = Phase current
4. What are the advantages of three phase system?
i. Three phase transmission line requires less
number of conductor material than single phase line for
transmitting the same amount of power and voltage.
ii. Parallel operation is simple & power factor is high.
iii. Cost wise per unit of output in three phase machine
is very much cheaper.
5. What is energy?
Energy is the total power delivered or consumed over a time
interval. Its unit is Kilowatt hour (KWH).
Performance 25
Record 15
Viva voce 10
Total 50
RESULT
Thus the relationship between phase & line quantities for star
and delta connected loads are verified in three phase connection.
CIRCUIT DIAGRAM
89

CURRENT TRANSFORMER
Loading
Rheostat
P
Ammeter
Voltmeter
N
Current Transformer
89
V
A
V
30 V
AC
Suppl
y

Exp.No:
Date:
CALIBRATION OF CURRENT TRANSFORMER
AIM
To study and calibrate current transformer parameters and to
draw the curve primary current and Vs Secondary current.
REFERENCE
Measurements and
Principle of working of current transformer
APPARATUS REQUIRED
S.N
o
Name of the Apparatus Range Quantity
1
Current Transformer
Trainer kit
-
1
2 Rheostat 500 Ω,3A 1
3 Loading rheostat 5 kW 1
4 Patch cords - 1
FORMULAE
Ratio error or Current error (%) = 100( KN IS -IP)
IP
KN = Primary winding current
Secondary winding current
Phase Angle error ө =
m180 I
pIπ
   
      
Im =
p
s
I
nI
 
  
89

TABULAR COLUMN
S No Supply
Voltage
(V)
Primary
Current
( IP)
Secondary
Current
( IS)
Ratio
Error
KN
Phase angle Error
ө
89

THEORY
A current transformer is an instrument transformer specially
designed and assembled to be used in measurement control and
protective circuits. Its primary consists of few turns and is connected
in series with the circuit whose current is desired to be measured and
the secondary is connected to the current measuring instrument.
The secondary circuit is closed through the typical low
impedance of the instruments connected to it. These are 5 A
instruments. The voltage across secondary is the drop through the
instruments and loads and usually is only 5 volts.
In ideal CT, the secondary current is inversely proportional to the
ratio of turns and opposite in phase to the impresses primary current.
The exciting current must be subtracted phasorially from the primary
current to find the amount remaining to supply Secondary current. This
value will be slightly different from the value that the ratio of turns
would indicate and there is slight shift in phase relationship. This
results in introduction of ratio and phase angle errors when compared
to ideal CT.
PROCEDURE
The calibration of current transformer operation is under two
modes (ie.Low voltage and high voltage)
Low Voltage: (ie.30 V)
1. Connect the circuit as per the circuit diagram
2. Switch on the kit with rheostat at minimum position.
3. Load the CT by using 500 Ω, 3A rheostat.
4. Now note down the primary ( IP) and secondary current ( IS) of the
transformer.
5. Tabulate the readings and calculate calibration parameters.
High Voltage: (ie.230 V)
1. Connect the circuit as per the circuit diagram
2. Switch on the kit and switch on the MCB.
3. Keep the rheostat in the maximum position.
4. Load the CT by using loading rheostat 5k W.
5. Now note down the primary ( IP) and secondary current ( IS) of
transformer.
6. Tabulate the readings and calculate calibration parameters
89

1. Define current transformer.
A current transformer (CT) is a type of instrument
transformer designed to provide a current in its secondary winding
proportional to the alternating current flowing in its primary.
2. How is current transformer designed?
The most common design of CT consists of a length of wire
wrapped many times around a silicon steel ring passed over the circuit
being measured. The CT's primary circuit therefore consists of a single
'turn' of conductor, with a secondary of many hundreds of turns.
Common secondaries are 1 or 5 amperes.
3. Mention uses of current transformer.
Current transformers are used extensively for measuring current
and monitoring the operation of the power grid. The CT is typically
described by its current ratio from primary to secondary. Often,
multiple CTs are installed as a "stack" for various uses (for example,
protection devices and revenue metering may use separate CTs).
4. Mention precautions to be followed while using current
transformer.
Care must be taken that the secondary of a current transformer
is not disconnected from its load while current is flowing in the
primary, as this will produce a dangerously high voltage across the
open secondary, and may permanently affect the accuracy of the
transformer.
5. What is calibration? Mention the need for calibration.
Calibration is a measurement process that assigns values to the
response of an instrument relative to reference standards or to a
designated measurement process. The purpose of calibration is to
eliminate or reduce bias in the user's measurement system relative to
the reference base. The calibration procedure compares an "unknown"
or test item(s) or instrument with reference standards according to a
specific algorithm.
6. Mention calibrated parameters of current transformer
Ratio error and Phase Angle error
Performance 25
Record 15
Viva voce 10
Total 50
89

RESULT
Thus the given current transformer was calibrated. The
Calibrated parameters
are ratio error & phase angle error
and the primary Vs Secondary current was drawn.
Exp.No:
Date:
MEASUREMENT OF IRON LOSS
AIM:
An Ac bridge method is employed for measurement of core
losses in ferromagnetic material
THEORY:
Any bridge capable of measuring the impedance of any iron core
coil could be used for this.
The Maxwell’s wein bridge circuit or Maxwell’s inductance
capacitance bridge is used for the measurement of core loss.
La = unknown inductance.
Rd = effective resistance of inductance.
Ra, Rb, Rc = known iron – inductance resistance.
Cb = variable standard capacitor.
Rb
(Rd+j wld) [ ] = Ra Rc (or) Z 1 Z4
= Z3 Z2
I+jwCbRb
Ra Rb + j w L d =Ra Rc + j w Ra Rc Cb Rb
In order to use this bridge circuit for the measurement of power
loss, the primary of the test frame is connected in bridge. The
maximum flux density is calculated by
Eqvg = 4 f B max NA x 10-6
Where
Eqvg = average absolute value of abc voltage.
F = frequency.
Bmax = max flux density
N = numbers of turns
A = cross sec area of ferromagnetic specimen.
89

Balance at fundamental frequency is obtained by adjusting Rb + cb so
that the deletor indicates.
If the induction in ferromagnetic specimen is low and if the o/p
voltage of power source has a negligible amount of
WORK SHEET
89

Exp.No:
Date:
MEASUREMENT OF IRON LOSS
AIM:
To measure and study the iron loss of given ring specimen.
APPARATUS REQUIRED
S.N
o
Name of the Apparatus Range Quantity
1
Iron loss measurement
trainer kit
-
1
2 Digital multimeter - 1
3 Microphone - 1
4 Patch chords - 1
THEORY:
Any bridge capable of measuring the impedance of any iron core
coil could be used for this.
The Maxwell’s wein bridge circuit or Maxwell’s inductance
capacitance bridge is used for the measurement of core loss.
La = unknown inductance.
Rd = effective resistance of inductance.
Ra, Rb, Rc = known iron – inductance resistance.
Cb = variable standard capacitor.
Rb
(Rd+j wld) [ ] = Ra Rc (or) Z 1 Z4
= Z3 Z2
I+jwCbRb
Ra Rb + j w L d =Ra Rc + j w Ra Rc Cb Rb
89

In order to use this bridge circuit for the measurement of power
loss, the primary of the test frame is connected in bridge. The
maximum flux density is calculated by
Eqvg = 4 f B max NA x 10-6
Where
Eqvg = average absolute value of abc voltage.
F = frequency.
Bmax = max flux density
N = numbers of turns
A = cross sec area of ferromagnetic specimen.
Balance at fundamental frequency is obtained by adjusting Rb + cb
so that the deletors indicate.
FORMULA:
At balance condition:
Unknown Resistance
RS = Std. R1 x Std.R3 x C
For the value of R3 select Std. Resistance according to the specimen’s
inductance. Say low value of inductance in specimen needs a lower
value of std.r3. In our unit the Std. resistance R3 values to be chosen
are 10Ω/100Ω/1KΩ.
Unknown Resistance
RS = Std. R1 x Std.R3
R3
Where:
R2 – Std. Resistance measured by using multimeter across pot2.
Iron loss = IL
2
x (RS – R W)
Where:
I1 – Current floe to the specimen in ampere (A).
RS Specimen Resistance.
RW Winding Resistance (measure by using multimeter)
C – Std. Capacitor (0.1µF)
PROCEDURE:
89

1. Connections are made as per the connection diagram fig 1.
2. Connect the ring specimen to the bridge arm, for which
measurement to be made.
3. Keep the POT 2 in maximum position and switch on the unit.
4. The output can be detected either by microphone (or) CRO /
multimeter.
5. For detecting the output vary the POT 1 from lower to higher
value. At one stage the output goes to minimum value. (ie,
bridge become balanced or current flow through detector is zero
(or) minimum.
6. Now note down the Resistance of the POT 1 by using multimeter.
7. In this condition note down the A.CX current though ring
specimen (I1), value of POT 1 and the Source current by using
milli ammeter (2 or 200mA range selection).
8. Substitute these values in an approximated formula and find out
the iron loss of the given ring specimen.
9. Similarly repeat the same procedure for the given three ring
specimens.
RESULT:
The iron loss of the given ring specimen is measured.
89
Performance 25
Record 15
Viva voce 10
Total 50

TABULAR COLUMN
SL.N
o
Inductance (LS )in mH Resistanc
e (RS) in
ohms
Current
(I1) in mA
(AC)
Iron Loss
Theoretical
value
Practical
value
89

CIRCUIT DIAGRAM
SINGLE PHASE ENERGY METER
89

47512039 m-i-lab-manual

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