Download Maharashtra Institute Of Technology, Aurangabad LABORATORY

Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : V-I characteristics of p-n junction Diode.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 1
Aim: Study of characteristics of Silicon diode in :
1. Forward bias
2. Reverse bias
Apparatus:
1. Analog board of AB01.
2. DC power supplies +12V from external source or ST2612 Analog Lab.
3. Digital Multimeter (2 numbers).
Circuit diagram :
Circuit used to plot different characteristics of Si diode is shown in figure:
Theory:
Introduction :
A diode is an electrical device allowing current to move through it in one direction with far greater
ease than in the other. The most common type of diode in modem circuit design is the
semiconductor diode, although other diode technologies exist. Semiconductor diodes are
symbolized in schematic diagrams as shown below.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : V-I characteristics of p-n junction Diode.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 2
When placed in a simple battery-lamp circuit, the diode will either allow or prevent current through
the lamp, depending on the polarity of the applied voltage
When the polarity of the battery is such that electrons are made to flow through the diode, the diode
is said to be forward-biased. Conversely, when the battery is "backward" and the diode blocks
current, the diode is said to be reverse biased. A diode may be thought of as a kind of switch:
"closed" when forward-biased and "open" when reverse-biased.
V-I Characteristic :
The static voltage-current characteristics for a P-N Junction diode are shown in figure
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : V-I characteristics of p-n junction Diode.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Forward Characteristic :
When the diode is in forward-biased and the applied voltage is increased from zero, hardly any
current flows through the device in the beginning. It is so because the external voltage is being
opposed by the internal barrier voltage VB whose value is 0.7V for Si and 0.3V for Ge. As soon as
VB is neutralized, current through the diode increases rapidly with increasing applied supply
voltage. It is found that as a little voltage of 1.0V produces a forward current of about 50mA.
Reverse Characteristic :
When the diode is reverse-biased, majority carrier are blocked and only a small current (due to
minority carrier) flows through the diode. As the reverse voltage is increased from zero, the reverse
current very quickly reaches its maximum or saturation value Io which is also known as leakage
current. It is of the order of nanoAmperes (nA) and microAmperes (mA) for Ge. As seen from
figure , when reverse voltage exceeds a certain value called breakdown voltage VBR, the leakage
current suddenly and sharply increases, the curve indicating zero resistance at this point.
Procedure :
· Connect +12V DC power supplies at their indicated position from external source or ST2612
Analog Lab.
· To plot forward characteristics proceed as follows
1. Rotate potentiometer P1 fully in CCW (counter clockwise direction).
2. Connect Ammeter between test point 2 and 8 to measure diode current ID (mA).
3. Connect one voltmeter between test point 1 and 9 to measure voltage VD diode
4. Switch ‘On’ the power supply.
5. Vary the potentiometer P1 so as to increase the value of diode voltage V D from zero to 1V in
step and measure the corresponding values of diode current ID in an observation Table 1.
6. Plot a curve between diode voltage VD and diode current ID as shown in figure (First quadrant)
using suitable scale with the help of observation Table 1. This curve is the required forward
characteristics of Si diode.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : V-I characteristics of p-n junction Diode.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 4
Observation Table No.1
Sr.No.
Diode
Voltage(VD)
1
0.0V
2
0.1V
3
0.2V
4
0.3V
5
0.4V
6
0.5V
7
0.6V
8
0.7V
9
0.8V
10
0.9V
11
1.0V
Diode Current
ID(mA)
To plot Reverse characteristics of a Si diode proceed as follows
1. Rotate potentiometer P1 fully in CCW (counter clockwise direction).
2. Connect Ammeter between test point 3 and 8 to measure diode current ID (nA).
3. Connect one voltmeter between test point 1 and 9 to measure voltage VD diode
4. Switch ‘On’ the power supply.
5. Vary the potentiometer P1 so as to increase the value of diode voltage V D from zero to 10V in
step and measure the corresponding values of diode current ID in an observation Table 2
6. Plot a curve between diode voltage VD and diode current ID as shown in figure (third quadrant)
using suitable scale with the help of observation Table 2. This curve is the required forward
characteristics of Si diode.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : V-I characteristics of p-n junction Diode.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Observation Table No.2
Sr.No.
Diode
Voltage(VD)
1
0.0V
2
1V
3
2V
4
3V
5
4V
6
5V
7
6V
8
7V
9
8V
10
9V
11
10V
Diode Current
ID(nA)
Conclusion:
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Page 5
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Study of Half Wave Rectifier
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim: To study Half wave Rectifier Circuit.
Apparatus:
1. Analog board of AB09.
2. AC power supplies of 0-9Vrms from external source or ST2612 Analog Lab.
3. Oscilloscope.
4. 2 mm patch cords.
Circuit diagram :
Circuit used to study the Half wave Rectifier is shown in figure :
Theory:
Rectifier is an electronic device that converts alternating current into direct current. A rectifier
changes AC into DC by eliminating the negative half-cycles of the alternating voltage, so it
provides a one way path for electric current i.e. conduction takes place in one direction only. It is in
this way that a rectifier converts an alternating current into unidirectional current.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Study of Half Wave Rectifier
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Rectifier can be classified into two categories:
1. Half-wave rectifier
2. Full-wave rectifier
Half wave rectifier conducts only on positive half cycles of input voltages i.e. it uses one half
cycles of AC input voltages to produce DC output .On the other hand, a full wave rectifier conducts
on both the half cycles of input AC voltage to produce DC output. So a full wave rectifier circuit
can supply more DC output more than the equivalent half-wave rectifier.
Half wave Rectifier :
A half wave rectifier employs a single diode as shown in figure
During the positive half cycle of the input voltage diode conducts, so a short circuit equivalence of
the ideal diode will result in an output signal which is an exact replica of the input signal. For the
negative half cycle of the applied signal diode is in the off state with an open circuit equivalent,
which results in the absence of a path for the charge to flow, so a zero voltage appears for the
negative half cycle of input voltage.
Vdc = .318 Vm
Limitation of Half wave Rectifier :
The AC power delivers only half the time, hence output is low.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Study of Half Wave Rectifier
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Important parameters for rectifier circuits :
Peak inverse voltage :
The maximum reverse-bias potential that can be applied to a diode before entering the Zener region
is called peak inverse voltage or peak reverse voltage.
Half wave Rectifier PIV rating ≥ Vm
Center tap Full wave Rectifier PIV rating ≥ 2Vm
Full wave Bridge Rectifier PIV rating ≥ Vm
Rectification efficiency :
The ratio of DC output power to the AC power input in a rectifier is known as rectification
efficiency.
Efficiency of Half wave rectifier :
is diode resistance
Efficiency of Full wave rectifier (Center tap and Bridge Rectifiers) :
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : Study of Half Wave Rectifier
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Ripple factor :
The ratio of r.m.s. value of AC component to the DC component in the rectifier output is known as
ripple factor. The smaller the ripple factor, the lesser the effective AC component and hence more
effective is the rectifier.
Mathematical analysis
Half wave rectification :
Putting values in eq.3 we get
Ripple Factor=1.21
Procedure :
Connect 0-9Vrms from ST2612 Analog Lab or from Analog Digital Lab Power Supply or from
any external source (transformer o/p or function generator) to sockets m and c of AB09 Board
respectively using 2mm patch cords.
1. Connect 2mm patch cord between sockets e and j. This will connect load resistance RL across the
output of half wave rectifier.
2. Connect Ch I of oscilloscope between sockets i and n and observe the half wave rectified o/p
waveform across the load resistor (keep AC/DC push button switch of oscilloscope in AC position)
3. Measure the output DC voltage by pressing the AC/DC push button switch of the oscilloscope or
by connecting a digital multimeter across sockets j and n i.e. across load resistance and carry out
following calculations.
4. Now connect the 2mm patch cord between i and l socket. This will connect the filter capacitor
across the o/p of half wave rectifier.
5. Observe the filtered output on oscilloscope.
Results :
1. Output voltage Vo =…………………………………..
2. Efficiency (using eq.1) = ………………………………
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Drain Characteristics of JFET
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim:- Drain characteristic of JFET
Apparatus:1. Analog board of AB08.
2. DC power supplies +12V,-5V from external source or ST2612 Analog Lab.
3. Digital Multimeter (3 numbers).
4. 2 mm patch cords.
Theory:FET is a voltage controlled current device so its characteristics are the curves which
represent relationship between different DC currents and voltages. These are helpful in studying
different region of operation of a Field effect transistor when connected in a circuit. The two
important characteristics of a Field Effect Transistor are:
1. Output /Drain characteristic.
2. Transfer characteristic.
Output / Drain Characteristics:
It is the curve plotted between output drain current ID versus output drain to source voltage VDS
for constant values of input Gate to source voltage VGS as shown in figure 1.
Figure 1
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Drain Characteristics of JFET
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Figure 2
Transfer Characteristic :
It is the curve plotted between output drain current versus input Gate to source voltage
for constant values of output drain to source voltage as shown in figure 3.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Page 3
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Drain Characteristics of JFET
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
It is similar to the transconductance characteristics of a vacuum tube or a transistor. It shows that
when VGS = 0, ID = IDSS and when ID = 0, VGS = VPO. The transfer characteristic
approximately follows the equation
ID = IDSS [1 − (VGS / VPO)2] = IDSS [ 1 − (VGS / VGS(off))2 ]
The above equation can be written as VGS = VGS (off) [1 − (ID / IDSS)1/2 ] These characteristics
can also be obtained from the drain/output characteristics by reading off VGS and IDSS values for
different values of VDS. The various parameters of a JFET can be obtained from its two
characteristics. The main parameters of a JFET when connected in common source mode are
AC Drain Resistance, rd:
It is the AC resistance between drain and source terminals when JFET is operating in the pinch-off
region. It is given by
rd = change in VDS
change in ID
at VGS constant or rd = VDS / ID | VGS
An alternative name is dynamic drain resistance. It is given by the slope of the drain characteristics
in the pinch off region. It is sometimes written as rds emphasizing the fact that it is the resistance
from drain to source. Since rd is usually the output resistance of a JFET, it may also be expressed
as an output admittance yos. Obviously, yos = 1/rd. It has a very high value.
Transconductance, gm:
It is simply the slope of transfer characteristics
gm = change in ID
at VDS constant or rd = ID / VGS | VDS
Change in VGS
Its unit is siemens (S) /Mho. It is also called forward transconductance (gfs) or forward
transadmittance Yfs. The transconductance measured at IDSS is written as gmo. Mathematically
gm = gmo [1− (VGS / VP)]
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Drain Characteristics of JFET
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Amplification factor, µ:
It is given by
µ = change in VDS
at ID constant or µ = VDS / VGS | IDS
change in VGS
It can be proved from above that µ = gm × rd = gfs × rd
DC drain resistance, RDS:
It is also called the static or ohmic resistance of the channel. It is given by
RDS = VDS / ID
Circuit diagram :
Circuit used to plot different characteristics of transistor is shown in figure 4.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Page 3
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Drain Characteristics of JFET
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Procedure :
1. Connect -5V and + 12V DC power supplies at there indicated position from
external source or ST2612 Analog Lab.
2. To plot Drain characteristics proceed as follows :
3. Rotate both the potentiometer P1 and P2 fully in counter clockwise direction.
4. Connect Ammeter between test point 3 and 4 to measure output drain current ID
(mA).
5. Connect one voltmeter between test point 1 and ground to measure input voltage
VGS other voltmeter between test point 2 and ground to measure output voltage
VDS.
6. Switch ‘On’ the power supply.
7. Vary the potentiometer P2 so as to increase the value of output voltage VDS from
zero to 10V in step and measure the corresponding values of output drain
current ID for different constant value of output voltage VDS in an observation
table 1.
8. Rotate potentiometer P2 fully in Counter Clockwise direction.
9. Rotate potentiometer P1 and set the value of input gate to source voltage at some
constant value (-1V, -2V, -3V……….)
10. Repeat the procedure from step 6 for different sets of input voltage VGS.
11. Plot a curve between output voltage VDS and output current ID at different
constant values of input gate to source voltage as shown in figure 2 using
suitable scale with the help of observation table 1. This curve is the required
output/Drain characteristic.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Page 3
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : To study the Bourdon tube.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim:- To study the Bourdon tube.
Theory:Basic Principle of Bourdon tube pressure gauge:
when an elastic transducer ( bourdon tube in this case ) is subjected to a pressure, it defects. This
deflection is proportional to the applied pressure when calibrated.
Description of Bourdon tube Pressure Gauge:
The main parts of this instruments are as follows:
An elastic transducer, that is bourdon tube which is fixed and open at one end to receive the
pressure which is to be measured. The other end of the bourdon tube is free and closed. The
cross-section of the bourdon tube is elliptical. The bourdon tube is in a bent form to look like a
circular arc. To the free end of the bourdon tube is attached an adjustable link, which is intern
connected to a sector and pinion as shown in diagram. To the shaft of the pinion is connected a
pointer which sweeps over a pressure calibrated scale.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : To study the Bourdon tube.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Operation of Bourdon tube:
The pressure to be measured is connected to the fixed open end of the bourdon tube. The applied
pressure acts on the inner walls of the bourdon tube. Due to the applied pressure, the bourdon tube
tends to change in cross – section from elliptical to circular. This tends to straighten the bourdon
tube causing a displacement of the free end of the bourdon tube.
This displacement of the free closed end of the bourdon tube is proportional to the applied
pressure. As the free end of the bourdon tube is connected to a link – section – pinion arrangement,
the displacement is amplified and converted to a rotary motion of the pinion.
As the pinion rotates, it makes the pointer to assume a new position on a pressure calibrated scale
to indicate the applied pressure directly. As the pressure in the case containing the bourdon tube is
usually atmospheric, the pointer indicates gauge pressure.
Applications of Bourdon Tube pressure gauge:
They are used to measure medium to very high pressures.
Advantages of Bourdon tube pressure gauge
•
These Bourdon tube pressure gauges give accurate results.
•
Bourdon tube cost low.
•
Bourdon tubes are simple in construction.
•
They can be modified to give electrical outputs.
•
They are safe even for high pressure measurement.
•
Accuracy is high especially at high pressures.
Limitations of bourdon tube pressure gauge
•
They respond slowly to changes in pressure
•
They are subjected to hysteresis.
•
They are sensitive to shocks and vibrations.
•
Amplification is a must as the displacement of the free end of the bourdon tube is low.
•
It cannot be used for precision measurement.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Strain Gauge
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim: - Study of Strain Gauge
Theory
Strain Gauge :
If a metal conductor is stretched or compressed, its resistance changes on account of the fact that both
the length and diameter of the conductor change. There is also a change in the value of resistivity of
the conductor when it is strained and this property is called piezoresistive effect. This is the principle
of strain gauge. Strain gauge is a device the electrical resistance of which varies in proportion to the
amount of strain in the device. The most widely used gauge is the bonded metallic strain gauge.
A strain gauge of length L, area A, and diameter D when unstrained has resistance
R = (ρL)/ A
When a gauge is subjected to positive strain, its length increases while its area of
cross section decreases, resistance of gauge increases with positive strain
Strain definition :
Strain is the amount of deformation of a body due to an applied force. More
specifically, strain (ε) is defined as the fractional change in length, as shown below.
Strain can be positive (tensile) or negative (compressive). Although dimensionless, strain is sometimes
expressed in units such as in/in or mm/mm. In practice, the magnitude of measured strain is very small.
Therefore, strain is often expressed as
micro strain (µ-strain), which is ε x 10-6.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Strain Gauge
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Types of Strain gauges :
1. Unbonded metal strain gauges.
2. Bonded metal wire strain gauges.
3. Bonded metal foil strain gauges.
4. Vacuum deposited thin metal film strain gauges.
5. Sputter deposited thin film metal strain gauges
6. Bonded semiconductor strain gauges.
7. Diffused metal strain gauge
Bonded metallic (Foil type) strain gauges are commonly used due to their advantages over other strain
gauges thus it is discussed in detail below. The metallic strain gauge consists of a very fine wire or,
more commonly, metallic foil arranged in a grid pattern. The grid pattern maximizes the amount of
metallic wire or foil subject to strain in the parallel direction as shown below. The cross sectional area
of the grid is minimized to reduce the effect of Shear strain and Poisson Strain. The grid is bonded to a
thin backing, called the carrier, which is attached directly to the test specimen. Therefore, the strain
experienced by the test specimen is transferred directly to the strain gauge, which responds with a
linear change in electrical resistance. Strain gauges are available commercially with nominal resistance
values from 30 to 3000Ω, with 120, 350 and 1000Ω being the most common values
It is very important that the strain gauge be properly mounted on to the test specimen so that the strain
is accurately transferred from the test specimen, through the adhesive and strain gauge backing, to the
foil itself. A fundamental parameter of the strain gauge is its sensitivity to strain, expressed
quantitatively as the gauge factor (GF). Gauge factor is defined as the ratio of fractional change in
electrical resistance to the fractional change in length.
The Gauge Factor for metallic strain gauges is typically around 2.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Strain Gauge
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Signal conditioning stages for strain gauge :
Amplification :
Strain gauges typically provide small signal levels. It is therefore important to have accurate
instrumentation to amplify the signal before it is given to next stage i.e ADC, display etc.
Excitation :
Strain gauges require voltage excitation to generate a voltage representing strain. This voltage source
should be constant and at a level recommended by the strain gauge manufacturer.
Bridge Completion :
Strain gauges are offered in several different configurations: quarter-bridge, halfbridge, and full bridge.
For quarter and half-bridge strain gauges, instrumentation should provide bridge completion, adding
the necessary resistors to complete a Wheatstone bridge.
1. Full-bridge strain gauge : The entire Wheatstone bridge is provided with the strain gauge.
Instrumentation only needs to provide the excitation inputs.
2. Half-bridge strain gauge : Half of the Wheatstone bridge is provided with the strain gauge.
Instrumentation needs to provide two of the four resistors to complete the Wheatstone bridge. This is
known as half-bridge completion.
3. Quarter-bridge strain gauge : Quarter of the Wheatstone bridge is provided with the strain gauge.
Instrumentation needs to provide three of the four resistors to complete the Wheatstone bridge. This is
known as quarter-bridge completion.
Linearization/Strain Gauge Conversion :
While strain gauges are close to linear, they do stray from linear at large strains. In addition, it will
need some hardware or software to convert the voltage output of the strain gauge into a
strain measurement. The conversion formula depends on the type of strain gauge used. Half and
full-bridge strain gauges offer more accurate
conversion formulas.
Offset Nulling Circuitry :
A strain gauge application will have some position that will be identified as the rest
position (a reference position). The strain gauge should produce 0 volts at this
position. Offset nulling circuitry is used to produce 0V at rest position.
Conclusion:
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Linear variable
differential transformers (LVDT)
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim: - Study of Linear variable differential transformers (LVDT)
Theory
Linear variable differential transformers (LVDT) are used to measure displacement. LVDTs operate on the
principle of a transformer. As shown in figure 1, an LVDT consists of a coil assembly and a core. The coil
assembly is typically mounted to a stationary form, while the core is secured to the object whose position is
being measured. The coil assembly consists of three coils of wire wound on the hollow form. A core of
permeable material can slide freely through the center of the form.
The inner coil is the primary, which is excited by an AC source as shown. Magnetic flux produced by the
primary is coupled to the two secondary coils, inducing an AC voltage in each coil.
Figure 1
The main advantage of the LVDT transducer over other types of displacement transducer is the high degree
of robustness. Because there is no physical contact across the sensing element, there is no wear and tear in
the sensing element. Because the device relies on the coupling of magnetic flux, an LVDT can have infinite
resolution. Therefore the smallest fraction of movement can be detected by suitable signal conditioning
hardware, and the resolution of the transducer is solely determined by the resolution of the data acquisition
system. LVDT Measurement:
LVDT measures displacement by associating a specific signal value for any given position of the core. This
association of a signal value to a position occurs through electromagnetic coupling of an AC excitation
signal on the primary winding to the core and back to the secondary windings. The position of the core
determines how tightly the signal of the primary coil is coupled to each of the secondary coils. The two
secondary coils are series-opposed, which means wound in series but in opposite directions. This results in
the two signals on each secondary being 180 deg out of
phase. Therefore phase of the output signal determines direction and its amplitude, distance.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Linear variable
differential transformers (LVDT)
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All) DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Figure 2 depicts a cross-sectional view of an LVDT. The core causes the magnetic field generated by the
primary winding to be coupled to the secondary. When the core is centered perfectly between both
secondary and the primary, as shown, the voltage induced in each secondary is equal in amplitude and 180
deg out of phase. Thus the LVDT output (for the series-opposed connection shown in his case) is zero
because the voltages cancel each other.
Figure 2
Displacing the core to the left (figure 3) causes the first secondary to be more strongly coupled to the
primary than the second secondary. The resulting higher voltage of the first secondary in relation to the
second secondary causes an output voltage that is in-phase with the primary voltage.
Figure 3
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Linear variable
differential transformers (LVDT)
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Likewise, displacing the core to the right causes the second secondary to be more strongly coupled to the
primary than the first secondary as shown in figure below. The greater voltage of the second secondary
causes an output voltage to be out of phase with the primary voltage.
Figure 4
To summarize, "The LVDT closely models an ideal zero-order displacement sensor structure at low
frequency, where the output is a direct and linear function of the input. It is a variable-reluctance device,
where a primary center coil establishes a magnetic flux that is coupled through a center core (mobile
armature) to a symmetrically wound secondary coil on either side of the primary. Thus, by measurement of
the voltage amplitude and phase, one can determine the extent of the core motion and the direction, that is,
the displacement." Figure below shows the linearity of the device within a range of core displacement. Note
that the output is not linear as the core travels near the boundaries of its range. This is because less magnetic
flux is coupled to the core from the primary. However, because LVDTs have excellent repeatability,
nonlinearity near the boundaries of the range of the device can be predicted by a table or polynomial
curve-fitting function, thus extending the range of the device.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Linear variable
differential transformers (LVDT)
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Construction:
The physical construction of a typical LVDT consists of a movable core of magnetic material and three coils
comprising the static transformer. One of the three coils is the primary coil and the other two are secondary
coils.
Features and applications:
LVDTs have certain significant features and benefits, most of which derive from its fundamental physical
principles of operation or from the materials and techniques used in its construction.
1. Friction-Free Operation:
One of the most important features of an LVDT is its friction-free operation. In normal use, there is no
mechanical contact between the LVDT's core and coil assembly, so there is no rubbing, dragging or other
source of friction. This feature is particularly useful in materials testing, vibration displacement
measurements, and high resolution dimensional gauging systems.
2. Infinite Resolution:
Since an LVDT operates on electromagnetic coupling principles in a frictionfree structure, it can measure
infinitesimally small changes in core position. This infinite resolution capability is limited only by the noise
in an LVDT signal conditioner and the output display's resolution. These same factors also give an LVDT its
outstanding repeatability.
3. Unlimited Mechanical Life:
Because there is normally no contact between the LVDTs core and coil structure, no parts can rub together or
wear out. This means that an LVDT features unlimited mechanical life. This factor is especially important in
high reliability applications such as aircraft, satellites and space vehicles, and nuclear installations. It is also
highly desirable in. many industrial process control and factory automation systems.
4. Over travel Damage Resistant:
The internal bore of most LVDTs is open at both ends. In the event of unanticipated over travel, the core is
able to pass completely through the sensor coil assembly without causing damage. This invulnerability to
position input overload makes an LVDT the ideal sensor for applications like extensometers that are attached
to tensile test samples in destructive materials testing apparatus.
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Linear variable
differential transformers (LVDT)
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
5. Single Axis Sensitivity:
An LVDT responds to motion of the core along the coil's axis, but is generally insensitive to cross-axis
motion of the core or to its radial position. Thus, an LVDT can usually function without adverse effect in
applications involving misaligned or floating moving members, and in cases where the core doesn't travel in
a precisely straight line.
6. Separable Coil and Core:
Because the only interaction between an LVDT's core and coil is magnetic coupling, the coil assembly can be
isolated from the core by inserting a nonmagnetic tube between the core and the bore. By doing so, a
pressurized fluid can be contained within the tube, in which the core is free to move, while the coil assembly
is unpressurized. This feature is often utilized in LVDTs used for spool position feedback in hydraulic
proportional and/or servo valves.
7. Environmentally Robust:
The materials and construction techniques used in assembling an LVDT result in a rugged, durable sensor
that is robust to a variety of environmental conditions. Bonding of the windings is followed by epoxy
encapsulation into the case, resulting in superior moisture and humidity resistance, as well as the capability to
take substantial shock loads and high vibration levels in all axes. And the internal high-permeability magnetic
shield minimizes the effects of external AC
fields. Both the case and core are made of corrosion resistant metals, with the case also acting as a
supplemental magnetic shield. And for those applications where the sensor must withstand exposure to
flammable or corrosive vapors and liquids, or operate in pressurized fluid, the case and coil assembly can be
hermetically sealed using a variety of welding processes. Ordinary LVDTs can operate over a very wide
temperature range, but, if required, they can be produced to operate down to cryogenic temperatures, or,
using special materials, operate at the elevated temperatures and radiation levels found in many nuclear
reactors.
8. Null Point Repeatability:
The location of an LVDT's intrinsic null point is extremely stable and repeatable, even over its very wide
operating temperature range. This makes an LVDT perform well as a null position sensor in closed-loop
control systems and high performance servo balance instruments.
9. Fast Dynamic Response:
The absence of friction during ordinary operation permits an LVDT to respond very fast to changes in core
position. The dynamic response of an LVDT sensor itself is limited only by the inertial effects of the core's
slight mass. More often, the response of an LVDT sensing system is determined by characteristics of the
signal conditioner.
10. Absolute Output:
An LVDT is an absolute output device, as opposed to an incremental output device. This means that in the
event of loss of power, the position data being sent from the LVDT will not be lost. When the measuring
system is restarted, the LVDT's output value will be the same as it was before the power failure occurred.
Conclusion:
PREPARED BY : Prof. S.S.Chate
APPROVED BY: Dr.G.S.Sable
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Full wave rectifier.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Aim: To study Full wave Bridge Rectifier Circuit
Apparatus:
1. Analog board of AB09.
2. AC power supplies of 0-9Vrms from external source or ST2612 Analog Lab.
3. Oscilloscope.
4. 2 mm patch cords.
Circuit diagram :
Circuit used to study the Half wave Rectifier is shown in figure :
Theory:
Rectifier is an electronic device that converts alternating current into direct current. A rectifier
changes AC into DC by eliminating the negative half-cycles of the alternating voltage, so it
provides a one way path for electric current i.e. conduction takes place in one direction only. It is in
this way that a rectifier converts an alternating current into unidirectional current.
Rectifier can be classified into two categories:
1. Half-wave rectifier
2. Full-wave rectifier
Full Wave Rectifier :
The DC level obtained from a sinusoidal input can be improved to 100% using a process called full
wave rectification.
A full wave rectifier can be classified into two categories:
a. Center-Tapped full wave rectifier
b. Full-wave Bridge Network
Full Wave Bridge Network :
Bridge network requires four diodes for its operation. The circuit diagram is shown in figure.
During the period 0 to t/2 diodes D2 and D3 are conducting while diodes D1 and D4 are in off state,
so for the ideal diodes the load voltage Vo =Vi. For the negative portion of the input voltage diodes
D1 and D4 are conducting resulting in positive pulse across load resistor RL.
Vdc=.636Vm
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Full wave rectifier.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Advantages of Bridge Rectifier :
1. The need for center tapped transformer is eliminated.
2. The output is twice that of center-tap circuit for the same secondary voltage.
3. The PIV is one half that of the center-tap circuit.
Disadvantages of Bridge Rectifier :
1. It requires four diodes.
2. As during each half cycle of ac input diodes that conduct are in series, therefore the voltage drop
in the internal resistance of the rectifying unit will be twice as great as in the center circuit. This is
objectionable when secondary voltage is small.
Important parameters for rectifier circuits :
Peak inverse voltage :
The maximum reverse-bias potential that can be applied to a diode before entering the Zener region
is called peak inverse voltage or peak reverse voltage.
Half wave Rectifier PIV rating ≥ Vm
Center tap Full wave Rectifier PIV rating ≥ 2Vm
Full wave Bridge Rectifier PIV rating ≥ Vm
Rectification efficiency :
The ratio of DC output power to the AC power input in a rectifier is known as rectification
efficiency.
Efficiency of Half wave rectifier :
is diode resistance
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Full wave rectifier.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
Efficiency of Full wave rectifier (Center tap and Bridge Rectifiers) :
Ripple factor :
The ratio of r.m.s. value of AC component to the DC component in the rectifier output is known as
ripple factor. The smaller the ripple factor, the lesser the effective AC component and hence more
effective is the rectifier.
Mathematical analysis
Half wave rectification :
Putting values in eq.3 we get
Ripple Factor=1.21
For Full wave rectifier Ripple factor=0.48
Procedure :
Connect 0-9Vrms from ST2612 Analog Lab or from Analog Digital Lab Power Supply or from
any external source (transformer o/p) to sockets g and c of AB09 Board respectively using 2mm
patch cords.
1. Connect sockets b with d and h with f using 2mm patch cords to complete the bridge rectifier
circuit and also connect a patch cord between socket a and m/n.
2. Connect 2mm patch cord between sockets e and j. This will connect load resistance RL across
the output of Bridge rectifier (keep AC/DC push button switch of oscilloscope in AC position)
Maharashtra Institute Of Technology,
Aurangabad
LABORATORY MANUAL
Practical Experiment Instruction Sheet
EXPERIMENT TITLE : EXPERIMENT TITLE : Study of Full wave rectifier.
EXPERIMENT NO. : MIT(T)/ETC/Basic Electronics/Manual No.1
Class: FY(All)
DEPARTMENT: Electronics & Telecommunication Engineering
LABORATORY : Basic Electronics
Location
Part II
Page 3
3. Output DC voltage can be measured by pressing the AC/DC push button switch of the
oscilloscope or connecting a digital multimeter across sockets j and n i.e. across the load resistor
and carry out following calculations.
4. Now connect the 2mm patch cord between i and l socket. This will connect the filter capacitor
across the o/p of full wave bridge rectifier.
5. Observe the filtered output on oscilloscope.
Results :
1. Output voltage Vo =…………………………………..
2. Efficiency (using eq.1) = ………………………………