m i lab.pdf

P.S.R ENGINEERING COLLEGE, SIVAKASI-626140.DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

YEAR: II SEMESTER: III

LAB MANUAL(2012 2013)

EE 2208MEASUREMENTS AND INSTRUMENTATION

LABORATORY

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERINGEE 2208 MEASUREMENTS AND INSTRUMENTATION LABORATORY

LIST OF EXPERIMENTS

Sl. No. EXPERIMENT NAME1. Study of DC Bridges (Wheatstone Bridge and Kelvins Double Bridge)2. Study of Schering Bridge3. Calibration of Single Phase Energy Meter4. Calibration of Current Transformer5. Measurement of Three Phase Power and Power factor6. Digital to Analog Converter7. Analog to Digital Converter8. Calibration of Three Phase Energy Meter9. Study of Pressure Transducer10. Study of Displacement transducer.11. Transient Response Of Series RC Circuit For DC Input12. Instrumentation Amplifier.

STAFF IN CHARGE H.O.D / EEE

1STUDY OF DC BRIDGESA. STUDY OF WHEATSTONE BRIDGE

AIM:To measure the unknown value of resistance of a resistor by using Wheatstone

bridge.REFERENCES:

1. A.K.Sawhney,A Course in Electrical & Electronics Measurements& Instrumentation, Dhanpat Rai and Co, 2004

2. J.B.Gupta, A Course in Electronic and Electrical Measurements, S.K.Kataria& sons, Delhi, 2003

APPARATUS REQUIRED:Sl.No. Name of the Equipment Range Type Quantity

1. Known resistances 100, 10DRB -2 (each)

12. Unknown resistances - - 13. Bread Board - - 14. Galvanometer 30-0-30 Analog 15. RPS (0-30V) Analog 16. Connecting Wires - - 1

FORMULA USED:Rx= (R1 * R3) / R2 ()

Where, R3 Variable Resistance ()R1& R2 Known Resistance ()Rx Unknown Resistance ()

THEORY:The DC bridges are used to measure the resistance while the ac bridges are used to

measure the impedances consisting capacitances and inductances. The two types of DC bridges

are 1.Wheatstone Bridge 2. Kelvin Double Bridge.

2CIRCUIT DIAGRAM:Wheatstone Bridge B

R1 =10 R2=100

A C

RX R3

D+ -

(0 30 V)RPS

TABULATION:Sl.No. Supply Voltage

(V)R3 () Rx = (R3 * R1)/ R2 ()

D

3The Wheatstone bridge consists of four resistance arms together with a source of e.m.f and a null

detector. The galvanometer is used as a null detector. The arms consisting of the resistances R1 &

R2 are called Ratio arms. The arm consisting of the resistor R4 is the unknown resistance value to

be measured. The battery is connected between A and C while galvanometer is connected

between B and D.

PROCEDURE:

1. From the available standard resistances, select a suitable value for the arms R1 & R2.

2. Select the suitable value for the resistance as R3.

3. Make the connections as per the circuit diagram.

4. Switch on the supply.

5. Adjust the value of DRB for null deflection in the galvanometer detector.

6. Increase the DC supply voltage continuously in steps and for each setting, obtain null

deflection.

DISCUSSION QUESTIONS:1. What is a DC Bridge?2. What are the types of DC bridges?3. What are the applications of Wheatstone bridge?

RESULT:Thus the measurement of unknown resistances using Wheatstone bridge was performed.

The values of unknown resistances are

5B. STUDY OF KELVINS DOUBLE BRIDGE

AIM:

To measure the value of unknown resistance using Kelvin bridge.

REFERENCES:1. A.K.Sawhney,A Course in Electrical & Electronics Measurements& Instrumentation, Dhanpat Rai and Co, 2004

2. J.B.Gupta, A Course in Electronic and Electrical Measurements,S.K.Kataria & sons, Delhi, 2003

APPARATUS REQUIRED:

Sl.No. Name of the Equipment Range Type Quantity

1. Known resistances 10, 100KDRB -2(each)

12. Unknown resistances - - 13. Bread Board - - 14. Galvanometer 30-0-30 Analog 15. RPS (0-30V) Analog 16. Connecting Wires - - Req.

FORMULA:

Rx= (P/Q) * S ()

Where, Q,P --- Upper bridge arm resistances()

S--- Variable Resistances ()

Rx--- Unknown Resistances ()

THEORY:

The bridge consists of another set of ratio arms hence called Double Bridge. The second set

of ratio arms in the resistances q & p with the help of these resistances the galvanometer is

connected to point 3. The galvanometer gives null indication when the potential of the terminal

6KELVINS DOUBLE BRIDGE:

P = 10 Q = 100

p = 10 q = 100RX DRB

S

RPS (0 30V)TABULATION:

Sl.No. P()Q()

S()

RX Actual()

RX = (P / Q) * S()

G

73 is same as the potential of the terminal 4. The important condition is that the ratio of the

resistance of ratio arms must be same the ratio of the resistances of the second ratio arms. When

both the contacts are switched to select the proper value of standard resistance the voltage drop

between the ratio arm connection points is changed but the total resistance around the battery

circuit is unchanged. With this arrangement, any contact resistance can be placed in series with

the relatively high resistance values of the ratio arms. Due to this, the effect of the contact

resistance becomes negligibly small. The ratio of R1 & R2 ie., R1 & R2 selected in such a way that

the larger part of the variable standard resistance is used and Rx is determined.

PROCEDURE:1. Connections are given as per the circuit diagram.2. Supply is switched ON.3. Galvanometer is connected in the deflector (mentioned) terminal and the zero

deflection value is obtained by varying the value of potentiometer.4. The value of Rx is calculated by using the formula.

DISCUSSION QUESTIONS:1.What is Kelvins double bridge?2. What are the advantages of bridge circuits?3. State the main differences between AC and DC bridges?

RESULT:

Thus the unknown value of resistance was measured by using Kelvins Double Bridge.

The unknown values of resistances are

9STUDY OF SCHERING BRIDGEAIM:

To measure the unknown value of capacitance of a capacitor by using ScheringBridge.REFERENCES:



APPARATUS REQUIRED:Sl.No. Name of the Equipment Range Type Quantity

1. Known capacitance 0.1 F - 12. Unknown capacitance - Box 13. Bread Board - - 14. Multimeter - Digital 15. AFO - Digital 16. Connecting Wires - - Required

FORMULA USED:Cx= (R1 * C2) / Rm ()

Where, Rm Multiple Resistances ()R1 Variable Resistance ()CxUnknown Capacitance (F)C2 Fixed Capacitance (F)

THEORY:Schering Bridge is one of the most widely used AC Bridge for measurement

of unknown capacitance, dielectric losses and power factors. It can be used for lowvoltages. The perfect capacitor Cx is to be measured. The Rx is series resistance C2 isstandard air capacitor having very stable value.R3 and R4 are non inductive resistancewhere C4 is variable capacitor.

Cx=(R4 / R3) *C2 ; Cx=(R4 / R3) * C2

10

CIRCUIT DIAGRAM:

C1RM

R1 1M 100K 10K 1K 100 1

To Detector

C20.1F CX

TABULATION:

SL.NO. R1()RM()

C2(F)CX(F)

1.2.3.4.5.

DISCUSSION QUESTIONS:1. What two conditions must be satisfied to make an AC bridge balance?2. What is Schering Bridge?3. What are the advantages of Schering Bridge?

11

PROCEDURE: Set the potentiometer to the initial position as mentioned above. Connect the unit to mains supply 220V AC through power cord. Switch ON the unit. The neon lamp will glow indicating that the unit is ready for

operation. Using patch cord feed the sine wave signal from the built-in oscillator to the bridge

circuit. Connect the unknown capacitance , whose value is to be determined , across

sockets marked Cx Connect a digital multimeter having a range of AC 0-200mV/0-2V across the

sockets marked TO DETECTOR and GROUND Using a patch cord , connect the topend of the bridge circuit to the multiplex

resistor (Rm) of value in the mid-range (like 1K ) Read the bridge output in the Digital multimeter. Change the multiplex resistor to successive higher or lower values, such that the

unbalanced output drops towards zero By selecting the appropriate value of Rm for minimum unbalance ,Vary the

resistance R1 to obtain the final balance point Correct balancing is obtained when the output drops almost to zero Disconnect all patch cords from the bridge circuit Using a digital multimeter , measure R1 Substitute the values of Rm, R1,and C2 in the formula and evaluate the unknown

capacitance

RESULT:Thus the unknown value of capacitance of a capacitor was measured using

Schering Bridge.The unknown capacitance value of the Capacitor is ..

13

CALIBRATION OF CURRENT TRANSFORMER

AIM:To study the working principle of current transformer and to calibrate the same.



APPRARATUS REQUIRED:Sl.No. Name of the Equipment Range Type Quantity

1. Ammeter (0 10A)(0 500mA)MIMI

11

2. Current transformer 200 / 5 A 13. Resistive load 3 kW Single phase 14. Voltmeter (0 300V) MI 15. Connecting wires Required

PRECAUTIONS: The secondary of the current transformer should not be open circuited while

primary winding is energized.FORMULA USED:

% ratio error = [(Nominal ratio Actual ratio) / Actual ratio] * 100Nominal ratio = Rated primary current of CT / Rated secondary current of CTActual ratio = Primary current (reading) of CT / Secondary current (reading) of CT

THEORY:The calibration is the procedure for determining the correct values of

measurand by comparing with the standard ones. The instrument with which comparison

14

CIRCUIT DIAGRAM:(0 10A) MI

10 A Current Transformer (200 / 5A)P

DPS (0 300V) MITS (0 500mA) MI

N10 A 1 Variac

(0 230/270V)TABULATION:

Sl.No. Primary CurrentIpy (A)Secondary Current

Isy (mA) Nominal Ratio Actual Ratio % error

MODEL GRAPH:

Primary Current Secondary Current

A

VLOAD

230 V1 ,50HzSupply

A ResistiveLoad 3 KW/ 230V

Secon

dary

Curre

nt

Nomi

nal R

atio

15

is made is called as a standard instrument. The instrument which is unknown and it issaid to be calibrated is called test instrument .Thus in calibration; test instrument iscompared with the standard instrument. There are two fundamental methodologies forobtaining the comparison between the test instrument and standard instrument. Thesemethodologies are Direct Comparison Indirect Comparison

PROCEDURE:1. Circuit connections are given as per the circuit diagram2. Supply is switched ON and by adjusting the Variac the rated voltage is set in the

voltmeter.3. By increasing the load in steps, the primary current and secondary current

ammeter readings are noted.

DISCUSSION QUESTIONS:1. What is calibration?2. What are the different calibration methodologies?3. What are the advantages of instrument transformers?4. Give the main differences between CT and PT.

RESULT:Thus the working principle of the Current Transformer was studied and

calibrated.

17

CALIBRATION OF SINGLE PHASE ENERGY METER

AIM:To calibrate the single phase Energy meter by direct loading.




1. Ammeter (0 10A) MI 12. Voltmeter (0 300V) MI 13. Energy meter 10A/230V Analog 14. Stop watch Analog 15. Connecting wires Required

FORMULA USED:Power= Voltage in Volts X Current in AmpsTrue Energy = Number of revolutions / Energy meter constantActual Energy = [(Power X Time taken for n revolutions) / (3600 X 1000)]% of Absolute error = (Actual Energy True Energy / True Energy) X 100

THEORY:The calibration is the procedure for determining the correct values of measurand by

comparing with the standard ones. The standard of device with which comparison ismade is called as a standard instrument. The standard instrument which is unknown andit is said to be calibrated is called test instrument .Thus in calibration; test instrument iscompared with the standard instrument. There are two fundamental methodologies forobtaining the comparison between the test instrument and standard instrument. Thesemethodologies are

18

CIRCUIT DIAGRAM:(0 10A) MI Energy Meter

10 AP C1 C2

D P1 P2PS (0 300V) MITS

N10 A 1 Variac

(0 230/270V)

TABULATION:

Sl.No. Voltage(V)Current(A)

Power(W)

Time(Sec)

No. ofrevolutions

ActualEnergy

TrueEnergy

%error

A

VLOAD

230 V1 ,50HzSupply

ResistiveLoad 3 KW/ 230V

19

Direct Comparison Indirect Comparison

The calibration offers a guarantee to the device or instrument that is operating withrequired accuracy under the stipulated environmental conditions. It creates the confidenceof using the properly calibrated instrument, in users mind. The periodic calibration ofinstrument is very much necessary.

The calibration procedure involves the steps like visual inspection for variousdefects, installations according to the specifications, zero adjustment, etc.PROCEDURE:

1. Circuit connections are given as per the circuit diagram2. Supply is switched ON by closing the DPSTS.3. By increasing the load in steps, the voltmeter, ammeter and wattmeter readings are

noted. Also the time taken for the energy meter disc to rotate for n revolutions isnoted down.

4. Using the formula the percentage error is calculated for each set of readings.

DISCUSSION QUESTIONS:1. What is creeping?2. Which torque is absent in energy meter? Why?3. Define energy meter constant.

RESULT:Thus the calibration of the single phase Energy meter was done and the Absolute

error was calculated.

20

CIRCUIT DIAGRAM: RESISTIVE LOAD

R 10 A(0 -10A) MI 600V, 10A, UPF

T M LP C V

415V R3 S (0 600V) MIY 10 A LOAD

50 HzSUPPLY

TS Y

B10 A

B C VM L

600V, 10A, UPF3 Variac

TABULATION:M.F.. M.F.

Sl.No.VL(V)

IL(A)

W1 W2 TotalPowerW1 + W2Watts

Phase angle

PowerfactorCos

ObservedReading

ActualReading

ObservedReading

ActualReading

M.F. Multiplication Factor

A

V

21

MEASUREMENT OF THREE PHASE POWER AND POWER FACTOR

AIM:To measure the 3 phase power using two single element wattmeter with 3 phase

resistive and inductive load.REFERENCES:



APPRARATUS REQUIRED:S.No. Name of the Equipment Range Type Quantity

1. Ammeter (0 10A) MI 12. Voltmeter (0 600V) MI 13. Wattmeter ( 150 / 300 / 600V)(5 / 10A)

Single elementUPF 1

4. Connecting wires Required

FORMULA USED:Phase angle, = tan- 1 3 [Higher reading lower reading]

[Higher reading + lower reading]Total Power = W1 + W2 (watts)Power factor = Cos

THEORY:Three phase power measurements can be done by the following methods,

i. By using three phase wattmeter.ii. By using 3-single element wattmeter i.e., three wattmeter method.iii. By using 2-single element wattmeter i.e., two wattmeter method.iv. By using 1-single element wattmeter i.e., one wattmeter method.

22

CIRCUIT DIAGRAM: INDUCTIVE LOAD

R 5 A(0 -5A) MI 600V, 5A, UPF

T M LP C V

415V A1C23 S (0 600V) MIY 5 A

50 HzSUPPLY B1A2

TS

5 A C1B2B C V

M L 3Phase600V, 5A, UPF Induction Motor

3 VariacTABULATION:

M.F.. M.F.

Sl.No.VL(V)

IL(A)

W1 W2 TotalPowerW1 + W2Watts

Phase angle

PowerfactorCos

ObservedReading

ActualReading

ObservedReading

ActualReading

M.F. Multiplication Factor

A

V

23

Among the above four methods, the most commonly used three phase powermeasurement techniques are, two wattmeter method and three wattmeter method.

PROCEDURE:1. Circuit connections are given as per the circuit diagram2. Supply is switched ON by closing the TPSTS.3. By adjusting the Variac rated voltage is set in the voltmeter.4. By switching ON the load (resistive / inductive) and increasing the load in steps,

the voltmeter, ammeter and wattmeter readings are noted.5. Using the formula the power factor is calculated.

DISCUSSION QUESTIONS:1. Define power factor.2. Explain why it is necessary to potential coil circuit purely resistive in wattmeters?3. Give the expression for 3phase power.4. What is LPF Wattmeter?

RESULT:Thus the 3 phase power was measured by using two single element wattmeters

and the power factor was calculated.

24

CIRCUIT DIAGRAM:(+5V)

MSBLSB

B0 B1 B2 B3 B4 B5 B6 B7

20 K 20 K 20 K 20 K 20 K 20 K 20 K 20 K

10 K 10 K 10 K 10 K 10 K 10 K 10 K 20 K

20 K47 K

10 K 72 47 K 7

6 23 6 Vo

34

TABULATION:DIGITAL INPUT ANALOG OUTPUT

(V)LSB MSBB7 B6 B5 B4 B3 B2 B1 B0 Practical Theoretical

25

DIGITAL TO ANALOG CONVERTER

AIM:To convert the given digital signal input to analog output.



APPRARATUS REQUIRED:S.No. Name of the Equipment Range Type Quantity

1. Digital to Analog Converter Kit - - 12. Patch cards - - Required

FORMULA USED:V0 = VR x RF / Rin{ Bo /2 + B1 /4 + B2 /8 + B3 /16 + B4 /32 + B5 /64 + B6 /128 + B7 /256 } Volts

PROCEDURE:1. Circuit connections are given as per the circuit diagram2. Supply is switched ON. By adjusting RPS V1 values are set and corresponding

output voltage V0 are noted down.3. Using the formula the gain is calculated.

DISCUSSION QUESTIONS:1. What are the different methods of D/A Conversion?2. What are LSB and MSB?3. Give the pin specifications of IC 741.

RESULT:Thus the performance of the D/A converter was studied.

27

ANALOG TO DIGITAL CONVERTER

AIM:To convert the given analog signal input to digital output.



APPARARATUS REQUIRED:S.No. Name of the Equipment Range Type Quantity

1. Analog to Digital Converter Kit - - 12. Patch cards - - Required

PROCEDURE:1. Circuit connections are given as per the circuit diagram.2. Supply is switched ON. For different values of analog input the corresponding

digital output values are noted down.3. The digital output values are tabulated.

DISCUSSION QUESTIONS:1. What are the different methods of A/D conversion?2. What is IC 7408?3. What is a clock signal?

28

TABULATION:

ANALOG INPUT (V)DIGITAL OUTPUT

MSB LSBB6 B5 B4 B3 B2 B1 B0

ANALOG VOLTAGE (V) INCREMENT CALCULATION

29

RESULT:Thus the performance of the instrumentation amplifier is studied and gain is

calculated.

30

CIRCUIT DIAGRAM:

31

CALIBRATION OF 3 PHASE ENERGY METER

AIM:To calibrate the 3 phase Energy meter by direct loading.




1. Ammeter (0 10A) MI 12. Voltmeter (0 600V) MI 13. Energy meter 3 14. Stop watch Analog 15. Connecting wires Required

FORMULA USED:Power= Wattmeter reading x Multiplication Factor(M.F)True Energy = Number of revolutions / Energy meter constantActual Energy = [(Power X Time taken for n revolutions) / (3600 X 1000)]% of Absolute error = (Actual Energy True Energy / True Energy) X 100

THEORY:Energy is the total power delivered and consumed over a time interval by

an electrical system.Energy=Power * Time

Electrical energy is expressed asW= VIt KwhV is expressed in volts,I is expressed in ampere and t is in seconds

32

TABULATION:

Multiplication Factor:.. Energy meter constant=

Sl.No. Voltage(V)Current(A)

WattmeterReading Time(Sec)

Number ofrevolutions

ActualEnergy

TrueEnergy

%error

Observed Actual

MODEL GRAPH:

%Error

Current

33

Unit for energy is joules or watt second. If the unit of time is taken as hour, energy is thenexpressed in watt hours, for larger units: energy may be expressed in kilo Watt HourPROCEDURE:

1. Circuit connections are given as per the circuit diagram2. TPSTS is closed and the load is applied gradually.3. Voltmeter, Ammeter and wattmeter readings and time taken for energy meter disc

to rotate n revolutions are noted.4. Percentage error is calculated for various load currents.

RESULT:Thus the calibration of the 3 Energy meter was done and the Absolute error was

calculated.

34

CIRCUIT DIAGRAM:

7 (+Vcc)2

6

34 (-Vcc)

Differential Amplifier Mircro Controller Output(Op-Amp) (Calibration) (LED Display)

+-

Strain GaugeTABULATION:Increasing Pressure

Sl.NO. APPLIED PRESSURE (Kg / Cm2) Output Voltage (mV)

Decreasing Pressure

Sl.NO. APPLIED PRESSURE (Kg / Cm2) Output Voltage (mV)

MODEL GRAPH: Vo (mV)

Decreasing Pressure Increasing pressure (Kg/ Cm2)(Kg/ Cm2)

Pressure

DisplayMicro

ControllerRAM EPROM

35

STUDY OF PRESSURE TRANSDUCERAIM:

To study the performance characteristics of Pressure Transducer.REFERENCES:



APPRATUS REQUIRED:Sl.No. Name of the Equipment Range Type Quantity

1. Pressure Transducer kit withFoot pump - - 1

THEORY:Pressure is the basically a physical parameter is defined as the force acting per

unit area measured at a given point or over a surface. Most pressure measuring devicesuse plastic members for sensing pressure at primary stage. These elastic members convertthe pressure into mechanical displacement which is later converted into electrical formusing a secondary transducer. The principle of working of these devices can be explainedas, the fluid or gas whose pressure is measured is made to press the pressure sensitiveelement and since the element is a elastic member it deflects causing a mechanicaldisplacement. The displacement is proportional to the pressure applied. Thedisplacement is then measured with a help of electrical transducer is proportional to thedisplacement and hence to the applied input pressure. The commonly used pressuresensitive devices are

Diaphrams Capsule Bourdon tubes Bellows

37

PROCEDURE:1. 230 V AC Main Supply is switched ON.2. By pressuring the pump, Pressure into the air cylinder is increased.3. The pressure and output voltage in the front panel of the trainer kit is noted.4. The pressure from the air cylinder is decreased in steps and the values of

pressure and voltage are tabulated.DISCUSSION QUESTIONS:

1. How the transducers are classified?2. Give the factors to be considered in selecting a transducer?3. What is an active transducer?4. What is a passive transducer?

RESULT:Thus the characteristics of Pressure Transducer were studied and the readings are

tabulated.

38

CIRCUIT DIAGRAM:A.C. Input

Primary of the transformer

Displacement

Secondary of the transformerEs1 Es2

VOTABULATION:Positive Displacement

Sl.No. MSR VSC TR = MSR +VSCx error Sensor Output (mV) Sensor Displacement (mm)

Negative Displacement

Sl.No. MSR VSC TR = MSR +VSCx error Sensor Output (mV) Sensor Displacement (mm)

MODEL GRAPH: Sensor Output (mV)

Negative Displacement Positive Displacement

Displacement (mm)

CORE

39

SYUDY OF DISPLACEMENT TRANSDUCERAIM:

To study and determine the performance characteristics of LVDT.REFERENCES:



APPRATUS REQUIRED:Sl.No. Name of the Equipment Range Type Quantity

2. LVDT kit - - 1

THEORY:The most widely used inductive transducer to translate the linear motion into electrical

signals is the linear variable differential transformer(LVDT).LVDT is a differential transformerconsisting of a single primary winding P and two secondary windings S1 and S2 wound over ahollow bobbin of non-magnetic and insulating material. The secondary windings S1 and S2 haveequal number of turns and are identically placed on either side of the primary winding. Amovable soft iron core is placed inside the transformer. The displacement to be measured isapplied to the soft iron core. In order to overcome the problem of eddy current losses in the core,nickel-iron alloy is used as core material and is slotted longitudinally.

Primary winding is connected to an AC source of voltage varying from 5 to 25V and offrequency ranging from 50Hz to 20kHz.Since the primary winding is excited by an alternatingcurrent source, it produces an alternating magnetic field which in turn induces alternatingvoltages. The output voltages of secondary winding S1 and ES1 and that of secondary winding S2is ES2.Inorder to convert the output voltage from S1 and S2 into a single voltage signal, the twosecondaries S1 and S2 are connected in series opposition as shown in figure. Therefore the outputvoltage of the transducer is the difference of the two voltages.

Differential output voltage E0=Es1-Es2

41

When the core is at its normal (NULL) position, the flux linking with both he secondarywindings are equal and hence equal emfs are induced in them. Thus at null position Es1=Es2.Sincethe output voltage of the transducer is the difference of the two voltages, the output voltage E0 iszero at null position. Now if the core is moved to the left of the NULL position, more flux linkswith winding S1 and Less wit winding S2.Hence output voltage Es1,of the secondary windingS1,is more than Es2,the output voltage of secondary winding S2,The magnitude of output voltageis,thus,E0=Es1-Es2 and the output voltage is in phase with the primary voltage. Similarly, if thecore is moved to the right of the null position,the flux linking with winding S2 becomes largerthan that linking with winding S1.Hence output voltage Es2 of the secondary winding is morethan Es1,the output voltage of the secondary winding S1.The magnitude of output voltage is thus,E0=Es2-Es1 and is 180 out of phase with the primary voltage. Thus the LVDT output voltage is afunction of the core position. The amount of voltage change in either secondary winding isproportional to the amount of movement of core. Hence, we have an indication of amount oflinear motion. By noting which output voltage is increasing or decreasing, we can determine thedirection of motion .Any physical displacement of the core causes the voltage of one secondarywinding to increase while simultaneously reducing the voltage in the order secondary winding.The amount of output voltage may be measured to determine the displacementPROCEDURE:1. Circuit connection is given as per the circuit diagram.2. The core is slowly moved and the displacement value and output voltage is noteddown.DISCUSSION QUESTIONS:1. What is a transducer?2. Mention some advantages of LVDT.3. List out the disadvantages of LVDT.4. Mention the applications of LVDT.

RESULT:Thus the characteristic of displacement Transducer was studied and the graph was

drawn.

42

CIRCUIT DIAGRAM:

(0-25mA)MC10K + -

(0-30V)MC+

RPS (0-30V) +DPSTS C

4700 F-

TABULATION:

Sl.No. CHARGING DISCHARGINGV(volts) T(sec) V(volts) T(sec)

A

V

43

TRANSIENT RESPONSE OF SERIES RC CIRCUIT FOR DC INPUT

AIM:To obtain transient response of RC circuit for DC input.




1. Resistors 10 K - 12. Capacitor 4700F - 13. RPS (0 30V) Analog 14. Ammeter (0-25mA) MC 15. Voltmeter (0-30V) MC 16. Bread Board - - 17. Stop watch - - 18. DPSTS - - 19. Connecting Wires - - Required

THEORY:In series RC circuit shown in figure, the switch S is in open state initially. There is

no charge on the capacitor and no voltage across it. At the instant t=0, switch S is closed.Immediately after closing the switch, the capacitor acts as a short circuit path, so currentat the time of switching is high. The voltage across the capacitor is zero at t=0 as thecapacitor acts as a short circuit, the current is maximum and is given by

I=V/R amperes.This current is maximum at t=0+which is called charging current. As the capacitor

starts charging, the voltage across capacitor Vc starts decreasing. After some time, when

44

MODEL GRAPH:

Capacitor charging capacitor Discharging

45

the capacitor charges to V volts, it achieves steady state. In steady state, it acts as an opencircuit, so the current will be zero finally.

Transient current, i= [V/R] X [et / RC]So at time t=0, i=V/R is maximum and in steady state it becomes zero.PROCEDURE:

1. Circuit connections are given as per the circuit diagram2. Supply is switched ON and capacitor is charges to its rated voltage in steps with a

time interval.3. The corresponding voltmeter readings and time interval are noted down.4. By discharging the capacitor from its rated voltage, in same steps the voltmeter

readings and time intervals are noted down.5. Graphs are plotted for charging and discharging of capacitor separately.

DISCUSSION QUESTIONS:1. What is transient?2. What is the time constant for RC series circuit?3. Define transient time?

RESULT:Thus the transient response of series RC circuit for DC input was obtained and the

graph was plotted.

46

CIRCUIT DIAGRAM:+ VCC

2 7 7 56 K6

3+ 12V 4 7

- VCC 12 K 26

3.9 KVo

1 K 1 K 12 K 3 4

0.4 K 56 K1 K 1 K

3.9 K7

26

34

TABULATION:

Sl. No.Input Voltage

(mV) Output Voltage(Vo)Gain Ad = Vo /Vin

Gain in dB = 20 log(Ad)V1 V2

47

INSTRUMENTATION AMPLIFIER

AIM:To construct and study the performance of instrumentation amplifier and to obtain

the gain.REFERENCES:




1. Op amplifier IC 741 3

2. Resistors1 K, 3.9 K,0.4 K, 12 K,

56 K- Each 2

3. RPS (0 30V) - 14. Bread Board - - 15. Connecting Wires - - Required

FORMULA USED:V0 = { (V1 V2) x R2 / Rf [1 + (2R1 / Rg)] } VoltsAd = (V0 / [V1 V2])

Theory:Physical quantities like temperature, humidity. Light intensity, water flow etc., are

usually measured with the help of transducers. The output of transducer has to beamplified, so that it can be drive the display system of control system. This function isperformed by an instrumentation amplifier. The important features of an instrumentationamplifier are

49

High input impedance. High gain accuracy High CMRR High gain stability with low temperature coefficient Low output impedance

PROCEDURE:1. Circuit connections are given as per the circuit diagram2. Supply is switched ON. By adjusting RPS V1 values are set and corresponding

output voltage V0 are noted down.3. Using the formula the gain is calculated.

DISCUSSION QUESTIONS:1. What is an instrumentation amplifier?2. List the important characteristics of operational amplifier.3. What are the applications of instrumentation amplifier?4. What is CMRR?

RESULT:Thus the performance of the instrumentation amplifier was studied and gain was

calculated.

m i lab.pdf

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