KELVINS DOUBLE BRIDGE

AIM: To measure the unknown resistance by using Kelvin double bridge.

APPARATUS REQUIRED:

1. Kelvin double bridge 2. Unknown resistance

3. Super sensitive galvanometer

4. Variable DC source with short circuit

5. Current limitation

THEORY

1. Set the zero of the built in galvanometer in the free position and the set

pointer in the center.

2. On the left side of bridge, there are two current terminals marked +C and C and two potential terminals +P and P. Four leads are provided, one pair is called current leads and the second is called potential leadsRY:

3. If the resistance to be measured in the form of two terminals resistance. The

leads from +C and +P are connected to one terminal and those from C and P are connected to another terminal of the unknown resistance. If the resistance to be measured this in the form of four terminel resistance then

leads from +C, +P,-C, -P should be connected to respective terminals of

unknown resistance taking proper care for polarity.

4. If the unknown resistive has been suitably connected choose the suitable

range multiplier depending upon the magnitude of the unknown resistance a

push button is provided which when depressed brings into circuit

simultaneous the battery and galvanometer by depressing the key

momentaries only and by adjusting the mail dial and slide wire.

5. If the resistance in the form of a wire or coil connect one end of the wire to

+C and to other end to +P and C to P with help of leads provided. The R of the wire between +C and C.

6. The zero of the slide wire should be checked off and on for doing so, the leads

from +C to +P and C to P are shorter together with help of any terminal resistance box etc. Keep the main Dail to zero position and use range of

X 10 and to get null point should be obtained with the main and slide wire both

reading zero.

7. Connect the main leads to 220 AC mains

MODEL CALCULATION:-

UN KNOWN RESISTANCE X= M (R+_ r)

At Normal

X1 = M(R+ r)

At Reversal

X2 = M(R- r)

Average unknown resistance X= {M(R+ r) + M(R- r)}/2

TABULAR FORM: Type Multiplier

factor

Resistance

M.R ()

Internal

resistance

r()

Unknown

resistance()

Normal

Reverse

PRECAUTIONS: 1. Avoid loose connections.

2. Readings are taken without parallax error

RESULT:

SCHEARING & ANDRESON S BRIDGE

AIM: To measure the values of unknown capacitance using schearing bridge.

APPARATUS REQUIRED:

1. Schearing Bridge.

2. Head phones.

3. Connecting wires

THEORY:

PROCEDURE: 1. Connect Ac supply of 1 kHz to the supply terminals.

2. Set the standard capacitor switch to 0.1 F position and set the decode

capacitor and dial Cs to any value say at 500PF. 3. Now set decode resistance dial RL with alternative adjustment, we can get the

minimum sound or no sound in the head phone.

4. The same experiment can be performed with anther value of standard

capacitor C2 C3.

5. Note down the value of R1 R2 C2 C3 and calculate the unknown capacitors &

dissipation factor

MODEL GRAPH:

MODEL CALCULATIONS:

C1 = C2 R4 / R3

C2 = R2 C2 / R1

Dissipation factor D1 = 2F C1 r

R = R1 Cs / C2

TABULAR FORM:

SR.NO. R1 R2 C1 C2 C3 D

PRECAUTIONS:

1. Avoid the loose connections.

2. Readings are taken without parallax error

RESULT:

AIM:

To find the self conductance of coil by Anderson bridge method

APPARATUS REQUIRED;

1. AC Galvanometer

2. DC supply

3. 4mm socket

THEORY:

PROCEDURE:

DC Balance:

1. Make the connections using dc supply and galvanometer.

2. Connect any one unknown inductance to unknown terminals.

3. Adjust the rheostat dial R to find out the null point in the galvanometer.

.4.Use the decade resistance dial S only for fine balance in the galvanometer and note R. AC Balance

1. Replace the dc supply with ac supply of frequency 1 kHz and

galvanometer by head phones.

2. Set the standard capacitor switches at position of 0.1F and adjust the variable resistance dial r to minimize the sound in the head phones 3. Note the values of the decade resistance dials r 4. The same experiment can be performed with another value of standard

Capacitance

5. Now calculate the unknown inductance (L) using the formulae

L= CR(Q+Zr)

MODEL CALUCULATIONS:

Unknown inductance L=CR(S+2r)

For, C=0.2

TABULAR FORM:

S.NO

C(F) V()

S()

R()

L(H)

PRECAUIONS

1. Take the readings without parallax error.

2. Loose connections should be avoided in the circuit.

RESULT

MEASUREMENT OF PARAMETERS OF CHOKE COIL

AIM:

To measure the parameters of given choke coil by using three voltmeter method.

APPARATUS:

S.NO

APPARATUS RANGE

TYPE

QUANTITY

1.

2.

3.

4.

5.

Voltmeter

Ammeter

Rheostat

Choke coil

Connecting

wires

( 0-300)V

(0-2)A

290/2.8A

PROCEDURE:

1. Connections are made as per the circuit diagram.

2. Observe the Vr , V and V3 for the given record these in observation table .

3. Change the load resistance R measure in observation table and record its value in the observation table.

4. Calculate the value of R and record in observation table.

5. Take another set of the observations of VR ,V , V3 calculate the power and

power factor and tabulate these in observation table.

6. Take at least 3 sets of observation for the different values of R and calculate

power, impedance resistance & inductance.

MODEL CALCULATIONS

Cos C = V2 - VR2 - VL2 / 2 VR VL RL = ZL Cos C XL = Z2 - RL2 L = XL / 2f Total power factor = VR + VL Cos C/V

TABULAR FORM:

S.NO V1

(Volts)

I

(Amps)

VR

(Volts)

VL

(Volts)

R1

(Ohms)

L

(H )

Power

factor

Cos

PRECAUTIONS: 1. Avoid the loose connections.

2. Readings are taken without parallax error.

RESULT

THREE AMMETER METHOD

AIM:

To measure the parameters of the given choke coil by using three

ammeter method.

APPARATUS:

S.NO

APPARATUS RANGE

TYPE

QUANTITY

1.

2.

3.

4.

5.

Voltmeter

Ammeter

Rheostat

Choke coil

Connecting

wires

( 0-300)V

(0-2)A

290/2.8A

PROCEDURE: 1. Make the connections are made as per the circuit diagram.

2. Measure the value of R and record the readings in the table . 3. Observe I1 , I2 and I3 for a given load, record these in the table .calculate the

power factor power given choke coil.

4. change the resistance R measure it and disconnecting it from the circuit .

5. Take the another set of the observation with the different values of

R and calculate the power & power factor in each case.

MODEL CALCULATIONS:

Cos C = I2 - IR2 - IL2 / 2 IR IL

ZL = V/ IL

RL = ZL Cos C

XL = Z2 - RL2

L = XL / 2f

Total power factor = IR + IL Cos C / I

S.NO V1

(Volts)

I

(Amps)

VR

(Volts)

VL

(Volts)

R1

(Ohms)

L

(H )

Power

factor

Cos

PRECAUTIONS: 1. Avoid the loose connections.

2. Readings are taken without parallax error.

RESULT

LVDT CALIBRATION

AIM: To measure the linear displacement by linear variable differential

transformer.

APPARATUS REQUIRED:

1. LVDT

2. Instrumentation tutor

3. Connecting wires

PROCEDURE: 1. Secondary terminals of LVDT are connected to instrumentation tutor kit

2. LVDT is energized by giving supply.

3. LVDT is adjusted to null position by adjusting zero adjust on trainer kit. This is observed on display of trainer.

4. LVDT is given the displacement Record the measured value of the

displacement on display actual displacement from LVDT scale.

5. Calculate the percentage error.

6. Repeat the same for different displacement.

MODEL CALICULATIONS: Micro meter actual reading =

Actual displacement of the core d1=

Indicating reading r1=

Error= d1- r1

% Error = {(d1- r1)/ d1}*100

TABULAR FORM:

Micrometer

actual reading

(d2)

Actual core

displacement

(d1)

Indicating

reading (r1)

Error

(d1- r1)

% Error =

{(d1- r1)/

d1}*100

PRECAUTIONS: 1. Readings are taken without parallax error.

2. Avoid loose and wrong connections.

RESULT

CALIBRATION OF WATTMETER BY PHONTUM LOADING

AIM:

To calibrate the LPF wattmeter by phantom loading.

S.NO

APPARATUS RANGE

TYPE

QUANTITY

1.

2.

3.

4.

Voltmeter

Ammeter

Wattmeter

Rheostat

(0-300)

(0-10A)

300v/5A

180/5A

MI

MI

LPF

Wire

wound

1

1

1

1

PROCEDURE: 1. The connections are made as per the circuit.

2. The current through the current coil of the wattmeter is varied with the help of

resistance in values steps.

3. The each step voltmeter, ammeter and wattmeter readings are noted.

4. The % error &% corrections are calculated

MODEL CALUCULATIONS:

V= I= W=

Standard reading Ws=VI

%error=[(W1-Ws)/Ws]100

%Correction=

S.NO

V (VOLTS)

I

(AMPS)

Wattmeter

reading

wwatts

Standard

reading

[Ws]

VI watts

%error

(W1-W2)

%Correction

PRECAUIONS: 1. Take the readings without parallax error.

2. Loose connections should be avoided in the circuit.

RESULT:

MESUREMENT OF STRAIN USING STRAIN GUAGE

AIM: To find % error in the reading can be calibrate by comparing particularly

practice values with the theoretical values.

APPARATUS REQUIRED:

1. Strain guage trainer board

2. Weights

3. Strain guage beam

PROCEDURE: 1. Connect the wires as per colour.

2. Switch on the apparatus.

3. Connect the apparatus to the beam.

4. Wait for 10 min. till it warm.

5. Adjust the digital reaction to zero units the knob provided.

6. Apply weight in step to 100gms.

7. For each weight note down digital display.

8. Calculate the theoretical values.

9. Observe the practical value.

10. Find out the difference b/w theoretical and practical values.

11. Difference gives an error.

MODEL CALICULATIONS: P=

S= (6PL)/ (BT2E)

Error= P-T

% Error= {(P-T)/ (T)}*100

L= Effective length of beam

B= Width of beam

T= thickness of beam

Y= Youngs modules

TABULAR FORM:

Weight (gm)

Practical

micro strain

(P)

Theoretical

micro strain

(T)

Error= P-T

% Error=

{(P-T)/(T)}*100

PRECAUTIONS:

1. Avoid loose connections.

2. Readings are taken without parallax error.

RESULT

CALIBRATION OF DYNAMOMETER TYPE POWER FACTOR

METER

AIM:

To calibrate the given dynamometer type power factor meter.

APPARATUS

S.NO

APPARATUS

RANGE

TYPE

QUANTITY

1.

2.

3.

4.

5.

Voltmeter

Ammeter

Wattmeter

Power factor

meter

Rheostat

( 0-300)V

(0-2.5)A

300V/5A

300V/5A

290/2.8A

PROCEDURE:

1. The connections are made as per the circuit diagram.

2. The inductive load is varied and the readings of wattmeter, voltmeter, and

ammeter are noted.

3. The above step is repeated for different power factors of the inductive load.

4. The capacitive load is connected and varied the readings of wattmeter,

voltmeter, ammeter are noted.

5. The above step is repeated for different power factors of the capacitive load.

MODEL CALCULATIONS:

Cos ' = W/VI

% Error = Cos - Cos ' / Cos '

TABULAR FORM

S.NO

I

(Amps)

V

(Volts)

W

(Watts)

P.F

Cos

Cos ' = W/VI

%

error

%

correction

PRECAUTIONS:

1. Avoid the loose connections.

2. Readings are taken without parallax error

RESULT

CROMPTON DC POTENTIOMETER

AIM:

To calculate the PMCC voltmeter & ammeter by using Compton

potentiometer.

APPARATUS REQUIRED

S.NO

APPARATUS

RANGE

TYPE

QUANTITY

1.

2.

3.

4.

5.

6.

Voltmeter

Ammeter

Rheostat

R.P.S

Voltmeter

ratio box

DC source

( 0-30)V

(0-2)A

290/2.8A (0-30)

PROCEDURE: 1. Connect the galvanometer standard cell & battery to their approximate

terminals on the potentiometer observing the current polarity of the

standard cell & battery.

2. Connect high resistance box in series with the galvanometer, introduce a

resistance of the order of 10k in the galvanometer circuit. 3. Note down temperature of standard cell and find out on it s voltage at that

particular temperature.

4. Set the potential dials to the exact voltage of the standard cell.

5. for the final balance galvanometer in series resistance should be decreased

zero .

6. Galvanometer should no direction with standard dise key pressed and zero

series resistance then the potentiometer has been standerise

MEASURING POTENTIALS: 1. Keeping the case polarities , connect the potential source to be measured to

the terminals on the potentiometer other terminals need to the disturbed.

2. Set the potential dial to the essential value of meter to be measure . If it is

unknown.

3. Find balance galvanometer series resistance should be decreased to zero .

4. Galvanometer should not dire action with test key pressed and zero series

Resistance

MEASURING A HIGH DIREACT VOLTAGE:

1. Connect the supply to be measured to the approximate terminals of the volt

ratio box i.e ve on terminals +ve to any of the input terminals depending up on the voltage supply.

2. Standardize the potentiometer and measure the unknown voltage.

MEASURING A HIGH DIREACT CURRENT: 1. Select a suitable potentiometer shunt depending on the range current

measurement .

2. Connect to the current terminals of the shunt .

3. connect to the terminals of the potentiometer.

4. Make sure the connections are usual.

5. Standardize the potentiometer and measure the unknown the potential

across the shunt terminals as usual.

MODAL CALCULATIONS:

Calibration of voltmeter:

Measured voltage Vm = V x M

% Error = Vm V/V Calibration of ammeter:

Im = V/s

% Error = Im I/I

TABULAR FORM:

Calibration of PMMC voltmeter:

S.NO

V(Volts)

Potential

reading(mv)

Measuring

voltage (Vm)

% Error =

{(Vm-V)/(V)}*100

Calibration of PMMC Ammeter:

S.NO

I(Amp)

Potential

reading(mv)

Measuring

current (Im)

% Error =

{(Im I)/(I)}*100

PRECAUTIONS:

1. Avoid loose connections.

2. Note down the readings without parallax error.

RESULT