ics manual

8/17/2019 Ics Manual

1/28

STUDY AND CALIBRATION OF LVDT TRANSDUCER FOR

DISPLACEMENT MEASUREMENT.

AIM:

To determine the displacement of an object by using linear variable differential transformer

transducer, to compare it with a micrometer displacement and to establish accuracy of the

instrument.

APPARATUS:

1. LVDT transducer.

2. Micrometer.

3. Displacement sensor connecting rod.

4. Displacement indicator.

5. Multimeter.

6. Screw driver.

THEORY:

Displacement indicators & sensors (LVDTs) form a precise set up to measure linear

displacements to a better degree of accuracy than any mechanical measuring system. An added

advantage of this electronic type of measurement is its speed and ease of reading the value.

The displacement sensor comprises of a linear variable differential transformer coil and a

core which moves inside the coil according the displacement being measured.

The primary coil of LVDT is excited with a signal at a carrier frequency of 4KHz.the two

secondary coils, coupled inductively to the primary through the core are connected in signal

opposition in fashion, so that when the core is exactly at the center of the coil, the signal outputof the sensor is zero. When the core moves in one direction, the signal amplitude increases and is

in phase with the carrier and vice versa. Thus the sensor output is a true representation of the

amplitude and direction of displacement.

This model has provision to accept one LVDT sensor at a time. The displacement as

measured by the sensor at a time. The displacement as measured by the sensor is indicated on a


2/28

31/2 digit display. The displacement of the sensor is directly indicated mm. output proportional

to the display is also made available to the user on the real panel of the indicator. This output

can be connected to an oscilloscope for monitoring or to an XY or strip chart recorder for

recording purposes.

OSBSERVATIONS:

S.no Micrometer

readings

Corresponding

readings

L.V.D.T

readings

Voltage(V) Error micrometer LVDT displacement


3/28


4/28

PROCEDURE:

1. First of all take micrometer with range of 0-25 mm.

2. The transducer is placed in the micrometer groove and we ensure that there is no air gap

between core and micrometer.

3. Set the displacement indicator to „ZERO‟ by using a screw driver.

4. A small displacement say,2mm is given of LVDT core by micrometer now the readings

at the LVDT indicator is taken by using multi meter (0-10V) output voltages readings to

be taken.

5. When AC current is supplied to primary coil an alternating magnetic field is generated in

the circuit.

6. The magnetic field is disturbed by armature which is connected to moving body, a

voltage is developed in the two secondary coils.

7. Above procedure is repeated till the micrometer reads 20mm displacement at each step

the simultaneously readings of LVDT indicator and out put voltage readings are taken.

8. The entire out put voltage generated by the circuit equal to algebraic sum of individual

voltages developed by each secondary coil

E ckt= ES1-ES2.

9.

When the position of soft iron core exactly at center level then both ES1&ES2. Are same

Eckt= 0 .This position is called Null position.

10. When the position of soft iron core moves left side then ES1>ES2

11. When the position of soft iron core moves right side then ES1


5/28

PRECAUTIONS:

1. LVDT core and micrometer are mounted on instant fixture with curve and ensure that the

core and micro meter spindle lies in the same axis.

2.

Readings on the micrometer are noted with out parallax error.

RESULT: Hence, displacement is measured by using LVDT transducer and the average value

of error has been found to be studied.


6/28

STUDY AND USE OF A SEISMIC PICKUP FOR THE MEASUREMENT

OF VIBRATION AMPLITUDE OF AN ENGINE BED

AT VARIOUS LOADS.

AIM:

To study the use of piezoelectric accelerometer for the measurement of vibration parameters of

an engine bed at various points.

APPARATUS:

1. Vibration indicator.

2. Piezoelectric acceleration and its connecting wire and socket.

3. An external filter.

THEORY:

The study and measurement of vibration in any structure or machine is of paramount

importance for the following reasons:

1. Undesirable vibration is a waste of energy and causes wear & subsequent break-down

resulting in high maintenance costs.

2. The noise produced due to vibrating bodies or structures cause human fatigue resulting in

reduced efficiency.

3. Undamped vibrations transmitted to structures might excite vibrations at natural

frequencies and cause permanent damage.

The Accelerometer Model is a piezoelectric vibration sensor. When the piezoelectric element in

the sensor is strained by an external force displaced electric charges accumulate on opposing

surfaces forming a charge proportional to the force. This electric charge when applied to a very

high impedance amplifier produces a voltage signal proportional o the acceleration to which the piezoelectric element is subjected to. With this unique configuration vibrating frequencies of

near D.C up to 3000Hz can be very easily measured.

Buffer amplifiers, integrators and equalizers built in the Vibration Indicator help to measure

Vibration displacement, velocity and acceleration just by operating a rotary switch. Both Ac &


7/28

Dc recorder outputs are calibrated, buffered and brought to the recorder terminals facilitating

easy recording.

PROCEDURE:

1. Mount the vibration sensor rigidly on the vibrating body as shown in the figure. All the

detail given must be followed to obtain accurate results. In this case the highest frequency

of operator is reduced to 1000 Hz.

2. Clamp the cables to the vibrating body as shown in figure. This is essential to avoid cable

chip and sub vibration damage to the cable.

3.

Keep the vibration indicator suitable place and connect the power cord Before connecting

mains power to the indicator.After verification connect one end of mains cable supplied

,to the socket on the rare panel and other end to power source.

4. Inter connect the accelerometer and vibration indicator using the cable provided with

acceleration.


8/28

5. Keep‟IN/OUT‟ switch on the rare panel in position „OUT‟.

6. Select the parameter of interest on the function switch.

7. To start with select range.

8. Switch on the instrument and wait for 1minute for the capacitors to get charged.

9. Now the indicator is ready for making vibration measurement .

10. Select range A if reading is below 20 when measuring acceleration or velocity and 200

while measuring displacement.

11. Select range B for vibration levels between 20 & 200 for acceleration and velocity

,between 200 & 2000 µm for displacement.

12. Select range C for vibration levels beyond 200 for acceleration and velocity ,beyond 2000

µm for displacement.

13.

In order to analyze the vibrating motion an external active filter can be connected to

indicator and the procedure to be adopted as follows.

a. Mount the vibration sensor rigidly on the vibrating body as shown in the figure. All the

detail given must be followed to obtain accurate results

b. Clamp the cables to the vibrating body as shown in figure. This is essential to avoid cable

chip and sub vibration damage to the cable.

c. Keep the vibration indicator and active filter in the suitable position and connect the

power cord to the vibration indicator.

d. Keep the external filter ‟IN/OUT‟ switch on vibration indicator in position „IN‟

e. Select the function to be measured by switching “ACCEL/VEL/DISP” switch on

vibration indicator in the required position.

f. Keep the range switch on vibration indicator in position „C‟.

g. Switch „ON‟ the vibration indicator and wait for one minute for capacitors for get

charged.

h. Now procedural steps 11,12,13 will be followed for choosing appropriate ranges.

i.

The readings indicated are RMS values for acceleration and velocity peak to peak for

displacement and the units indicated by the LED adjacent to display window.

j. Select 23% band width on the band width selector.

k. Slowly tune the fine frequency dial for the maximum indication on the panel meter.


9/28

CALCULATION:

The vibration amplitude of engine bed

Trail 1:

Trail 2:

Trail 3:

Trail 4:

Trail 5:

Vibration amplitude = average of 5 trails.

RESULT:

The vibration amplitude of engine bed is: ---------- m/sec2.


10/28

STUDY AND CALIBRATION OF PHOTO AND MAGNETIC SPEED

PICKUPS FOR THE MEASUREMENT OF SPEED.

AIM:

To study and calibrate the speed by using magnetic and photo pickups.

APPARATUS:

1. Sensor for tacho pickups & photo pickup.

2. Two channel speed indicator(2 No.s)

3. One see clock generation circuit.

4. Input signal conditioning pre amplification.

THEORY:

TACHOMETER is designed to measure the speeds of rotating shafts, gears, turbines etc. the

sensor employed to sense the speed is of the variable reluctance type. This sensor picks up tacho

pulses from any rotating ferrous object, such as a gear, the number of such pulses being equal to

the number of times, the flux lines emanating from the sensor is cut by the alternate presence of

gap and teeth of the gear. The sensor is mounted in close proximity to the rotating body to ensure

sufficiently large voltage output for accurate indication of speed in RPM.


11/28


12/28

PROCEDURE:

1. Before connecting power to the indicator verify the power source available matches with

the requirements of indicator as maintained on the rear panel. After verification ,connect

one end of mains cable supplied to the socket on the rear panel and the other end to the

power source.

2. Connect the tacho sensor cable to input socket on the rear panel.

3. Switch on the indicator.

4. Mount the tachosensor and optical sensor in close proximity to the rotating shaft whose

speed is to be measured .The distance between the sensor force and the test tool should

not be more than 1.5 cm

5. The tachometer sensor and the photo sensor display speed of the rotating shaft directly in

RPM.

6. The motor speed can be controlled in the range 0-2000 rpm using knob provides on the

control panel.

OBSERVATIONS;

S.No Photo pickup(rpm) Magnetic pickup(rpm) Voltage(voltage)


13/28

PRECAUTIONS

1. The optical sensor and the tachosensor are mounted in close approximately to the

gearwheel.

2.

Always start the motor with zero speed and operate the knob slowly.

RESULTS

The speed of a given tooth gear is measured by using magnetic and photo pickups and the

speed is -------RPM.


14/28

CALIBRATION OF RESISTANCE TEMPERATURE DETECTOR

FOR TEMPERATURE MEASUREMENT.

AIM:

To calibrate and measure the temperature using Resistance Temperature detector.

APPARATUS:

Super dry heater oven with fan motor digital temperature indicator.

-Cr/Al ( K type)[Cr-chromel,Al-alumel]

-Fe-K(J type)

-PT-100(RTD)

THEORY:

When an electric conductor is subjected to a temperature change the resistance of the

conductor changes and this change in resistance of conductor becomes measure of change in

temperature when calibrated. The resistance of electric conductor increases with an increase in

temperature and vice versa.

The Super Dry Heat Oven, consists of an insulated enclosure having internal dimension

of 300mm D X 300mm H, with full size door. The oven is provided with mechanical convectioncirculating fan fitted with F. HP Motor, 1 KW Air Heaters (2 Nos. of 500 W) are located in the

air-duct of the oven. The air circulation system consists of a suction of hot air from the working

space, from the air-duct on the sides to maintain uniform temperature throughout the oven.

Temperature of the oven is indicated and controlled by Electronic Digital Temperature

Indicator Controller. Provision for setting and controlling the required temperature between

ambient to 2500C. The controller is provided with Press to set button and temperature is set by

adjusting Multitum Potentiometer which progressively increase temperature and can be set to

desired temperature to cut off the heaters at set temperature.


15/28

PROCEDURE:

1. In this experiment we are using copper as conductor than it requires three constants.

2. Adjust the required temperature carefully.

3. While conducting the experiment don‟t open the door.

4. Set the temperature of the control to the required temp say,2500C,switch on the

heater.

5.

A suitable bridge circuit is connected to two terminals to facilitate the measurementof resistance change in resistance element.

6. In operation when resistance element is subjected to medium where temperature is to

be measured.the resistance of the element gets changed.

7. The controllers cutoff the heater at the set temperature.


16/28

8. For every 200C temperature change of the controller the instantaneous temperature

reading of the three RTDs are noted down starting with 500C.

OBSERVATIONS:

S.No Standard

instrument readingTest meter reading Error in

0C

Ingrease Decrease PT-100 C R( C) J( C) PT-

1000C

R( C) J( C)

PRECAUTIONS:

1. Adjust the required temperature care fully.

2. While conducting the experiment do not open the door.

3. The readings of RTD should be taken instantaneously.

RESULT:

The calibration of temperature is done by using 3 RTDs.


17/28

CALIBRATION OF STRAIN GAUGE FOR

TEMPERATURE MEASUREMENT

AIM;

To measure the temperature y using strain gauge.

APPARATUS:

1. Heater and container

2. Thermometer

3. Digital panel meter.

PROCEDURE;

1. Switch on the panel.

2. Place the glass thermometer on the heat source.

3. Note down the temperature as actual reading

4. Place the strain gauge sensor tip on the heat source.

5. Note down the readings as indicated readings.

6. Calculate the error percentage and repeat the above.

OBSERVATIONS:

S.No Actual temperature ( C) Indicated temperature( C) Error percentage.


18/28

PRECAUTIONS;

1. Do not touch the main switch while control panel switch is on.

2. Avoid keeping it near to any magnetic material.

RESULT:

Temperature is measured by using the strain gauge.


19/28

STROBE SCOPE

AIM:

To measure the angular velocity of rotating member by using strobe scope.

APPARATUS

1. Strobe scope

2. Rotating member.

THEORY:

The stroboscope utilizes the phenomenon of vision when an object is vined intermittently. Thehuman sense of vision is so slow to react to light hat it is unable to separate two different light

impulses reaching the eye with in a very short period of time (less than 0.1 sec.)

There are two types of stroboscopes

1. Mechanical disk type stroboscope

2. Flash light stroboscope

Mechanical disk type stroboscope:

A mechanical disk type stroboscope consists of a whirling disk, stationary mark and rotationdisk. The whirling disk is attached to shaft whose speed is to be measured.

When the openings in the rotating disk and stationary mass coincide the observer catch fleeting

glimpses of the whirling disk. If the rotating disk is made to rotate with a period slightly less than

or greater than the period of whirling disk forward or backward creeping of the whirling disk can

be seen when the speed of rotating disk synchronized with the motion of the whirling disk. The

marking on the whirling disk appears to be motion less at the condition and can calculate the

speed of rotating shaft.

Speed of shaft = (disk speed) X (no of openings in the disk) / no of images

Flash Light Stroboscope:

It is modern type stroboscope which utilizes a controllable intense flashing light source instead

of a whirling disk. In this type neon gas discharge lamp uses a flashing light source. The flashing

ray is controlled by variable frequency electric oscillator. When the light flashes on to a rotating


20/28

disk and flashing ray is adjusted so that the rotating member appeared stationary. The frequency

of light flashes of the oscillator becomes equal to the frequency of the rotating member. At this

condition the frequency of light flashes indicates the speed of the rotating member.

PROCEDURE

1. Set a mark on the object, whose angular speed is to be measured.

2. Switch on the strobe scope by using the off- on switch and direct the flashing light on the

rotating object.

3. The flashing frequency can be varied and set by the operates by using cores fine adjusting

knob.

4. The frequency of the flashing is adjusted with the help of cores fine knob until target

aperies motion less or stationary.

5. Under this condition the speed of rotation of rotary member is equal to flashing frequency

of stroboscope.

fr= frequency of rotation of object

ff=frequency at flashing.

At synchronization fr=ff.

6. The scale of stroboscope is directly calibration in rpm which gives the speed at object in

term of rpm.

7. Checking should be done whether the reading is correct or not by changing the frequency

to have synchronize and not have multiple of speed.


21/28

PRECAUTIONS

1. Approximate estimation of speed is necessary other using it will give synchronize at

integral multiple of speed.

2. Do not use the instrument continuously more than 30 min. It advisable to give a break of

5 min.

3. Each time after use of instrument remove wire from mains.

RESULT

The angular speed of rotating member is measured by using stroboscope.

1.

The speed of the rotating wheel is = ---------- rpm.

2. The angular speed of the rotating wheel is = ------------- rad/sec.


22/28

STRAIN GAUGE

AIM:

To study the resistance strain gauge for force measurement.

APPARATUS:

1. Strain gauge and weight.

2. Weighting pan connecting cable.

3. Multi meter.

4.

Strain gauge indicator.

THEORY:

Stress and strain can be measured in many ways. Piezoelectric transducers use the fact

that, in piezoelectric materials, electric charge is separated when the materials is strained.

Strain gauges can be related directly to stress through the elastic modulus. Other typical

measurements are force, torque and pressure.

1. If the relationship between applied force and strain can e determined for a given

structure, then the strain gauges can be used to measure the force.

2. If the relationship between applied torque and strain can e determined for a given

structure, then the strain gauges can be used to measure the torque.

3. If the relationship between applied pressure and strain can e determined for a given

structure, then the strain gauges can be used to measure the pressure

THEORETICAL BACKGROUND:

For resister of uniform cross section A,of length L and and of resistivity ρ

R=ρL/A


23/28

if we take the differential of the reletion for resistance, we obatain

dR/R=dρ/ρ+dL/L-dA/A

But A= (π/4)*d2

But circle cross sectional conductor.

Log A = log (π/4) + 2log D

Differentiate on both sides

dA/A = 2 dD/D

dD/D= lateral strain

dR/R = dS/S+dL/L+2γdL/L

but dL/L= ∑a

the gauge factor F is defined by

F= (dR/R)/∑a

Comparing equation we get F= 1+2ν+(1/∑a)dS/s

Strain of a member ∑a= 1/P(dR/R)

The bridge is balanced under unstrained condition

When the gauge is strained the resistance R, example by an amount dR then

R=R1+dR

Vab= [R1+dR/R1+R2+dR] Vs

Vad= [R3/R3+R4] Vs= Vs/2

The change in output voltage is

Vo= Vab-Vad =[(R+dR/2R+2dR)-0.5] Vs


24/28

= dR/4R+2dR Vs

Use of white stone bridge to measure change in resistance balanced condition

Quarter Bridge:

Only one strain gauge is used and there three elements of bridge are fixed the resistors let

it be presented that the measuring instrument has infinite impedance and therefore no current low

through it

I1= in current flowing in the limbs AB & BC

= Vs/R1+R2

Vab= voltage drop in limb AB I1R1= R1/R1+R2 Vs

Vad= voltage in limb AD I2R2= R3/R3+R4 Vs

Initially all the fore limbs constructing the bridge have resistant of equal magnitude

R1=R2=R3=R4=R

Vab= Vad= Vs/2

Vab=Vad=0

Half bridge:

When no strain is applied Vab=Vad=Vs/2

The terminal B & D are at same rotational the bridge is taken balanced and output votage

Vo=0

When load in applied 40 the beam the resistance of the gauge R. increase due to tensile

load while the resistance R2 decrease due to equal compressive strain.

R1=R1+dR

R =R2-dR


25/28

Vab= [R1/(R1+R2)] Vs= [R1+dR/( R1+dR+ R2-dR)]= R+dR/R1+R2 Vs

= (R1+dR/2R) Vs

Vab= R3/R3=R4 Vs =Vs/2

Becomes dVo=Vs/2*dR/R = (Vs/2)Ft

Which is twice the output wheat stone bridge using one gauge only?

Full bridge:

When no strain is applied Vab= Vad= Vs/2

The terminals of B&D one at same potential the bridge is men balanced and output voltage Vo=0

when load is applied to the beam the resistance R1&R4 increase due to tensile load when

strained the resistace of various gauge are

R1=R4=R+dR(tensile)

R2=R3=R-dR(compression

Potential of terminal B is Vad= R3/R3+R4 Vs

Vo=Vab=Vad= R1=dR/2R Vs- R-dR/2R Vs

=Vs dR/R

dVo= Vs dR/R

which is 4 times the output of wheat stone bridge using one gauge only


26/28

PROCEDURE:

1. Switch on the instrument and allow a few minutes for warm up.

2. Keep the select switch in to set position the display reads the set gauge factor value

without the decimal point i.e. a gauge factor 2.005 is displayed hear the gauge factor 2in

set.

3. The gauge factor if the instrument is 2.00 is set by signal adjusting multi time potential

meter using screw driver.

4. Before making any measurement the strain gauge bridge is balanced under no strain

conditions now the pan is hinged to the cantilever beam as shown in figure. Now

selection switches on the front panel of the indicator to be in to measure position.

5. By keeping the cores ‟0„switch in zero position adjust fine zero control with a screw

driver fill the display reading 0000.

6. For unbalanced zero may not be possible then put the force zero switch +0, +1 through

+4+0-1 “+hro “ -4 depending on direction and amount of unbalance by zero.

a. Full bridge (all 4arms active)

1. Select arm select arm switch 4 on both strain gauge and strain indicator.

2. The wire connection per strain indicator are

port color

A yellow

B green

C red

D black


27/28

b. Half bridge (2 arms active0

1. Select arm select arm switch 2 on both strain gauge strain indicator.


port color

A black

B -

C brown

D orange

c. Quarter bridge

1. Select arm select arm switch on both strain gauge strain indicator.


port color

A white

B -

C blue

D black


28/28

PRECAUTIONS:

1. It ensure that should not be distributed.

2. Before staring experiment instrument ensure that appropriate arm selection switch and

wiring.

Result:

From calibration curve in load vs voltage, voltage vs micro strain, micro strain force can be

calculated.

ics manual

Documents