Faculty of Engineering & Technology , Gurukula Kangri University , Haridwar

TACHOMETERSubmitted by:-

ASHWINI KUMARBranch:- Electrical

Class:-B.Tech

Roll no:- 11Roll no:- 11

FACULTY OF ENGINEERING& TECHNOLOGY,GURUKULA KANGRI VISHWAVIDYALAYA

HARIDWARFriday, September 06, 2013

ACKNOWLEDGEMENT

I express my sincere gratitude to ……………………. , Pro. & Head, Department of, faculty of Engineering & technology GuruKula kangri Vishwavidyalaya, for his cooperation and encouragement.

I would also like to thank my seminar guide …………….. , (lecture, Department of EE), for

I would also like to thank my seminar guide …………….. , (lecture, Department of EE), for their invaluable advice and wholehearted cooperation without which this seminar would not have seen the light of day.

Gracious gratitude to all the faculty of the Department of EE & friend for their valuable advice and encouragement.

Friday, September 06, 2013

CERTIFICATEThis is to certify that ASHWINI KUMAR of B.Tech 2nd

year Electrical Engineering student delivered a seminar report on Tachometer.

His Performance in this seminar was excellent / very good/good.good/good.

Guided By

Mr. Kuldeep sir Friday, September 06, 2013

CONTENTS1. Introduction

2. Working principle

3. Types of tachometer

4. Comparison between analog and digital tachometer

5. Classification of tachometer5. Classification of tachometer

6 Digital tachometer

7. Specification of tachometer

8. Block diagram of tachometer

9. Analog tachometer 10. How to choose a tachometer

11. Calibration of tachometerFriday, September 06, 2013

Tachometer, What’s That?

�Tachometer is used for measuring the

rotational speed of machine

�Can be used to measure speed of a

rotating shaft of machinerotating shaft of machine

�Can also be used to measure flow of liquid

by attaching a wheel with inclined vanes

�Can also be used to measure the speed of

car or watchFriday, September 06, 2013

Working Principle�Pules are fed to the tachometer at the

frequency to be measured. A scale factor is

applied to produce readings of desired

types (linear speed, flow rates etc.).types (linear speed, flow rates etc.).

�Tachometer works on two basic principles:-

a) Principle of the fixed time base tachometer

b) Principle of the reciprocal tachometer


Principle of the fixed time base

tachometer

�The tachometer totals the no. of pules receive during fixed period of time known as time base. At the end of this period a value for frequency measured is shown on the display.

� The time base can be set at the time of installation. It is calculated by:-

B =

where:- B = time base

Nt = no. of revolution per minutes

Nd = no. of pules per revolution

V = value appear on display

V x 60Nt x Nd


Principle of the reciprocal

tachometer

�This tachometer measure the interval between

n count pules and then perform the

calculation:-

f = 1

f =

where:- f = frequency

T = no. of intervals

1T


What Are the Different Types of

Tachometer?

�Tachometers can be classified on the basis of

data acquisition – contact or non contact

types

�They can also be classified on the basis of the �They can also be classified on the basis of the

measurement technique – time based or

frequency based technique of measurement

�They can also be classified as analog or digital

type


Comparison Between Analog and

Digital Tachometers

Analog tachometer

�Has a needle and

dial type of interface

�No provision for

Digital tachometer

�Has a LCD or LED

readout

�Memory is provided �No provision for

storage of readings

�Cannot compute

average, deviation,

etc

�Memory is provided

for storage

�Can perform

statistical functions

like averaging, etc


Classification Based on Data

Acquisition Technique

�Contact type – The wheel of the

tachometer needs to be brought into

contact with the rotating objectcontact with the rotating object

�Non Contact type – The

measurement can be made without

having to attach the tachometer to

the rotating object


DIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERSDIGITAL TACHOMETERS


Classification Based on Measurement

Technique

�Time Measurement – The

tachometer calculates speed by

measuring the time interval between measuring the time interval between

the incoming pulses

�Frequency Measurement – The

tachometer calculates speed by

measuring the frequency of the

incoming pulses Friday, September 06, 2013

Comparison Between Time and

Frequency Based Measurement

Time based

� The tachometer calculates speed by measuring the time interval between pulses

� More accurate for low speed

Frequency based

� The tachometer calculates speed by measuring the frequency of pulses

� More accurate for high speed measurement

� More accurate for low speed measurement

� Time to take a reading is dependent on the speed and increases with decrease in speed

� The resolution of the tachometer is independent of the speed of the measurement

measurement

� Time to take a reading is independent of speed of rotation

� The resolution of the tachometer depends on the speed of the rotating shaft


Typical Specifications of a Non Contact

Type Tachometer• Display 5 digits large LCD• Range: 2.5 - 99,999 RPM• Distance: 50 to 1,000 mm; 12 to 40 inches.• Resolution: 0.1 RPM<1000 RPM (2.5

to 9,999 RPM)1.0RPM >1000 RPM

• Measurement angle: at less than 120 • Measurement angle: at less than 120 degrees.

• Range selection: Auto• Laser Output Power: <1mW class II• Sampling Time: 1.0 seconds (over 60 RPM)• Memory: Last value, Max Value, Min. Value• Time base: Quartz crystal• Circuit: Exclusive one-chip LSI circuit• Battery: 4 X 1.5V AA• Weight: 300g/0.65lb• Size: 190 X 72 X 37 mm


Typical Specifications of a Contact Type

Tachometer• Display 5-digit LCD Display• Range selection Automatic range selection• Time Base 4MHz Quartz Crystal• Sampling Time 1 second (>60 rpm); >1

second (10 to 60 rpm)• Accuracy ± (0.1% of reading + 2 digits)• Photo Tachometer Distance 2 to 12” (5 to • Photo Tachometer Distance 2 to 12” (5 to

30cm)• Operating Temperature 32 to 122oF (0 to

50oC)• Operating Humidity 80% RH Max.• Power supply 9V Battery• Battery Life 40 hours (approx.)• Applicable standards EN 50081-1/1992 (EN

55022) EN 50082-1/1997 (EN 55024)• Dimensions 461700: 4.9 x 2.0 x 1.3” (124 x

51 x 33mm)• Weight 461700: 4.0 oz. (114g) Friday, September 06, 2013

Block Diagram of a Digital

Tachometer

Display

Microcontroller

Memory

Optical /

magnetic sensorSignal

conditioning

External

port (to

controller)

Block DiagramFriday, September 06, 2013

Optical Sensing

�It is used to generate pulses proportional to the

speed of the rotating shaft

�Can be achieved by the following ways:

– Attaching a disk, which has an alternate black – Attaching a disk, which has an alternate black

and white pattern, to the shaft and reading

the pulses by a IR module pointed towards it

– Using a slotted disk and a U shaped IR emitter

detector pair to generate waveforms


Magnetic Sensing

• Hall effect sensors – These make use

of the Hall effect to generate pulses

proportional to the speed of the proportional to the speed of the

shaft

• Passive magnetic sensors – These

make use of variable reluctance to

generate pulses


Signal Conditioning

• The output of the sensors may be

noisy

• The output may have to be amplified• The output may have to be amplified

• It has to be digitized. This is done by

Schmitt triggering so as to bring

voltage to TTL levels


Microcontroller

• Not essential, but is generally the norm to have a microcontroller

• Compute the speed

• Can store the readings• Can store the readings

• Can output values to a display unit

• Give out warning signal when speed reduces / increases beyond set margins

• Transfer data to external controller


Display Unit

• Used to output the values to the

operator

• Can be used to view the stored • Can be used to view the stored

values


ANALOG TACHOMETERANALOG TACHOMETER


Analog Tachometers

• These are generally the ones that

display the speed of your car

• The interface is needle and dial • The interface is needle and dial

arrangement


Analog Measurement

Techniques• Generally speed is converted to voltage

through the use of an external frequency to voltage converter

• The tachometer can also act as a generator • The tachometer can also act as a generator and produce a voltage that is proportional to the speed of the shaft

• This voltage is then displayed by an analog voltmeter


How To Choose a

Tachometer?• Accuracy

• Precision

• Range

• Acquisition Time• Acquisition Time

• Contact type / Non Contact type

• Portable / Fixed

• Digital / Analog

• Cost


Calibration

• Why calibrate?

– Wrong calibration = Wrong readings

– Calibration compensates for ageing, wear and tear

and other degrading effectsand other degrading effects

• How to calibrate?

– Calibration is done by comparing the reading from

tachometer to a standard speed

– Necessary changes are made so that the actual

reading matches the desired reading


THANK YOU☺

ASHWINI KUMARASHWINI KUMARASHWINI KUMARASHWINI KUMAR

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