A REPORT

ON

ELECTRONIC & INSTRUMENTATION

BY

Name of the Student DHIRAJ KUMAR

AT

HINDUSTAN COCA-COLA BEVERAGES PVT. LTD.PATLIPUTRA, PATNA (BIHAR)

AARUPADAI VEEDU INSTITUTE OF TECHNOLOGYCHENNAI

DECEMBER-2010

i

A REPORT

ON

ELECTRONICS & INSTRUMENTATION

BY

Name of the ID. No. Discipline Student

DHIRAJ KUMAR 348074013 B.E(Hons.)EIE GAURI SHANKAR KUMAR 348074030 B.E(Hons.)EIE

Prepared in partial fulfillment of the Project

AT

HINDUSTAN COCA-COLA BEVERAGES PVT. LTD. PATLIPUTRA, PATNA (BIHAR)

HINDUSTAN COCA COLA BEVERAGES PVT. LTD.

PATNA

ii

Duration: 23 days Date of start : 24-12-2010

Date of submission: 15th January 2011 Title of project : ELECTRONICS & INSTRUMENTATION CONTROL

Name Discipline of Student : DHIRAJ KUMAR

Name and designation ofthe expert : Mr. Umesh Kr. Tiwary, Production Executive

Project areas : Electronic and Instrumentation

Abstract : Electronic & Instrumentation deals with a detailed study of the various electronic instruments which includes their principle of operation, construction details, advantageous features and some technical data. A special project on Auto Air control system based on the study is also presented in this report.

Signature of student Signature of the Expert

Date: Date

iii

ACKNOWLEDGEMENT

Before commencing with my project report, I would like to thank a few

people I am very much grateful. First of all I would like to thank Mr.Manish

Kumar (H.R.Manager, HCCBPL) and Mr. PRABHAT VERMA (Plant-

Manager, Hindustan Coca-Cola Beverages Pvt. Ltd.).

I would like to thank Mr.Debojit Sharma (Sr. Production Executive, HCCBPL

and Chief Coordinator of this training programme ) for having given me this

project work.

I would like to offer my never ending thanks to Mr. Umesh Tiwari (Sr.

Production Executive, HCCBPL) and Mr. Soumitra Paul (Production

Executive ,HCCBPL) who are my instructors for this project. Without their

efforts and help teaching me the series of operations to carry out this project I

wouldn’t have been able to accomplish it this much.

Last but not the least I would like to thank Mrs. L.Chitra ( Faculty, Aarupadai

Veedu Institute of Technology) for his sincere efforts and support through out

the practice programme.

iv

SYNOPSIS

TITLE PAGE NO.

INTRODUCTION 1

ELECTRONIC INSTRUMENTS 1 TEMPERATURE CONTROLLERS 2 PROXIMITY SWITCHES 3 LIMIT SWITCHES

4 TIMERS 5 UV DISINFECTION UNIT

SPECIAL PROJECT

v

A.INTRODUCTION

A.1 ABOUT COKE :

Coca cola, the very uttering of the name brings a dousing effect is the world ‘s

leading manufacturer of soft drinks. It was invented by John Pemberton in the year 1886.

It is the world’s most diverse soft drink company with its ingress in 200 countries, 215

nationalities and communicating in 126 languages. Coke entered India in 1952. Coke and

thums up were the main products during that period. Fanta and sprite were introduced in

1960 . Coke completed 100 years in 1986 when diet coke entered the markets.

Coke re-entered India in 1993. This plant HCCBPL, Patliputra was initially a

thums up unit in 1980 and coke took over later. This plant in the present time produces

fanta, coke , thums up & sprite. Maaza is not produced in this plant since it is the only

coke product which contains fruit and so it is produced in a separate plant.

A.2 BASIC PROCESS INVOLVED :

Any bottling industry comprises of these processes. Crates with empty bottles

are placed on conveyor. Bottles are removed from crates by the uncasing machine. Crates

are then sent to crate washer for water wash. Bottles separated from crates are sent to pre

inspection for removal of straws and other foreign items. The bottles are sent to bottle

washer where rinsing and soaking is done. Then before filling a final pre inspection is

done. The bottling machine’s capacity is 600 bottles per minute with 50 filling valves and

15 crowning heads. A casing machine finally cases these filled bottles.

A.3 INTRODUCTION TO INSTRUMENTATION AND CONTROL :

Electronic & instrumentation is a major branch of study for the electronic and

instrumentation engineers to learn the controls of various electronic instruments. To

know about an instrument in its depth is more important than to use it like a lay man.

This report also projects a special project on Auto Air control system based on the study

of all the instruments.

1

B.1 MAIN INCOMING SINGLE LINE

DIAGRAM

2

B.2 DB BLOCK DIAGRAM

3

B.2 DB BLOCK DIAGRAM(cont..)

4

B.3 EXPLANATION OF LAYOUT

B.3.1 MAIN DISTRIBUTION:

The Bihar State Electricity Board(BSEB) supplies 11KV supply to HCCBPL

through a CT(Current Transformer) placed just outside the plant. This supply is then

led into a secure energy meter room placed adjacent to it. The supply is then passed

through underground cables protected with sand for preventing moisture to a step down

transformer. This steps down 11KV to 400V. The stepped down supply is taken into an

ACB(Air Circuit Breaker).The purpose of ACB is that in case of puncture in the cables

the transformer has to be prevented from breakdown so this tripping device immediately

trips. If its just let without any measure the transformer has to be replaced and it requires

a high ransom for replacement. This is then fed into the MAIN DB which is divided into

four –MCCB1,MCCB2,Chilling Plant(old),Chilling Plant(new).The power supply to

these is from the BSEB. In case of power cut supply is given from Diesel

Generator(DG) set placed inside the premises which provides

380KVA(old),380KVA(new),125KVA for the above mentioned four. Supply from main

DB is fed into a power factor bank which comprises of 8 capacitors and supply to it has

to be given only from BSEB supply and not DG set.

B.3.2 SUB DB DISTRIBUTION:

Power from MAIN DB is divided into two broad sections – section1 and 2

each comprising of sub DBs.

5

B.3.2.1 SECTION1 :

It comprises of DB1(200A), DB2(200A), DB4(400A) and two

capacitors(25KVAR and 20KVAR).The ones in brackets are the incoming supply of the

DBs. DB1 supplies power to uncaser, empty case conveyor, bottle washer ,concentrate

room, post inspection conveyor and air compressor. The ratings of each of them is shown

in the layout. These rating nothing but the supply required for each. DB2 supplies power

to pressure less combiner, pre inspection conveyor (uncaser to bottle washer), paramix,

caser+ case washer. The power needed for each varies depending on the requirement.

The use of all the equipments are beyond the scope for electrical engineers. The work of

electrical engineer is to know how power is distributed and what is used to distribute the

power. DB4 supplies power to soft water panel , boilers ,WTP ,raw water reservoir

SECTION 2 :

It comprises of DB6(200A), DB8(300A) ,DB9(500A) and a

capacitor(25KVAR). DB6 provides power for lighting sugar room , Air Handling Unit

and other units present beside it. It consists of 4 pole MCBs the working of which will be

explained in detail. DB8 distributes power to liquid CO2 storage tank, raw water tank ,

full godown lighting and street lights. Basically incoming power is supplied to a main

switch and then its fed into bus bar which comprises of R,Y,B,N(Red, Yellow, Blue,

Black).The bus bar distributes power to the various components listed under each DBs.

Depending on the number of components the engineer can use as many bus bars. DB9

supplies power to ETP, ETP lighting, fire hydrant, borewell, bio-solids, HCl. The layout

also contains power distribution from ETP. ETP distribution comprises of air blower,

effluent pumps, lime, DAP, urea, effluent transmission pumps and sledge pumps. Thus

the work of an electrical engineer will be more efficient if the layout is known to him

properly before learning their controls.

6

C.1. MCCB

C.1.1 INTRODUCTION:

MCCB refers to MOULDED CASE CIRCUIT BREAKERS. The ever

increasing consumption of electrical loads in domestic, commercial as well as industrial

applications has necessitated the usage of higher rating protection devices. The Moulded

Case Circuit Breakers (MCCBs) render flexibility up to 100A and 125A load

requirements used in switch boards, lighting and power panel control boards.

C.1.2 PRINCIPLE:

MCCBs make use of the “blow apart” contact principle. Derived from the

basic laws of physics, this principle is based on the electromagnetic repulsion of

adjacent conductors transporting current in opposite direction. In these circuit breakers

contacts with carry current are arranged so as to create opposing magnetic fields. The

contact arms, one stationary and one movable are positioned close to one another. As the

fault current rises, magnetic repulsion forces the contacts to part. This forced separation

immediately establishes an arc. The arc acts as a major source of current impedance,

restricting fault energy to lower levels for fast extinguishing in the arc chamber.

The short circuit pivot design allows the moveable contacts to separate

completely from the stationary one without restrictions, even before the mechanism

unlatches to trip the MCCB. The higher the fault current, the faster the contacts part.

By generating dynamic impedance of the arc, the (I2t and Ip let through energy is greatly

limited, therefore protecting the down stream distribution system as well as extending the

life of the MCCB.

7

C.1.3 CONSTRUCTION:

Load line distribution boards are made of special grade CRCA sheet steel

manufactured with the latest technology using CNC punch and brake presses to attain

high degree of perfection. They are painted with polyester and polyester resin based

powder paints to ensure scratch resistance. The current carrying parts are made of

electrolytic grade copper and are over rated to carry high currents, keeping temperature

rise and distribution losses very low. The MCCB is a thermo magnetic trip free unit

with a positive contact indication designed for compactness and versatility.

C.1.4 FEATURES:

C.1.4.1 MINIMUM DOWNTIME:

Downtime is reduced and fuse replacement is eliminated. In case of overload

or short circuit, the breaker trips stopping current flow. After normal conditions are

restored, the breaker can be closed again.

C.1.4.2.TRIP FREE MECHANISM:

An integral part of the quick-make quick break mechanism that is independent

of the handle toggle. This prevents the ability of the breaker contacts from being held

closed should an overload or short circuit occur.

C.1.4.3.COMMON TRIP:

MCCBs eliminate single phasing. When an overload or short circuit occurs in

any phase, a common trip mechanism disconnects all the three phases of a multi-pole

circuit breaker.

C.1.4.4.SPACE SAVING:

MCCBs are space saving which is a major factor to equipment users. By

offering high interruption ratings in small compact frames, the savings to users can be

substantial.

8

C.1.4.5.MOULDED CASE:

Circuit breaker housing is made of high compact, high dielectric strength

polymer material.

C.1.4.6.POSITIVE OPERATION:

The ON and OFF status is indicated by the position of the operating handle.

An intermediate position indicates that the breaker is in the tripped position.

C.1.4.7.QUICK-MAKE QUICK BREAK MECHANISM:

This type of mechanism minimizes arcing during operation as well as

preventing the contacts from being teased into the “ON” position.

C.1.4.8.FRONT ADJUSTABLE MAGNETIC TRIP:

Adjustable buttons are provided on the 250A frame to set the instantaneous

trip settings in event of a short circuit. Any current surge above the trip setting produces a

magnetic field which instantly actuates the trip mechanism and opens the MCCB.

C.1.4.9.THERMAL TRIP:

This provides protection against the sustained overloads. A bi-metallic

element in each conductor path reacts time-wise in inverse proportion to the current. If a

circuit is overloaded, heat resulting from excessive current flow causes the bi-metal to

bend, actuating the rip mechanism to open the breaker.

C.1.4.11.ARC CHUTES:

Arc chutes are designed to confine, divide and extinguish an arc each time the

breaker contacts interrupt a short circuit. The arc chute therefore must dissipate the arcs

that are caused when the circuit breaker interrupts the current flow. It contains a stack of

U-shaped steel plates held together by insulating material. The steel plates divide the arc

and cools the gases generated by the arc.

9

C.1.5.FIELD FITTABLE ACCESSORIES:

Application flexibility of MCCBs is enhanced by a convenient accessory line

comprising under voltage release, shunt trip, auxiliary switch, alarm contact, front drive.

C.1.5.1.AUXILLARY SWITCH:

A combination of 2(1 NO + 1NC contacts) are available for annunciation,

remote indication of the ON/OFF position of MCCB and for the use in the control

circuit.

C.1.5.2.SHUNT TRIP:

A range of shunt releases suitable for AC/DC supply are available for remote

tripping of the circuit. For operating the shunt trip, one contact of the auxiliary switch

has to be used.

C.1.6.ADVANTAGES:

High current rating( up to 125A)

Close overload and short circuit protection

High breaking capacity(up to 25KA)

(In most high rise buildings, the transformer is either located in the

basement or within the premises. The prospective short circuit current is

generally higher than 10KA. A protective device with lower breaking

capacity cannot protect against such faults thereby exposing the entire

system. However, by the use of MCCBs the system can be easily

protected)

Accessories available for annunciation and remote tripping.

C.1.7 TECHNICAL DATA OF A MCCB:

LOAD SUPPLY : 440V,50HZ

CURRENT RATING : 80A,100A,125A

SC TRIPPING CURRENT : 800A (for 80A)

: 1200A(for 100/125A)

SC BREAKING CAPACITY : 10KA/16KA/25KA

INSULATION VOLTAGE : 660V

SPECIFICATION : IS: model number

10

C.2. MCB

C.2.1.INTRODUCTION:

MCB refers to MINIATURE CIRCUIT BREAKERS. In the residential,

commercial sectors, final electrical distribution needs are continuously evolving.

Improved operational safety, continuity of service, greater convenience and operating

cost have assumed tremendous significance.

C.2.2 PRINCIPLE:

MCB is a high fault capacity, thermal/magnetic, current limiting, trip free

switching device with fast magnetic tripping. Two kinds of operations are involved:

Thermal operation with inverse time-current characteristic for

overload protection

‘Hammer trip’ assisted magnetic operation for short circuit

protection.

Thermal operation is achieved with a bimetallic strip, which deflects when

heated by any over currents flowing through it. In doing so, releases the latch mechanism

and causes the contacts to open. Inverse time current characteristics result, i.e. greater

the overload current, shorter the time required to operate the MCB.

When short circuit fault occurs, the rising current energizes the solenoid,

operating the plunger to strike the trip lever causing immediate release of the latch

mechanism. Rapidity of the magnetic solenoid operation causes instantaneous opening of

the contacts

.

C.2.3.CONSTRUCTION:

The outgoing MCBs can be mounted on the DIN channels provided n the

horizontal Distribution Boards. In case of vertical DBs the MCBs are terminated by

screwing on the bus bar. Copper bus bars per phase according to the number of

outgoings and load requirement are provided along with Earth bars, Brass Neutral bars

and special brass terminals to ensure perfect connections and safety.

11

C.2.4. FEATURES:

C.2.4.1. CURRENT LIMITING DESIGN:

During short circuit current breaking of 10KA, the MCB does not allow such high

current to pass through it.Current reversal produces repelling magnetic field and

introduces high resistance in circuit to limit the current to values between 2.5 to 3KA.

This reduces the let through energy (I2t) and opening time, and results in low arcing and

effective arc-quenching. Forced magnetic opening due to reversal of current between

fixed and the movable contact further accelerates in quicker opening time.

C.2.4.2.HAMMER TRIP:

It is considered that just the use of current limiting design may not suffice the

requirement of quick breaking, mainly due to inertia of the latch mechanism and inter

connected sequence of operations. A hammer directly connected to plunger strikes the

moving contact with a force proportional to current peak, and current peak, and

thereby forcibly separates the contacts much before the latch mechanism operates. The

opening time of the MCB is reduces less than 1ms.This helps in reducing the let through

energy heating during short circuit, and ensures positive opening of he contacts.

Possibility of contact weld is completely eliminated.

C.2.4.3. ARC CHUTE:

The arc produced on separation of contacts is rapidly moved, under the

influence of a magnetic field and arc guide, into the arc chute stack, where it is broken

down into partial arcs. These partial arcs require a considerably higher voltage than that

required to maintain a single arc. The arc is therefore cooled and extinguished very

quickly to ensure longer life of the MCBs.

C.2.4.4.DUAL TERMINATION:

Box terminals are provided for both incoming and outgoing. The

accommodation of bus bar as well as cable termination facility. Also the terminals are

fully shrouded thus eliminating any possibilities of operator coming in contact

inadvertently with any of the live parts.

12

C.2.4.5.SILVER GRAPHITE CONTACTS:

Contact bounce when making high short circuit currents, results in contact

welding in pure silver or ordinary silver alloy contacts. It is a non melting sintered

material with very high melting point. The possibility of arc erosion is eliminated since

the fiber like graphite grain alignment is perpendicular to the movement of the arc. Hence

the contact life increases.

C.2.4.6.HOUSING:

The body is made of flame retardant high strength thermo set material which

has a high melting point, low water absorption at saturation, high dielectric strength, high

deflection temperature under load and low co-efficient of linear thermal expansion.

C.2.4.7.WATCH CASE MECHANISM:

All moving parts are completely encased in a sheet metal frame. This makes

their movement independent of the upper or lower plastic cover, just as all movements in

a wrist watch are independent of the base and glass cover in which they are enclosed.

Since plastic tends to change its shape and accuracy under continuous load and

temperature stresses, the sheet metal frame enables the MCB to have a consistent

tripping and protects the case from deforming.

C.2.4.8.TRIP FREE MECHANISM:

The tripping of the MCB is independent of the position of the knob i.e. while

operating knob may be held in the ON position the MCB will still open in the event of a

fault.

C.2.4.9.VIBRATION:

MCBs can withstand vibration limits upto 3 ‘g’ continuous duty .For practical

applications like usage in locomotives and electric trains MCBs are very suitable

13

C.2.5.ADVANTAGES:

High short circuit making and breaking capacity.

Current limiting plus ‘hammer trip’ for low let through energy and

maximum safety

Protection to downstream switch gear applications.

No faults due to ageing.

Compact dimension and modular construction.

Offers fuse less distribution system.

Protection to electrical equipments.

Very good selectivity related to upstream circuit breakers and back up

protection fuses.

Wide range of DB s and consumer units for ease of installation.

C.2.6.TECHNICAL DATA OF A MCB:

VOLTAGE RATINGS : 415V AC

CURRENT RATINGS : 0.5 TO 63A

SC BREAKING CAPACITY : 10KA

RATED FREQUENCY : 50 – 60 Hz

SPECIFICATION : IS/IEC:model number.

MOUNTING : Clip on DIN 35mm rail

INSTALLATION POSITIO : Vertical/horizontal.

AMBIENT TEMPERATURE : -5C TO +55C

C.3. MPCB14

C.3.1.INTRODUCTION:

MPCB refers to MOTOR PROTECTION CIRCUIT BREAKERS. In

machine tools, textile machineries, automobile, food and many other process industries

compact devices are required for disconnection and protection of plant and individual

loads. Although such loads are of smaller ratings, the protection devices still have to

have adequate short circuit breaking capacity. Further the devices should be compact, for

simple, efficient and suitable for maintenance free installation. The MPCBs have proved

themselves in such applications.

C.3.2.OPERATIONS:

C.3.2.1..DISTRIBUTION FEEDER PROTECTION:

The fixed short circuit release can be offered for disconnecting and protecting

the distribution feeders. Closer protection can be offered for various loads.

C.3.2.2.TRANSFORMER PROTECTION:

For protection of transformers on primary side having rated currents up to

20A MPCBs having ranges 0.16 to 20A are offered. The short circuit ratings are changed

in this case and are of instantaneous type. Thus they allow switching on in rush current

peaks up to 3 times the rated current.

C.3.3.PRINCIPLE:

MPCBs operate on the Current limiting principle. In case of a short circuit,

the contacts are opened electro dynamically by the short circuit current. The

instantaneous over current release, through the switching mechanism, trips all the three

poles of the breaker. The three poles can be connected in parallel to the fuses. In the

event of one fuse blowing, the breaker gets actuated through its release and offers

tripping signal through its auxiliary contacts, to the motor control device for switching off

the motor. Thus the motors are not subjected to single phasing and costly motor burn

outs are prevented. As like other circuit breakers a large arc voltage is built up.

C.3.4.FEATURES:

15

The breaker has a trip free mechanism and

tripping cannot be prevented by the toggle switch position.

Space saving compact modular design.

Integrated auxiliary contacts save space and time.

Additional auxiliary contacts are available as an add on block.

Phase failure protection.

Ambient temperature compensation up to 55degrees

Material resistant to temperature extremes.

Strict safety and quality standards ensure reliable

operation in all possible applications.

Can be used as a main and EMERGENCY STOP

switch.

Positive ON/OFF indication through toggle switch.

High rated insulation voltage.

Identical accessories reduce stock levels.

Box terminals ensure connections even with

different conductor cross section.

C.3.4.1.CURRENT LIMTING OPERATION:

The MPCBs are short circuit proof for rated continuous currents and so no

back up fuses are required. If the short circuit at the point of installation is greater than

the breaking capacity of the circuit breaker then only back up fuses are required. For this

purpose a current limiter is placed in series with the breaker which increases the

switching capacity.

When a short circuit occurs the limiter trips and breaks the current paths, as

well as the series connected circuit breaker. The short circuit causes the limiter contacts

to open, due to current separation forces, as well as by the electro magnetic high speed

trip mechanism, and remain open. The welding of the current limiter contacts via a self

closing spring is prevented. After clearing the fault which caused the short circuit, the

limiter must be reset by hand before the breaker is switched on again. This prevents

inadvertently switching onto a still present short circuit.

16

Thus by this operation the following protection are attained:

Short circuit proof up to 50KA

Weld free by means of contacts which remain open after tripping

Reclosing lock out after a short circuit has occurred.

An isolating module is present which can be padlocked in either

connected or disconnected position.

C.3.5.ADVANTAGEOUS ACCESSORIES:

Shunt release for remote tripping.

Under voltage release to prevent restarting of the motor when the supply

returns

Under voltage release with 2 leading auxiliary contacts, which in the open

position avoid accidental energization to the control circuit

Remote switching module can be switched ON and OFF remotely.

Short circuit signaling contacts which signals a short circuit trip.

C.3.6.TECHNICAL DATA OF MPCB:

NO. OF POLES : 3

RATED VOLTAGE : 690 AC V

RATED FREQUENCY : 50 HZ

RATED IMPULSE : 6 KV

RATED BREAKING CAPACITY : 10 KA

MAX. RATED CURRENT : 25A

C.4. BIMETAL OVERLOAD RELAYS

17

C.4.1.INTRODUCTION:

The bimetal relays are indigenously manufactured and bring to the users a

whole range of benefits, which are as a result of extensive research and development

efforts in design, materials and manufacturing technology. They enclose a built in single

phasing protection. In conjunction with contactors and other motor control equipment,

they provide accurate and reliable protection to motors against overload and single

phasing. They also offer protection against unbalanced voltages.

C.4.2.OPERATIONS:

The bimetal relays are ideal for heavy starting applications, when heavy

masses are to be put in motion with the resultant long starting period. In conjunction with

the contactors and other motor control equipment, they provide accurate reliable

protection to motors, with an acceleration time up to 30 sec and starting current up to 6

times the rated current, against overload and single phasing.

C.4.3.PRINCIPLE:

The relays offer single phasing protection by differential slider principle.

The relays work on the same principle like MPCBs but they can’t act upon short circuit

unless they are suffixed with motor protection equipments. They can efficiently act upon

overload and protect (single phasing protection).A bimetal relay has a bimetallic strip

which are in contact under normal load conditions. In case of abnormalities i.e. overload

the coil gets heated up which heats up the bimetallic strips and they produce an opposing

magnetic field and are forced to separate by this. Thus the relays protect against overload

by tripping but an arc will be developed which can be avoided by differentiating into

partial arcs and quenching them effectively using the arc chutes. In case of short circuit

relays can trip the circuit only if they are suffixed with SC protection devices. This is the

basic difference between MPCB and overload relays.

C.4.4.CONSTRUCION:

They comprise of 3 saturable current transformers, a resistance unit and a

special bimetal relay connected to the secondary wing of the C.T. It is a composite unit

18

with bimetal relay mounted on the C.T.s. The saturable transformers linearly transform

the current up to approximately twice the set current, but above this value the transformer

gets saturated and the secondary current is proportionally less. Thus the relays permit

heavy starting conditions of motors and offer dependable protection against overload.

C.4.5.FEATURES AND ADVANTAGES:

C.4.5.1.BUILT IN SINGLE PHASING PROTECTION:

Relays offer single phasing protection against overloads as explained by their

principle.

C.4.5.2.TEMPERATURE COMPENSATION:

The relays are temperature compensated between their service temperatures of

-25degree and 55 degree.

C.4.5.3.SHORT CIRCUIT PROTECTION:

The relays protect themselves against overload up to 10 times the maximum

setting. Beyond this i.e. in the short circuit zone, the relays must be protected by a short

circuit protection devices.

C.4.5.4.OTHER FEATURES:

Shrouded auxiliary terminals increase safety as they protect against

accidental contact with the live parts.

Ready to wire terminals and captive screws reduce wiring time. The

screws being captive do not fall out. Hence the relays are delivered with

untightened terminals i.e. ready to wire condition. This eliminates the

operation of untightening terminals before wiring.

Funnel shaped cable entrances reduce wiring time by facilitating quick

location of the connecting wire.

A simple accessory for converting contactor mounting relay to individual

mounting.

Cable End Stops reduce wiring and testing time as they decide the

insertion depth of the connecting wire. As the wire cannot now protrude

19

into the relay housing, it does not hamper the movement of the

auxiliary contacts.

Further since the insertion depth is predetermined insulation of the cable

can be cut accordingly and the possibility of insulation getting caught

under the terminal is avoided.

In addition it comprises of recessed dial for easy setting, a change over

from manual reset to automatic reset mode, a test button, an adaptor to

convert contactor mounting relay to individual mounting, a protective

covering to avoid tampering of the setting, a trip indicator to indicate

tripped state of the manual reset relay, a reset cord to reset relay and

connecting links.

Potential free 1NO+1NC contact arrangement is provided as a standard

feature. The 1 NO contact can be used for various applications such as

annunciation.

C.4.6.TECHNICAL DATA:

RATED INSULATION VOLTAGE : 690V

RATED IMPULSE : 6KV

HEATING : Direct

RATED THERMAL CURRENT : 6A

C.5 HRC FUSES

C.5.1.INTRODUCTION:

20

HRC fuses have been developed for industrial applications specifically. They

offer protection against lighting and heating circuits. They are available in various

ranges for specific purposes and the three types are termed as bolted type, continental

type and round head type.

C.5.2.PRINCIPLE:

HRC Fuses work on a similar principle like a circuit breaker. It lets passage in

circuit along its path and its just a link in a circuit. In case of abnormality i.e overload

passing through the circuit the fuse blows and the circuit breaks. Due to special design

they give high rupturing capacity combined with low temperature rise under normal

load conditions. The quick acting characteristics of the fuses ensure that under the worst

fault conditions, cut off occurs before the maximum value of fault current is reached,

thus reducing electro magnetic and fire risk. Thus as in case of any circuit breaker

contacts bounce in case of abnormalities.

C.5.3.CONSTRUCTION:

The fuse links consist of one or more elements contained in a ceramic barrel

of exceptional strength and filled by a carefully -graded, chemically purified silica. The

end of cartridges are closed by non-ferrous electro-tinned and caps which are forced on to

the precision ground barrel under pressure, thus entirely eliminating the use of cement

with its attendant disadvantages. The fuse elements are made of copper/silver composite

type and manufactured with great care for safety.

C.5.4.FEATURES AND ADVANTAGES:

As mentioned earlier HRC fuses are available in different ranges for

specific purposes namely

1. 2-800A in Bolted type(BS)

21

2. 6-630A in Continental type(DIN)

3. 4-63A in Round Head type(RH)

They have an excellent AC and DC performance.

Watt loss will be very less in HRC fuses i.e. power loss won’t be much

because the fuse blows immediately once its an abnormal condition and

breaks the circuit.

A fuse puller is available for safe removal of fuses.

They have a breaking capacity of 80KA with fusing factor greater than

1.5, thus meeting the wiring regulations for close over current protection

in connection with PVC insulated cables.

C.5.5 TECHNICAL DATA :

CURRENT RANGE : 32 A ,63 A, 100A

AC VOLTAGE : 600 V AC

DC VOLTAGE : 600 V DC

SPECIFICATION : IS/IEC model number

BREAKING CAPACITY : 80 KA

C.6 FUSE SWITCHES

C.6.1. INTRODUCTION:

22

Fuse switches are designed for diverse applications and can be easily mounted

in switch boards for power distribution thus making them user friendly. They are

suitable for heavy duty applications of switching under no load and also under stringent

conditions of switching highly inductive loads.

C.6.2. PRINCIPLE: The principle of fuse switches is that during abnormalities it assists the

reversal of current at all the contacts thus helps in contact opening thereby giving a

positive indication of contact separation. The contact system is so designed that it can be

closed on faults and can carry fault currents till the fuses clear the faults. Thus the

working of fuse switches during fuse blows supplement the work of fuses until the

normal condition is regained back to be kept in hold state.

C.6.3.CONSTRUCTION: The complete mechanism explained above is enclosed in a fully mounted

body with excellent combination of mechanical and electrical properties. Adequate

phase barriers are provided for maximum protection. All switches are designed for base

mounting. All steel components are zinc plated, and all current carrying parts are silver

plated.

C.6.4.FEATURES:

C.6.4.1.OPERATING MECHANISM :

Front handle operation makes possible concise and smaller panels. Sturdy

operating handle incorporates features such as fool proof cover locking, inter lock defeat

facility, and padlock facility for safety locking in OFF conditions. Telescopic adjustable

handle shaft is provided for maximum flexibility in order to suit varied positions and to

make them compatible to the bus bars.

C.6.4.2.CONTACT MECHANISM :

23

The contact system comprises of spring loaded, butt type contacts. They are

multi fingers in higher ratings. Due to multiple fingers, each section carries only a

fraction of the total current. Only two per phase are subjected to make-break. Hence the

contact life of the rest of the fingers is quite high and the switch maintains low energy

losses through out its life.

C.6.4.3.OTHER ADVANTAGEOUS FEATURES:

Fuse switches are particularly advantageous in ring distribution network

where the network is fed from both sides.

High short circuit making capacity –the contact system is so designed

that it can be closed on faults and can carry fault currents till the fuses

clear the faults.

Fuse links are stationery-prevents loosening of fuses, high mechanical

endurance, longer fuse life.

Easy wiring-The switches have facility of wiring without removing any

fuse carrier or mechanism. No extra shrouds are needed.

Suitable for use in AC and DC operations.

Positive indication of contacts and it is suitable for surface mounting.

C.6.5.TECHNICAL DATA OF FUSES:

STANDARD CURRENT RATING: 32A

TYPES : FSB,FSC

INSULATION VOLTAGE : 660V

SC CAPACITY : 80KA

C.7 CONTACTORS24

C.7.1. INTRODUCTION:

Contactors are of two types basically:

Power contactors

Auxiliary contactors

Power contactors are suitable for switching and controlling squirrel cage and

slip ring motors as well as other AC loads, such as solenoids, capacitors, lighting loads

and transformers. Auxiliary contactors are suitable only for lighter load applications.

Though their applications differ their principle of operation is the same.

C.7.2. PRINCIPLE:

The basic operation of a contactor is to hold the contacts in a control circuit. In

case of abnormality as in any other case the contacts should bounce. It has a coil

wounded inside its frame. In case of normal condition or the coil gets energized as a

result the contacts are now in NC i.e normally closed condition. On the other hand in case

of abnormality i.e overload or short circuit the coil gets de energized and the contacts

lose their hold and they are now in NO i.e normally open state. Its not a case of NC and

NO important thing is contacts bounce under abnormality.

C.7.3.CONSTRUCTION:

Contactors have a superior design of the current carrying parts, contact system

and the magnet system. This provides high starting currents in case of power

contactors. It has a finger touch proof design. This design can even be extended to its

auxiliary contacts. The arc chambers are enclosed inside them and this ensures no direct

arc emission. The contacts are double break parallel bridge contacts which is a unique

feature of power contactors in specific.

C.7.4.FEATURES AND ADVANTAGES:

25

C.7.4.1.UNMATCHED PERFORMANCE AND RELIABILITY:

Severe operating conditions, such as high starting currents and long run up

times of motors call for increased dynamic withstand capacity and

greater short time ratings. Superior design makes such applications easy.

The use of superior material offers increased operational reliability

through long electrical and mechanical endurance.

C.7.4.2 HIGH DEGREE OF SAFETY TO PERSONNEL AND PLANT

Contactors satisfy the conditions for positively driven operation between

the main power contacts and the NC contacts i.e. NC contacts positively

open before the main contacts close.

Closed construction of arc chambers ensures no direct emission of arc by

products on the surrounding equipment.

Power contactors of larger ratings if used without arc chambers, can cause

serious accidents to the maintenance personnel and the surrounding

equipment. A mechanical interlock preventing closure of contactor if the

arc chamber is not fixed in place completely eliminates such possibility.

Switching of contactors without arc chambers is sometimes resorted to

because of their breakages. The use of superior material avoids breakages

and consequently switching the contactors without arc chambers is

prevented.

C.7.4.3.ELECTRONIC COMPATIBILITY AND RELIABILITY:

A double break parallel bridge contact is a unique feature of the

contactors. This ensures an extremely high reliability and compatibility in

electronic circuits.

Surge suppressors are available as accessories to limit the voltage surges.

Thus the contactors can be safely used in conjunction with electronic

circuits.

C.7.4.4.SIMPLE AND QUICK HANDLING:

26

Mechanical switching position indicator provides visual indication of the

closed state of the contactor.

The indicator is delatched from the moving contact bridge to avoid

electrical closing of the contacts with manual pressing.

The contactors are suitable for connections with flat bus bars or cable lugs.

Shrouded terminals are available which save wiring space, terminal lugs

and wiring time.

C.7.4.5.MECHANICALLY INTERLOCKED CONTACTORS:

In applications involving reversing feeders for crane control and

installation on machines where vibrations are experienced by the

contactors these type of contactors are used. A mechanical interlocking kit

and electrical wiring diagram is maintained for such applications mostly

star delta applications.

C.7.5 TECHNICAL DATA :

RATED INSULATION VOLTAGE : 1000 V

SERVICE TEMPERATURE : -25OC TO 55OC

RATED IMPULSE STRENGTH : 8 KV

MAXIMUM OPERATING VOLTAGE : 1000 V

SUPPLY COIL FREQUENCY : 50 HZ

1. TEMPERATURE CONTROLLERS27

1.1 INTRODUCTION:

Any production process involves various temperature requirements at specific

points. Its not possible to produce a very high temperature from an existent room

temperature all of a sudden and then there may be a requirement of extremely low

temperature immediately. But the temperature requirement of a process is of vital

importance which cannot be surpassed or given in short. A temperature controller helps

in such situations. Both analog and digital types are available in accordance with the

flexibility of the operator.

1.2 PRINCIPLE :

Temperature controllers get their input from temperature sensors either RTD

or thermocouple. According to the temp, RTD resistance value changes which is fed in to

the temperature controllers and in turn temperature controllers convert resistance into

temperature. Each set point in a temperature controller is associated with a relay. In case

of process temperature more than the set point value the corresponding relay glows and 28

the contacts change from NO to NC which activates a load in particular solenoid valve

whose contacts are changed on glow of the relay. There are Standard tables available for

resistance vs temperature.

In case of thermocouple as input, millivoltage is the input for the temperature

controller and it converts into temperature. Like the previous case if the process value is

less than a set point its corresponding relay glows changing the contacts and activating a

solenoid valve or any load

STANDARD RESISTANCE vs TEMPERATURE TABLE (pt100)

TEMPERATURE (C) RESISTANCE ()

0 100.00

50 119.40

100 138.50

150 157.31

200 175.84

250 194.07

300 212.02

350 229.67

400 247.04

450 264.11

500 280.90

550 297.39

600 313.59

1.3 CONSTRUCTION :

A temperature controller accepts signals from a variety of temperature sensors

like RTDs and thermocouples to maintain the required process temperature. It is

29

constructed with a black plastic alloy case and collar style panel latch. This kind of

assembly is termed as Bezel assembly. The advantage of this assembly is that the circuit

boards can be removed from the case to change the output board without removing the

case from the panel or disconnecting wiring.

1.4 DESCRIPTION :

The temperature controllers used in the plant are of PID type which

abbreviates for Proportional Integral Derivative. Its output signals mainly range 4 to 20

mA or 0 to 10 V DC signals. It precisely displays the process temperature, and

provides the appropriate output control signal to maintain the process accurately at the

desired temperature. The controller operates in PID control mode for both heating and

cooling, with on demand auto tune, which will establish the tuning constants. A value is

being set at the beginning and the process temperature increases or decreases

proportionally to the set value, sets more than the set value initially and then integrates

itself to reach the set value ultimately. The PID tuning constants may be fine tuned by the

operator at any time and then locked out from further modification. The controller

employs a unique over shoot suppression feature, which allows the quickest response

without excessive overshoot. The controller may also be programmed to operate in the

ON/OFF control mode with adjustable hysterisis.

1.5 FEATURES :

Temperature controllers are very compact in their size approximately 1/16

Din.

Dual LED displays provide Simultaneous Indication of process

temperature and set point (the lower display selectable for set1, set2, set3

which are nothing but set value displays, % output, ramp set point (o C / o F) everything displayed in the same controller.

Proportional Integral Derivative controls with Reduced overshoot.

On demand Auto tuning of PID control settings.

Relay (a kind of sensor which provides a reflex action on activation to be

described later ) can be programmed as heat/cool alarm.

Heat/cool PID algorithm provides a step by step process.

Single point ramp soak algorithm.

30

Auto/manual mode can be switched according to situation.

Soft start (Set point ramping for process start up)

Universal input; accepts sensor inputs (thermocouple or RTD)

Digital filtering times 0 to 99 second and it has a high indication accuracy

of + or - 0.25%

In case of any errors in sensors temperature controllers compensate it with

an offset. So it detects sensor break.

Status indicators are available for output indication.

Parameter security through programmable lock outs is provided in

controllers.

1.6 OPTIONAL FEATURES :

Dual 4 digit displays allow viewing of the process temperature and set

point simultaneously.

Optional alarms can be configured to activate according to a variety of

actions( Absolute high or low, Deviation high or low, band IN or OUT,

and Heater Current break) with adjustable hysterisis.

A stand by feature suppresses the alarm during power up until the

temperature stabilizes outside the alarm region.

Optional Linear DC output can be used for control or retransmission

purposes.

Optional Heater Current Monitor provides a direct read out of process

heater current. An alarm can be programmed to signal when the heater has

failed. This provides early warning of system failure before product

quality is affected.

Optional Remote Set point input allows for multiple ganged controller

operation for large oven and extruder applications; allows for cascade

control loops, where tighter control is required; and allows for remotely

driven set point signal from computers or other similar equipment.

An optional serial communication interface provides two way

communication between a PID and other compatible equipment such as a

Printer, PLC, or a computer. In multipoint applications the address

number of the PID has to be programmed suitably. Data from PID can be

31

interrogated or changed, and alarm outputs may be reset by sending the

proper command code via serial communications. PC software is available

for configuration of controller parameters. These settings can be saved to

disk for later use or used for multi controller downloading.

1.7 SPECIFICATIONS:

1. DISPLAY : Dual 4 digit (7 segment LED)

Upper Display : Red LED (process value)

Lower Display : Green LED (selectable)

Display messages:

“OPEn” - Appears when measurement exceeds range or open sensor is

detected.

“tCrE” - TC reverse

LED Status Annunciators:

Relay on

Alarm

Manual mode

2. SETTINGS : Via four keys on the front panel

3. MEMORY :Nonvolatile EEPROM retains all programmable

parameters

4.MAIN CONTROL:

Control : PID or ON/OFF

Output : Time proportioning or Linear DC

Cycle time : Programmable

Auto-tune : When selected, sets proportional band, Integral time,

Derivative time, Cycle time and other parameters.

5. AUXILIARY OUTPUTS (ALARMS) :

Modes : Direct, Reverse, Heat-cool.

Operates : either Absolute or Deviation value

32

Hysterisis : Programmable

Reset-Action : Programmable; automatic or latched.

6. HEAT-COOL PID MODE:

Control : PID or ON/OFF

Output : Time proportioning

Dead band

Overlap : Programmable

7. ENVIRONMENTAL CONDITIONS :

Operation : 0 to 500C

Storage : -20 to 750C

Humidity : 85% max. relative humidity(non condensing at all points)

8. RELAY ACTION:

a) Heat mode

b) Cool mode

33

2. PROXIMITY SWITCHES

2.1 INTRODUCTION:

Proximity switches are solid state switching devices which require no physical

contact to actuate them. They are used for controlling and positioning signals. They can

be directly connected into conventional or electronic control systems. There are two types

of proximity switches :

1. Inductive type (Specifically for metal parts)

2. Conductive type (Used for any conductive materials)

2.2 PRINCIPLE:

The electronic proximity switch comprises of three principle parts:

1. The oscillator

2. A trigger stage

3. Amplifier stage.

The oscillator generates, with its coil, a high frequency electromagnetic field

of approximately spherical distribution. Any metallic object introduced into this field

absorbs energy from the oscillator by induced eddy currents. This reduces the

amplitude of the oscillations and this change triggers the output stage. This type of

oscillator will respond to any type of metal.

2.3 DESCRIPTION :

34

2.3.1 SENSING FACE :

The sensing face of a proximity switch is the surface from which the

electromagnetic field radiates.

2.3.2 SENSING DISTANCE :

The sensing distance is the maximum distance between the target and the

sensing face to be sure of obtaining a switching signal. This distance is measured using a

square mild steel. The sides of the square target should be equal to the diameter of the

sensing face of the proximity switch.

The Nominal sensing distance is a reference dimension only and does not

take into account temperature or voltage variations.

The Effective sensing distance is the distance measured at nominal voltage

and ambient temperature.

The Usable sensing distance is measured within a given voltage and

temperature range.

The Working sensing distance is every sensing distance which guarantees

operation under given temperature and voltage conditions. The distance can be selected

between 0 and the usable sensing distance.

2.3.3 REDUCTION FACTOR :

If the target of the proximity switch is manufactured from a material other

than mild steel or if the target varies in thickness and area from the standard target, then

the sensing distance will vary.

2.3.4 SWITCH HYSTERISIS:

The switch hysterisis is the difference between the switch ON point, when the

target approaches the sensing face of the proximity switch and the switch OFF point,

when the target moves away from the sensing face.

2.3.5 TEMPERATURE DRIFT :

The temperature drift is the change in switch point due to variations in

ambient temperature conditions when all other conditions remain constant.

35

2.3.6 REPEAT ACCURACY :

It is the reproduction accuracy between two successive operations under the

same ambient conditions

2.3.7 ELECTRICAL CHARACTERISTICS :

1.VOLTAGES :

The operating voltage is the voltage which can be used to operate the

proximity switch.

The voltage drop is the voltage measured between the energized output

and the switched potential at the rated current of the switch.

The ripple voltage is the AC voltage superimposed on the mean DC

voltage expressed as a percentage. Maximum ripple is absolutely essential

for effective operation of DC switches. When using a single phase

rectified supply the appropriate smoothing capacitor should be used.

2.CURRENTS :

The load current is the maximum current at which the proximity switch

can be continuously operated.

The Inrush current is the maximum current which can flow, from the

moment the switch is on, for a specified time

The No-load current is the current consumed by the switch at the

maximum operating voltage without there being any external load current.

The residual current is the current which flows through the load even

when the switch is in its blocked state

Holding current is the least current necessary to ensure correct

functioning of an actuated wire switch.

3 LIMIT SWITCHES

3.1 INTRODUCTION:

Limit switches are used in automatic control circuits where mechanical

positions have to be converted into electrical signals for controlling remote starters,

36

contactors etc. They are ideally suited for control of machine tools, elevators, cranes,

conveyors, gates, doors and various other applications. These limit switches are actuated

by straight edges, cams, stops or plates etc. and give control commands for further

progress of the switching program or of the manufacturing/processing sequence. For the

various control applications there are two ranges available :

Open type limit switches

Metal enclosed limit switches

3.2 PRINCIPLE :

A limit switch consists of a fixed and a movable contact. In a normal

condition the fixed contact will be in NC and the movable contact in NO. The purpose of

a limit switch is that if any cylinder comes in contact with the roller of the limit switch

the contacts will change i.e fixed contact will now become NO and movable NC

A spring which is placed inside the switch will be compressed when a

cylinder pushes its roller. So when it is plunged down NC contact will be separated as it

pulls down and the movable contact which is initially open will now be closed. By this

way if any cylinder moves out of the way limit switches will bounce its contacts for the

cylinder to step back to the normal line. In case of jamming of crates limit switches

bounce its contacts, and the signal from the contacts is fed to the PLC. Then PLC creates

a small delay time and the crates gain back their normal gaps. Each contact is associated

with two screws which takes care of the spring movement. Many types of limit switches

are available. The number of contacts may vary for different types but the principle

remains the same for all the types.

3.3 CONSTRUCTION:

Open type limit switches are intended for use of auxiliary switches in

cabinets, large enclosures or locations not affected by dust or moisture. The open type

switches are available with 2 or 3 sets of contacts. They have been offered various degree

of protection against foreign bodies.

Limit switches have stipulation of mounting dimensions, operating points,

housing form and actuator form. The metal enclosed limit switch consists of the housing,

37

contact block and the actuator. The contact block is placed within the housing. It

comprises of moving double contact pieces, spring plate (carries the moving double

contacts without rigid mechanical connection) and terminals.

3.4 DESCRIPTION:

1. PLUNGER ACTUATION:

A stainless steel hardened plunger with telescopic action is precisely guided

within anodized die- cast light alloy head, and is practically maintenance free. This plain

bearing principle ensures reliability. The direction of actuator head can be changed in

steps of 900.

2. DIAPHRAGM SEAL:

In switches with plunger actuation, the plunger area separated from the switch

chamber by a diaphragm seal made from elastomer. The seal is practically indestructible.

The seal is firmly fixed to the plunger and is returned to the free position after each

operation, not by the switching element but by the plunger return spring. Any

development of pressure due to plunger actuation is eliminated by a relief valve. The

switching element is actuated by a metal cap pressed on to the seal. Switching point

displacements are therefore completely eliminated.

3. LEVER-ARM ACTUATION:

Three different levers can be used on the lever arm actuated switches. The

stainless steel shaft is precisely guided through housing. The numerous adjusting

possibilities are:

Adjustment of the actuator head around the longitudinal axis is possible

in 900 steps.

Adjustment of the lever arm in positively fixed positions is possible in

900 steps.

Infinite adjustment of the lever arm within 3600.

Adjustment of the switching direction.

3.5 FEATURES:

38

A wide range of actuators are suitable for different operations enabling the

user to select the most optimum one for particular application.

Specially designed compact housings allow optimum installation and

convenient cable entry.

The design, materials used and manufacturing processes ensure reliable

functioning of control and auxiliary systems.

All contact blocks have a black moulded plastic housing, in which the

fixed contacts and terminals are accommodated.

Interior of the metal enclosed switches comprises of a plastic slide with

moving contacts, which perform double contact interruption. The contact

set and switching chamber are protected by means of a guard.

The standard metal housings along with the corresponding actuators

conform to the Din accommodation.

The metal housings are corrosion resistant and unaffected by shocks,

impact and hot liquids.

The housings are in complete degree of protection (complete safety from

finger-touch/protection against hazardous effects of water, when

immersed in it).

The wide housing has longitudinal holes to the left and the right of the

actuator. This allows adjustment of operating point during installation, in

case this adjustment cannot be performed via the actuating element, this

housing has 3 threaded holes for contacts cable entry, which makes it

more versatile with regard to connection possibilities, as available space is

also greater.

The actuators and contact blocks can be interchanged depending on the

application.

The switching direction of limit switches with roller crank or adjustable

length roller crank can be changed by re-positioning the internal plunger.

3.6 SELECTION OF LIMIT SWITCHES:

1.OPEN TYPE:

The open type switches can be used in dry, dust free environments such as

switch boards and closed cubicles.

39

2.IN HOUSING:

If moisture and mechanical/thermal stresses (like shocks, impact) occur, the

metal enclosed position switch must be used.

3.ACTUATORS:

The selection of actuators differs with respect to permissible actuation

direction, actuation speed, form of actuation element and the advantageous

combination of components. All switches function independently of their

installation position. The same mode of selection applies for contact blocks

also. Under no circumstances may the limit switch be used as a mechanical

stop on a moving section of a machine.

3.7 TECHNICAL DATA:

RATED INSULATION VOLTAGE : 500 VAC; 600 VDC

RATED THERMAL CURRENT : 10A

HOUSING MATERIAL : Aluminum die-cast

AMBIENT TEMPERATURE : -400C T0 +850C

4 TIMERS

4.1 INTRODUCTION:

Timers are devices designed for creating time delays in many ways. The delay

produced by the timer activates a relay at its end period.

40

4.1.1 TYPES OF TIMERS:

Timers are of various each with their own functions:

On delay timers

Interval delay timers

Pulse output timers

Repeat Cycle equal (OFF first) timers

Repeat cycle equal (ON first) timers.

Delay on break timers

Delay on make with totalize (time storage)

Interval after break

Interval with totalize

Interval on make/interval on break

Retriggerable single shot

4.2 PRINCIPLE OF OPERATION :

4.2.1 ON DELAY:

When input power is applied timing begins, during which the output relay

remains de-energized. At the end of the pre-selected time, relay energizes. The output

relay is de-energized when the power is removed, thus resetting the timer for the next

cycle.

RESET:

Removing input voltage resets the time delay and output relay.

4.2.2 INTERVAL DELAY:

Applying the power supply starts the time delay and the output relay gets

energized. At the end of the preset time, the contact gets de-energized. The timer is reset

when the input power is removed.

4.2.3 PULSE OUTPUT:

41

Applying the power supply starts the time delay, during which the output

relay remains de-energized. At the end of the preset period, the relay gets energized for a

preset time. At the end of preset time again relay de-energizes.

4.2.4 REPEAT CYCLE EQUAL (OFF FIRST):

Upon application of input voltage, the output relay remains de-energized and

time begins. At the end of the time period, output relay energizes for set time. At the end

of time again de-energizes and this cycle continues until input voltage is removed.

4.2.5 REPEAT CYCLE EQUAL (ON FIRST) :

Upon application of input voltage, the output relay energizes and time begins.

At the end of the time, output relay de-energizes for set time. At the end of time, again

relay energizes and this cycle continues until input voltage is removed.

4.2.6 DELAY ON BREAK:

Input voltage must be applied before and during timing. Upon application of

input voltage, the output remains de-energized. On closing the control contact the output

energizes. The time delay begins when control contact is opened. The output remains

energized during timing. At the end of the time delay the output de-energizes. The output

will energize if the control contact is closed when input voltage is applied.

RESET:

Re-closing the control contact during timing resets the time delay. Removing

input voltage reset s the time delay and output.

4.2.7 DELAY ON MAKE WITH TOTALISE (TIME STORAGE) :

Input voltage must be applied before and during timing. The output is de-

energized before and during the time delay. Each time the control contact is closed, the

time delay progresses; when it opens, timing stops. When the amount of time control

contact is closed equals the full time delay, the output energizes and remains energized

until reset.

4.2.8 DELAY ON MAKE/DELAY ON BREAK :

42

Delay on make time delay and delay on break time delay are same. Upon

application of input voltage and closure of control contact, Make time delay begins and

the output remains de-energized. At the end of Make time delay, the output energizes.

Upon the opening of control contact break time delay begins. At the end of break time

delay, the output de-energizes.

RESET:

1. If control contact is opened during, Break time delay, then it is reset and

the output remains de-energized.

2. If control contact is closed during break time delay then time delay is reset

and the output remains energized. Removing input voltage resets the time

delay and output.

4.2.9 INTERVAL AFTER BREAK :

Input voltage must be applied before and during timing. Upon application of

input voltage, the output remains de-energized. On opening (after a closure), the control

contact the output energizes and time delay begins. The output remains energized during

timing. At the end of time delay the output de-energizes.

RESET:

Opening the control contact during timing resets the time delay. Removing

input voltage resets the Time delay and output.

4.2.10 INTERVAL WITH TOTALISE (Time Storage) :

Input voltage must be applied before and during timing. The output is

energized before and during the time delay. Each time the control contact is closed, the

time delay progresses; when it opens, timing stops. When the amount of time control

contact is closed equals the full time delay, the output de-energizes and remains de-

energized until reset.

4.2.11 SINGLE SHOT :

Input voltage must be applied before and during timing. Upon momentary or

maintained closure of the control contact the output energizes and time delay begins. At

43

the end of the delay the output de-energizes. Opening or re-closing the control contact

during timing has no effect on the time delay.

RESET:

Reset occurs when the time delay is complete and the control contacts is open.

Removing input voltage resets the time delay and output.

4.2.12 RETRIGGERABLE SINGLE SHOT :

Input voltage must be applied before and during timing. Upon momentary or

maintained closure of control contact the output energizes and the time delay begins. At

the end of the delay the output de-energizes.

RESET:

Re-closing control contact resets the time delay and restarts timing. Removing

input voltage resets the time delay and output.

4.2.13 START DELTA TIMER :

Star contactor closes and the set run up time starts when the supply voltage is

applied. Mains contactor is switched on via the auxiliary contacts of start contactor and

then becomes self holding via its own auxiliary contacts. Simultaneously, auxiliary

contacts of mains contactor open, thus connecting the timer and the start contactor via its

auxiliary contacts to the supply. Other contacts 15/16 DIN open after the run up time,

thus switching off the supply voltage of the timer and of the start contactor. This contact

remains open for sometime and resets after that time to ensure that start contactor has

opened. Delta contactor is connected via auxiliary contacts of star contactor.

4.3 FEATURES :

Compact size (1/16 DIN)

Slim, space saving construction.

Finger guards for safety

Repeat accuracy better than 0.5 %

44

On delay / Interval user selectable

Special timer for star-delta change over.

Fixed change over time in start delta timer

Timers have a strong mechanical and electrical life.

4.4 TECHNICAL DATA :

DELAY MODES : On delay / Interval

Cyclic ON first / Cyclic OFF first

RESET INPUT : 1.Front panel reset

2.Remote reset

3.On power interruption.

LED INDICATION : Relay Status

MOUNTING : Panel mounting

HOUSING : Flame retardant engineering plastic

5 UV DISINFECTION UNIT

5.1.INTRODUCTION:

Light is electromagnetic radiation or radiant energy in the form of waves.

Ultraviolet energy is found in the electromagnetic spectrum between visible light and x-

rays. Two different UV wavelengths are employed in water treatment the 254 nm and

185 nm. 254nm UV light is employed in Disinfection and Ozone destruction

applications. It penetrates the outer cell-wall of the microorganism, passes through the

cell-body, reaches the DNA and alters the genetic material. The microorganisms are

therefore destroyed.

5.2.PRINCIPLE:

UV light obeys the laws of electromagnetic radiation, including the de

Broglie’s principle and Einstein’s laws. When a molecule absorbs the incident UV

radiation, it gains energy. The extent of energy absorption depends upon the wavelength

of the radiation – the lower the wavelength, the greater the gain in energy. When

45

organisms absorb UV light in the range 200-300nm, the UV light is absorbed by DNA

and RNA molecules. The DNA molecule contains all the genetic information needed for

replication. UV absorption causes disruption of the nucleic material of the double helix

strands. This prevents replication, which is lethal to the cell. Dimers opposing the normal

formation are formed. Thus if the UV dosage is not optimized, complete inhibition of

replication will not occur. On the other hand, an insufficient UV dosage may cause

limited damage to the DNA, which the cell can, under favorable conditions, repair using

repair enzymes. So it is extremely critical to impart optimum UV dosage in order to

prevent repair. While bacteria have built-in repair enzymes, viruses do not. Therefore,

they have to rely on the enzymes of the host cell.

5.3 CONSTRUCTION:

UV components are designed based upon flow rate capacity. Each model is

designed for a maximum flow rate, based upon application, water quality, water

temperature and other factors. A UV unit comprises of:

Sample ports

Treatment chamber

Quartz sleeves and Lamps

Drain port

Control cabinet.

1 Quartz sleeves provide a barrier between the UV lamp and the water.

Special manufactured quarts material allows the passage of the UV

radiation that provides the energy to destroy the micro-organism.

Alternative sleeves should not be used.

2. Compression Nut provides a compression for the sealing of the quartz

Sleeve.

3. Lamp Cap ensures the lamp socket to the compression nut, the lamp cap

is provided.

4. Lamp Socket provides electrical power to the UV lamp. This socket

should never be removed during operation of the UV unit.

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5. O-Ring provides the seal for quartz sleeve. The material is specially

specified to withstand UV energy, heat, ozone and other elements in

contact with the unit.

6. Two optional sample and drain ports are available for obtaining water

samples pre and post the UV treatment chamber. Sanitary sampling valves

should be installed on the ports. Each treatment chamber is provided with

a drain port to complete drainage of the treatment chamber. A drain valve

should also be installed.

5.4 DESCRIPTION :

A typical UV unit comprises a cylindrical chamber featuring UV lamps

encased inside quartz sleeves arranged within the chamber, with the water flowing over

the sleeves. The quartz sleeves run through helical baffles designed to promote turbulent

flow, which enhances the contact and increases residence time, thereby resulting in

increased dosage and absorption of UV radiation. The baffles help to break the bacterial

colonies entering the UV unit and also help to insure turbulent flow pattern.

The optimized engineering of the lamp configuration within the cylinder

allows for optimization of the transmission of UV light to every part of the cylinder. The

lamps are securely held in place by a lamp retainer assembly. The water stream flows

across the cylinder through the inlet/outlet connections. During the few seconds that the

water resides within the cylinder, the targeted contaminants present in the water (bacteria,

TOC, ozone etc. ) absorb the incident UV radiation generated by the lamps. The targeted

MEDIUM

Fluid

EnergyInto The Field

EnergyEmitted By TheUV Source

Optical Path

47

contaminants are thereby destroyed and the water stream rendered purer. The inside

surface is made of stainless steel, passivated and electro-polished to specifications. The

stainless steel is sheared, fabricated, welded and then dye-checked for welding integrity.

The process of passivation involves a series of steps including several hot nitric acid

baths, followed by hot DI water rinses that render the material bright and inert.

5.5 FEATURES :

Each of the UV units is furnished with a non-resettable running time meter.

It is used to determine the number of hours on the equipment and for

maintenance. It is very important to record the running time hours and

lamp maintenance.

To verify the status of the UV lamps, the LED display gives the operator a

visual indication of the lamp status. When the UV light is ON, the LED

will illuminate.

There are two basic components: the sensor and the controller. The UV

sensor is a combination temperature and UV probe. Semiconductor signals

are processed within the sensor and sent via a cable to the controller. The

sensor is provided with O-ring which is necessary to create the proper

seal.

UV lamps produce heat. The heat within the chamber must be dissipated to

prevent damage to the UV unit and water system. Under normal operating

conditions, the water flow is sufficient to remove heat generated by the

lamp. In process conditions in which there may be no flow conditions,

temperature controller is available. When the temperature exceeds the UV

lamps automatically switch off, preventing overheating conditions.

The sensor provides information about the relative amount of UV passing

through the water and the absolute intensity of UV. It reflects changes in

UV transmission when a substantial change occurs in normal operating

flow rate, temperature or quality of fluid flowing through the system.

When the UV intensity falls below the minimum standard, remote

interferencing will be activated for which corrective action has to be taken.

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UV controller has the capability to display continuously the level of

irradiance detected by the sensor. It reports the current temperature value

of water.

6 FLOWMETERS

6.1 INTRODUCTION :

Electromagnetic flow-meters with signal converter are designed solely for

measuring the volumetric flow rate of electrically conductive, liquid process products i.e

they are useful for flow measurement of liquid products. It is mainly designed for

electrically conductive fluids.

6.2 PRINCIPLE :

Flow measurement is based on Faraday’s law of induction, according to which

a voltage is induced in an electrically conductive body which passes through a magnetic

field. The induced voltage is proportional to the mean flow velocity, when the field

strength is constant. Inside the electromagnetic flow meter, the fluid passes through a

magnetic field applied perpendicular to the direction of flow. An electric voltage is

induced by the movement of fluid (which must have a minimum electrical conductivity).

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This is proportional to the mean flow velocity and thus to the volume of flow. The

induced voltage signal is picked up by two electrodes which are in conductive contact

with the fluid and is transmitted to a signal converter for a standardized output signal.

6.3 CONSTRUCTION :

A flow meter mainly comprises of flow head, flow converter and display.

Water flows through the flow head and magnetic field is generated. According to

Faraday’s principle signal converter converts the impulse into readable meter signals

which is displayed in the display placed in front of the panel.

6.4 DESCRIPTION :

The magnetic field of the primary head is generated by a square wave current

fed from signal converter to the field coils. This field current alternates between positive

and negative values. Alternate positive and negative flow rate-proportional signal

voltages are generated at the same frequency by the effect of magnetic field, which is

proportional to the current. The positive and negative voltages at the primary head

electrodes are subtracted from one another in the signal converter. Subtraction always

takes place when the field current has reached its stationary value, so that constant

interference voltages or external or fault voltages changing slowly in relation to the

measuring cycle are suppressed.

6.5 ADVANTAGES :

This method of measurement offers the following advantages :

No pressure loss through pipe constriction or protruding parts.

Since the magnetic field passes through the entire flow area, the signal

represents a mean value over the pipe cross section; therefore, only

relatively short straight inlet pipes are required upstream of the primary

head.

Only the pipe liner and the electrodes are in contact with the fluid.

The original signal produced is an electrical voltage which is an exact

linear function of the mean flow velocity.

Measurement is independent of the flow profile and other properties of the

fluid.

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7 PLC’S

7.1 INTRODUCTION :

Programmable Logic Controllers (PLC’s), also referred to as

programmable controllers, they are in the computer family. They are used in commercial

and industrial applications. A PLC monitors input, makes decision based on its program,

and controls output to automate a process or machines.

7.2 PRINCIPLE OF OPERATION :

PLCs consist of inputs modules or points, a Central Processing Unit (CPU),

output modules or points. An input accepts a variety of digital or analog signals from

various field devices (sensors) and converts them into a logic signal that can be used by

the CPU. The CPU makes decisions and executes control instructions based on program

instructions in memory. Output modules control instructions from the CPU into a digital

or analog signal that can be used to control various field devices (actuators). A

programming device is used to input the desired instructions. These instructions

determine what the PLC will do for a specific input. An operator interface device allows

process information to be displayed and new control parameters to be entered.

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7.3 FEATURES :

Prior to PLCs, many of the control tasks were solved with contactor or relay

controls. This is often referred to as hard- wired control. Circuit diagram’s has to be

designed, electrical components specified and installed, and wiring lists created.

Electricians would then wire the components necessary to perform a specific task. If an

error was made the wires had to be reconnected correctly. A change in function or system

required extensive component changes and rewiring

Very complex task can be done with a PLC. Wiring between devices and relay

contacts is done in the PLC program. Hard wiring though still required to connect field

devices, is less intensive. Modifying the application and correcting errors are easier to

handle. It is easier to create and change a program in PLC than it is to wire and rewire a

circuit.

The Central Processor Unit (CPU) is a microprocessor system that contains

the system memory and is the PLC decision-making unit. The CPU monitors the inputs

and makes the decision based on instructions held in program memory. It is more or less

like a C.P.U of a computer. The C.P.U performs the functions of relay, counting, timing,

data comparison, and various sequential operations

PROGRAMMING DEVICE

OPERATOR INTERFACE

INPUT MODULE

CENTRAL PROCESSING UNIT

OUTPUT MODULE

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7.4 ADVANTAGES :

Smaller Physical size than hard-wire solutions.

Easier and faster to make changes.

PLCs have integrated diagnostics and override functions.

Diagnostics are centrally available.

Applications can be immediately documented.

Application can be duplicated faster and less expensively.

.

E.1 SIPART PID CONTROLLER

1 -Negative deviation display2 -Replaceable label

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3.1 -LED for alarm A13.2 -LED for alarm A24 -Digital display for w-x-A2-A1 and for parameters and configurations5.1 -Manipulated variable adjustment in manual mode in direction of 0%5.2 -Manipulated variable adjustment in manual mode in direction of 100%6 -Digital display of manipulated variable from -9 to 109%7 -point lights up in S controllers when (δy is switched through)8 -Selector for digital display 4, for activation of parameterization /configuring and

for lamp test9.1 -LED lights up if w is output in display 49.2 -LED lights up if x is output in display 410 -Selector for manual/automatic mode11 -LED lights up in manual mode, flashes with external intervention12.1-Key to increase the internal set point12.2-Key to decrease the internal set point13 -Selector for internal/external set point14 -LED lights up with internal set point, flashes with certain operating states.15 -Cover for scale replacement.

E.2 BLOCK DIAGRAM OF RATIO CONTROLLING LOOP

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E.3 RATIO CONTROLLING PROCESS

E.3.1 INTRODUCTION:

SYRUP FLOW METER

DISPLAY SYRUP FLOW

PRODUCTFLOW METER

DISPLAYPRODUCTFLOWSIPART

SYRUP IN PRODUCT OUT

DRD VALVE

4-20 mA

SYRUP IN

CONTROLLED SYRUP OUT

MIXINGDEVICE

WATER IN

PRODUCTOUT

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In ratio controlling process following components are used :

Syrup and beverage flow meters

Ratio Controller (SIPART)

Modulating valve

E.3.2 DESCRIPTION:

1. SYRUP FLOW METER -It measures the syrup flow and gives 4-20 mA signal to

Ratio controller.

2. BEVERAGE FLOW METER -It measures the beverage flow and gives 4-20 mA

signals to Ratio controller.

3. RATIO CONTROLLER -During lemonade production the ratio of syrup in beverage

is set in this controller and according to that it controls the syrup modulating valve.

4. MODULATING VALVE -It operates according to the 4-20mA signal from Ratio

controller.

E.3.3 RATIO CONTROLLING PROCESS:

According to the product, ratio has to be set on the Ratio controller. As soon

as the production starts, Ratio controller gives fixed output to the modulating valve.

Beverage and syrup flow meters measure the flow and accordingly give current output to

the Ratio controller. It compares both the feed back signals with the set value and

generates the error signal in such a way that the difference between the actual value and

set value reduces in progressive steps. The generated error signal is then converted into

controlled air by i/p converter of the syrup modulating valve. According to the controlled

air the Syrup modulating valve increases or decreases the syrup flow. The actual valve

opening and deviation in actual value with respect to the set point is displayed on the

Ratio controller. There are two deviation in +ve and –ve. For any reason if the deviation

remains continuous for more than 30 sec the machine will stop.

E.4 BLOCK DIAGRAM OF TEMP

CONTROLLING PROCESS

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E.5 TEMP. CONTROLLING PROCESS

57

E.5.1 INTRODUCTION:

In temperature controlling process following components are used:

Plate Heat Exchanger (PHE)

RTD Sensor

Temperature controller (SIPART)

Modulating Valve

E.5.2 DESCRIPTION:

1. PHE – The glycol and Beverage is passed through this unit. It is used to cool the

beverage.

2. RTD SENSOR-It measures the temperature of the beverage and gives signal to the

temperature controller

3. TEMPERATURE CONTROLLER-The required beverage temperature is set in this

controller. It takes the actual temperature feedback from the RTD sensor according to that

it controls the Glycol Modulating valve.

4. MODULATING VALVE-It operates according o the 4-20mA signal from SIPART

E.5.3 TEMPERATURE CONTROLLING PROCESS:

The required beverage temperature has to be set on the SIPART. As soon as

the production starts, SIPART gives fixed output to the modulating valve. The RTD

sensor measures the beverage temperature and accordingly gives output to the

temperature controller. It compares the feedback signal with the set value and generates

the error signal. The error signal is then converted into controlled air by i/p converter of

the valve. According to the controlled air the Glycol modulating valve changes its

opening, which changes the glycol flow. The controlled glycol then passes through PHE.

The beverage which flows through PHE comes in contact with the controlled glycol. In

PHE temperature transfer takes place between glycol and beverage. The actual valve

opening and deviation is displayed on SIPART.

SPECIAL PROJECT

58

AUTO AIR CONTROL SYSTEM (ON/OFF) FOR

DATE CODING MACHINE

1 AIM:

The purpose of designing this system is to avoid flow of air from the system

when there is no production or when no bottles are being sensed by the proximity sensor

before date coding is done. In short air should flow only when a bottle is sensed by the

system. Its principal application is to remove moisture from the body of a bottle by

blowing air where date coding will be done.

2 CIRCUIT BLOCK DIAGRAM:

3 COMPONENTS USED:

24V DC Power Supply

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Proximity Switch (operating voltage 0 to 30 V DC)

24V DC Relay

Off Delay Timer (coil voltage 220V AC)

24V DC Solenoid Valve ( Coil 24V DC)

4 DESCRIPTION OF THE CIRCUIT:

A 220V AC supply is fed to a step down transformer and converted into

24VAC. This 24V AC supply is rectified with the help of diodes into 24V DC. A

capacitor is used to give a pure 24V DC supply. Positive of the 24V DC is connected to

positive of a Proximity switch and negative of the 24V DC is connected to negative of the

Proximity switch.

Output from the proximity switch is connected to the relay coil where as other

end of the relay coil gets supply directly from negative of 24V DC supply. When the

proximity switch senses the bottles in the line before date coding relay coil gets energized

and the relay gets activated now. Supply for common of the relay is given directly from

positive of 220V AC supply. Output from relay is connected to A1 terminal which is the

P terminal of a timer coil. N terminal or A2 terminal of timer coil gets supply from

negative of 220V AC supply.

Timer coil gets energized and it activates the timer. Positive of 24V DC is

connected to common of the timer and output from timer is used to energize a solenoid

coil. Output from timer is connected to positive of solenoid coil and negative of solenoid

coil gets supply from negative of the 24V DC directly. Solenoid coil gets energized and

activates a solenoid valve through which air blows out.

This completes the circuit for air control system which blows air out through

the solenoid valve when there is a sensing of bottle and remains idle when there is no

sensing.

5 OPERATION:

As mentioned earlier the aim of the system is to blow air only when bottles

are sensed and to remain idle otherwise. When a bottle comes out after filling and

capping its outside is moisturized because beverage is being filled at a very low

temperature which moisturizes the bottle.

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Immediately after filling and capping date and time of manufacture has to be

printed on the bottles. As the bottles are moisturized immediate flash of prink ink on it

causes poor printing which appears blurred. To clean outside of the bottles incase some

beverage has flown out some water is being sprinkled near the neck where date has to be

printed. Placing this air control system after sprinkling will wipe out the moisture and

date can be printed clearly.

When a bottle comes after sprinkling of water on its outer part the proximity

switch senses the arrival of bottle. The proximity is activated by the 24V DC power

supply. Proximity output energizes relay coil whose negative supply is obtained directly

from the 24V DC. Relay coil being energized now relay gets activated. Output from relay

is used to energize the coil of timer whose negative gets supply directly from 220V AC.

The timer coil being energized it activates the off delay timer.

The timer now energizes a solenoid coil. The solenoid coil on energizing

activates a solenoid valve. Timing is being set on the timer. Solenoid valve opens and air

blows out of it until the timing interval is set. Once the timing interval is over timer is

reset and air flow stops if there are no bottles in the line and proximity doesn’t sense any

bottle.

The principle of solenoid valve is that when coil is energized it activates the

valve. It consists of an inlet and an outlet opening for passage of air through it. When

solenoid is energized plunger moves up and provides provision for air passage through

the valve or else if the coil is de-energized the plunger closes the valve and air flow stops.

G.UTILITIES IN THE PLANT

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G.1 CIP PANEL:

Digitronik SDC150 PID Temperature controller (steam valve controlling)

Radix TCD4000R make Caustic tank Temperature indicator

Radix TCD4000R make Hot water tank Temp indicator (2 limit)

G.2 PARAMIX :

Siemens make SIPART ratio and temperature controllers

Syrup flow indicator AP lab 1006-SP

Product flow indicator Fuji make

Electromagnetic flow meter (Khrones make each for beverage and syrup)

Simatic S7-300 PLC SYSTEM.

G.3 FILLER :

Siemens simatic S5 PLC SYSTEM

E + H make Conductive level probes.

E + H make Level Control switch

Danfoss Variable Freq. Drive for main drive.

Proximity switches (P & F make ) used for various applications.

G.4 CASER AND UNCASER :

Simatic S5 PLC SYSTEM

Proximity switches

Retro reflective sensors

Pneumatic cylinders.

Solenoid valves (Single and double acting )

Pressure switches

G.5 BOTTLE WASHER:

Libratherm make PID 8000 6 zone temperature controller

Libratherm make BPM meter

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Allen Bradley Variable Frequency drive.

Pneumatic cylinders

5/2 and 3/2 Festo make solenoid valves.

RTD s

G.6 COMBINER PANEL:

Siemens Simatic S7-300 PLC SYSTEM.

Danfoss make VLT5000 Variable Frequency Drives

Pilz make voltage scanner.

G.7 CHILLING PLANT:

Radix pyratech ektra 4SP temperature controller

Radix DT1 350 Temperature Indicator

Audiotronics temperature indicator

Differential Pressure switches

RTD s

H.CONCLUSION

63

On the whole this project report gave away a lion’s share to instruments

mostly specific to electrical and instrumentation engineers. A detailed study on all the

instruments taken into account has been reported. On this basis what one comes to know

is that instruments though are of more or less a similar principle each finds its application

for specific purposes where the aliters can’t gain their entry.

The electrical layout presented at the beginning gives a detailed idea of how

power is distributed to the plant and what is the requirement for each of the equipments

under lying. As seen from the layout it starts from the state electricity supply and then

how the plant distributes the total supplied power. A good knowledge of this distribution

will help an electrical engineer to control any abnormalities.

The instruments dealt in this project though new to study, a practical

knowledge of each of them provides a very good under standing of its every aspect. On

the whole personally I have gained a good knowledge of all the various above listed

instruments and how power is being distributed to this plant.

My second course of study included all the electronic instruments their

principles and operations in detail. Based on the study of all the instruments I practically

designed an auto air control system for Date coding machine in the plant which is of very

much importance to avoid lot of air loss and subsequently power loss. My circuit design

and the operation of design have been presented in the report. The very basic thing I have

learnt is “Know safety no pain- No safety know pain” is all the instruments are about.

REFERENCE :

Book on Electrical instruments by Nagrath and Bobrow

Microprocessors by Douglas Hall

Various study manuals and some reference from howstuff works.com

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