Corrosion Test chamber

Introduction

Thermal corrosion Cycling is an innovative and cost effective process of enhancing the mechanical properties of many materials commonly used in commercial and industrial technologies. Thermal Cycling has been determined to significantly increase the corrosion properties of many ferrous alloys. The salt spray test is a standardized test method used to check corrosion resistance. Salt spray testing is an accelerated corrosion test that produces a corrosive attack to the tested samples. The appearance of corrosion products (oxides) is evaluated after a period of time. Test duration depends on the corrosion resistance of the tested material. Salt spray testing is popular because it is well standardized and reasonably repeatable. The correlation between the duration in salt spray test and the expected life of a material is not necessary simple to interpret as corrosion is a very complicated process and can be influenced by many external factors. Nevertheless, salt spray test is widely used in the industrial sector for the evaluation of corrosion resistance of finished surfaces.

Background

Salt spray was first used for corrosion testing around 1914. This traditional salt spray specifies a continuous exposure to a 5% salt fog at 35o C. In spite of all se refinements, re has long been general agreement that “salt spray” test results do not correlate well with corrosion seen in actual atmospheric exposures. As demand for improved corrosion protection increased, engineers and scientists attempted to develop test procedures to more accurately predict corrosion of materials. In England, during 1960’s and 1970’s, Harrison and Timmons2, 3 developed ProhesionTM test, which has been found especially useful for industrial maintenance coatings. More recently, Society of Automotive Engineers (SAE) and American Iron and Steel Institute (AISI) have been studying testing for automotive applications. ir progress has been encouraging and is well documented.4, 5, 6, 7, 8, 9, 10 Japanese researchers have also developed a number of corrosion test methods.

What is Corrosion Testing?

The corrosion testing is intended to be a more realistic way to perform salt spray tests than traditional, steady state exposures. Because actual atmospheric exposures usually include both wet and dry conditions, it makes sense to pattern accelerated laboratory tests after se natural conditions. Research indicates that, with corrosion tests, relative corrosion rates, structure and morphology are more similar to those seen outdoors. Consequently, tests usually give better correlation to outdoors than conventional salt spray tests. y are effective for evaluating a variety of corrosion mechanisms, including general, galvanic, and crevice corrosion. corrosion testing is intended to produce failures representative of type found in outdoor corrosive environments. CCT tests expose specimens to a series of different environments in a repetitive cycle. Simple exposures like Prohesion may consist of cycling between salt fog and dry conditions. More sophisticated automotive methods call for multistep cycles that may incorporate immersion, humidity, condensation, along with salt fog and dry-off. Originally, se automotive test procedures were designed to be performed by hand. Laboratory personnel manually moved samples from salt spray chambers to humidity chambers to drying racks, etc. More recently, microprocessor controlled chambers have been used to automate se exposures and reduce variability.

Block Diagram:

Essential features of system –

Above system is use for simulating atoms passerine condition switch will be required for taking life tests for spares rsed in any mechanical or automobile industry. As already mentioned in block diagram explanation enclosure dominations are given here. Such type of corrosion test ambens are available in tapana tools ltd Nasik Bajaj auto ltd pune tata pune hero Honda etc. also in motor manufacturing industry se are essential

1. This project should not be run direct under sun-light 2. Air supply given should be proper, purified and

regulated.3. water supply should also be pure and feel3 mixing

proportion should be appropriate

TempController

Thermocouple

Power supply

4. Air and water supply should be continuously to no22le

Parameter settings required

Ten up range =

1. 25c ------- 30c2. 30c ------- 40c3. 35c-------- 60c

For maintaining same heat should be operated properly add a digital temp indicated should be provided

Compressor air pressure should be 7kglcm2

Air passed air pressure setting at air pressure result being control unit is 5to6 kglcm2

Technical data

Approximate done sud be if unit

1. With =200mm2. Height=300mm3. Depth=450mm

Main supply -230vac at 50hz

Compressor air – 4.6bar above atmospheric pressure.

Water supply connection -1-3 bar above at –morphemic pressure

Specimen holder tray :- specimen holder to is located inside corrosion chamber in such a way i.e. it will be a net which will be suitable to provide moisture to tally

material used for chamber will be properly painted or powder coated so as to avoid corrosion effect salt

About nozzle spray no22le – spray nozzle is key point of system . It is used for spraying moisture in test chamber.

Our approach o this point is hat , it should make automizer readily accessible to operator and being of simple two part construction, easily dismantled for cleaning purpose. But blockages have remain an unavoidable and irritating fact of life until w here are developing a new design of auto miser which makes blockages a thing of past.

Pl. follow figure given,

atomizers made up of simply disassembled for cleaning and maintenance. Manufactured in one of new generation of high performance plastics, it features an ingeniously designed integral salt solution filter inb car parted into body of atomizer.

This works in conjunction with a profit located in salt solution reservoir, to ensure that even smallest contaminants or undisclosed salt cryss will not reach and block automiser. filter can be easily removed and washed clear of contaminant whole n being reassembled and reinstalled in cabinet, quickly and conveniently .

nozzle is mad up of aluminum metal which is also non corrosive in nature and easy machining.

After assembly, spray nozzle will have two main connections i.e.

1. One inlet for water supply2. Anor inlet for air supply 3. Moisture output as a spray

Fixture Arrangement :

The fixture assembly that brings all of the system together. These come in a variety of configurations, vertical, horizontal, tabletop, freestanding, or mobile cart. Implementation details:

1. Initially, all the ms angle of calculated dimensions in mm was taken.2. Then it was cut into pieces as per the required dimension3. All these angle pieces were joined together to form top side frame of the

basic structure.4. Another ms angle with required dimension was taken 5. It is cut into pieces to form a leg pieces 6. Fabricate the legs with the rectangle from one by one to form the stand

structure.

OPERATIONS INVOLVED

Turning

Facing (flat surface)

Drilling

Gas cutting

Shaping

Welding

Tapping

Thread cutting

TURNING

Turning is the operation of reducing a cylindrical surface by removing material from the outside diameter of a work piece. It is done by rotating the work piece about the lathe axis and feeding the tool parallel to the lathe axis. Due to this operation screw rod and head are done by the turning operation to get the required shape.

FACING

Machining the end of the work piece to produce flat surface is called facing. Due to this, the plate can get flat surface have done by the facing operation.

DRILLING

Drilling is the operation of producing cylindrical hole in work piece. It is done by rotating the cutting edge of the cutter known as drill bit. In this Project the jig plates require holes for locating indexing plate and screw rod, drill bush assembly. These holes are done by conventional vertical drilling machine.

THREAD CUTTING

Thread cutting is the operation of forming external thread of required diameter of rod by using a multipoint tool is called thread. This process is used in screw clamp to done on the rod which is used for the movement of the movable plate

FINE GRINDING

It is nothing but the grinding process, which is done as smooth with fine grains. This is done as the each plate and base plate for good surface finish. It is done by conventional grinding machine.

GAS CUTTING

It is used to break are cut the plates. In this project it is used to cut the raw materials such as plates. This done by gas cutting machine.

SHAPING

Shaping operation is used to reduce the dimensions of the plates. In this project the plates are in need of shaping process. It is done by shaping machine.

WELDING

It is the process, which is used to join two, is more similar materials as well as dissimilar materials. In this project it is used to join the jig plate one to another. This is done by arc welding machine.

Scope of work:

The machines have been designed to support human beings by helping them to do tedious and back breaking works. However, the industry has made only the limited use of high technology production concept. There is general need to nature the development program in automation and robotics. Machines have been employed in various tasks including material handling various interior and exterior finishing task, including material handling the high expectations of the stemmed from the very serious problems the industry is facing

Continuous declining productivity A high accident rate. Low quality In sufficient control of construction site Vanishing of skilled work force.

In recent years the use of new technologies within the industry has shown great potential although little has been implemented. For example robatic systems and other programmable machines are needed to perform tasks that involve hazardous of rate or in some way physically dangerous to human the development of robotics systems in construction advance very slowly owing to several challenges one of the obstacles in the development of the required software component such development for highly trained programme and export software engineers.

Chamber Environments:

Non-ambient environments are usually chamber exposures. Cycling between different non-ambient environments can be performed by physically moving the test specimens from one chamber to another or, in automated chambers, by cycling from one condition to another. The temperature and relative humidity should be monitored. Whenever possible, automatic control systems should be used. Temperature tolerances should be ±3°C or better.

Fog (Spray) Environment:

Salt fog application can take place in a laboratory ambient environment. The fog nozzle should be such that the solution is atomized into a fog or mist. Commonly, in addition to NaCl, the electrolyte solution contains other chemicals to simulate acid rain or other industrial corrosives.

Humid Environment:

CCT procedures often call for high humidity environments. Typically they specify 95 to 100% RH. These may be achieved by using hot water air and salt spray chamber may sometimes be used to apply a pure water fog.

TEMPERATURE SIGNAL CONDITIONING

Process Transducers:-

Transducer converts one form of energy into another form. In

our case the physical energy is to be converted into an electrical signal. For

temperature we use Thermocouples as a transducer .Thermocouple works of

seeback effect principle i.e. when two dis-similar metals are fused together and

heated milivolts are generated at another end. We use J-type i.e. Fe-con as a

thermocouple which uses ferrous & constantan as two dis-similar metals. The

milivolts generated at particular temperature are as below.

0mv – 0°C

1.28mv – Ambient Temperature

5.23mv – at 100°C

10.77mv – at 200°C

16.32mv – at 300°C

21.8mv – at 400°C

This milivolts signal is given as an input to the signal

conditioning block for further processing.

Analog Signal Conditioning:-

In analog signal conditioning operational amplifiers are used.

The electrically received form the transducer is converted to a proper range.

Thermocouple Conditioning:-

Please follow the circuit diagram as below.

Circuit Diagram

As shown 4 operational amplifier configurations are there. For

thermocouple sensor, cold junction compensation is to be done. We are adding

the milivolts signals corresponding to ambient temperature here. One ambient

sensor is used. 2N2222 is a transistor having two diodes connected together

inside. We use one of the diodes among the two. As shown this CJC diode sensor

is connected in series with the conducting transistor.

This transistor is mode ON by providing the biasing vtg at it

base. This biasing voltage should be above 0.7v. A potential divider with two

different resistors is used here.

This divider has resistors -

R1 = 12 K & R2 = 7K5, input = 5vdc; Vout =?

R2

Vout = -------------- Vin

R1 + R2

7k5

Vout = ------------------- x 5vdc.

12k + 7.5k

Vout = -------------- > 0.7V

During calibration, this sensor is allowed to sense atmospheric

temperature. In such situation the output from the transistor emitter is fed to the

non-inverting terminal of the operational amplifier. The inverting terminal is

provided with a variable signal. This variable signal is provided using a variable

divider as below.

R1 Rx R2

- Vcc + Vcc

2k2 10k 2k2

Vout Vout

Here, +Vcc = +5vdc and – Vcc = - 5vdc.

The total voltage drop = (+5v – 0v – -5V) = 10V. This low dc is

divided across the potential divider of R1, R2 and Rx.

Thus, the voltage signal at the variable terminal of the variable

potentiometer can be varied as per the requirement. As this signal is fed as an

input to the inverting input of the amplifier, the output of amplifier changes

depending upon any of the input either inverting or non-inverting. Initially 300mv

are adjusted at the central point i.e. wiper of potentiometer. The op-amp being

in unity gain fashion, generates – 300mv at the output. The signal is equivalent to

30°C. Thus, if no signal from thermocouple section, output should be equal to

30°C. Once this is set, the atmospheric changes are sensed by the ambient sensor

and are shown on LCD module. This is cold junction compensation section.

Thermocouple sensor is connected at the input of difference

amplifier. Reference the mv generation table of the sensor as given earlier.

Suppose we calibrate the unit up to 100°C, we require 2000mv as an input to

ADC. As 20mv = 1 unit on LCD. Thus, 5.23mv is converted into 2000mv. We do

the amplification in two steps. At initial difference amplifier.

5mv are converted to 100mv i.e. means a gain of 20 is required

here, for difference amplifier.

- RF

Vout = -------------- (V2-V1)

R1

- RF

Thus, Vout = -------------- (5mv Say) – Let R1 = 10k

10k

- RF

100mv = -------------- (5mv)

10k

RF = 200k

But, 200k being not available we use 220k here. Also, a multi-

tern trimpot is provided for getting a flexible gain. Thus, the signal available at

the output of difference amplifier and the signal available at CJC output are added

together in adder amplifier.

Please follow the figure.

R1 = 10k

Vout = 2.600mv

Vin = 130mv.

Here, also we require the gain = 20, hence in summing

amplifier.

R1 = 10k, and RF = 220K again.

Thus, we get the appropriate output which goes to ADC. If we

connect thermocouple the output varies linearly from ambient to maximum as

per the change in temperature.

Temperature Calibration:-

Before using any digital process instrument it should be

calibrated properly. Standard calibrators are required for this purpose. These

calibrates are required for this purpose. These calibrators are also certified by the

national committee such as NABL, ETDC… etc.

The steps involved in calibration are given as under

1) Initially, short the thermocouple input and adjust ambient temperature

equal to 30°C, with the help of multi-turn potentiometer.

2) Then connect milivolts source at thermocouple input and set the

milivolts input = 5.23mv and set the output equal to 100°C + 30°C

ambient, i.e. total – 130°C with ‘span’ potentiometer.

3) Repeat above (1) and (2) steps sequentially till we get output = ambient

= 30°C and maximum = span = 130°C.

Spray Nozzle:

A spray nozzle is a precision device that facilitates dispersion of liquid into a spray. Nozzles are used for three purposes: to distribute a liquid over an area, to increase liquid surface area, and create impact force on a solid surface. A wide variety of spray nozzle applications use a number of spray characteristics to describe the spray.

Spray nozzles can be categorized based on the energy input used to cause atomization, the breakup of the fluid into drops. Spray nozzles can have one or more outlets; a multiple outlet nozzle is known as a compound nozzle. Single-fluid or hydraulic spray nozzles utilize the kinetic energy of the liquid to break it up into droplets. This most widely used type of spray nozzle is more energy efficient at producing surface area than most other types. As the fluid pressure increases, the flow through the nozzle increases, and the drop size decreases.

Many configurations of single fluid nozzles are used depending on the spray characteristics desired.

Relay:

A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such assolid-state relays. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays"

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that activates the armature, and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.

Pressure RegulatorPressure regulating components are formed by various components, each of which has its own pneumatic symbol:(i) Filter – can remove impurities from compressed air before it is fed to the pneumatic components.(ii) Pressure regulator – to stabilise the pressure and regulate the operation of pneumatic components(iii) Lubricator – To provide lubrication for pneumatic components

POWER SUPPLY

Rectifier Filter3 TerminalVtg. Regulator

Power supply is the first and the most important part of our project.For our

project we require +5v regulated power supply with maximum current rating

500 mA

Following basic building blocks are required to generated power supply.

230vac Reg.o/p

STEP DOWN TRANSFORMER :

Step down transformer is the first part or regulated power supply . To step down the mains 230V A.C. we require step down transformer. Following are the main characteristic of electronic transformer.

I) Power transformer are usually designed to operate from source of low impedance at a single freq.

II) It is required to construct with sufficient insulation of necessary dielectric strength.

III) Transformer rating are expressed in volt-amp. The volt-amp of each secondary winding or windings is added for the total secondary VA. To this are added the load losses.

IV) Temperature rise of a transformer is decided on two well known factors i.e. losses on transformer and heat dissipating or cooling facility provided unit.

RECTIFIER UNIT:

Rectifier unit is a ckt. Which converts A.C. into pulsating D.C. Generally semi-conducting diode is used as rectifying element due to its property of conducting current in one direction only Generally there are two types of rectifier.

1. Half wave rectifier2. Full wave rectifier.

In half wave rectifier only half cycle of mains A.C. rectified so its efficiency is very poor. So we use full wave bridge type rectifier, in which four diodes are used. In each half cycle, two diodes conduct at a time and we get maximum efficiency at o/p.

Following are the main advantages and is advantages of a full-wave bridge type rectifier ckt.

ADVANTAGES :

1. The need of center tapped transformer is eliminated.2. The o/p is twice that of center tap circuit for the same secondary

voltage.3. The PIV rating of diode is half of the center taps circuit.

DISADVANTAGES :

1. It requires four diodes.2. As during each half cycle of A.C. input, two diodes are

conducting therefore voltage drop in internal resistance of

rectifying unit will be twice as compared to center tap circuit

Filter circuit :

Generally a rectifier is required to produce pure D.C. supply for using at various places in the electronic circuit, However, the o/p of rectifier has pulsating character i.e. if such a D.C. is applied to electronic circuit it will produce a hum i.e. it will contain A.C. and D.C. components. The A.C. components are undesirable and must be kept away from the load. To do so a filter circuit is used which removes (or filter out) the A.C. components reaching the load. Obviously a filter circuit is installed between rectifier and voltage regulator. In our project we use capacitor filter because of his low cost, small size and litile weight and good characteristic. Capacitors are connected in parallel to the rectifier o/p because it passes A.C. but does not pass D.C. at all.

A voltage regulator is a ckt. That supplies constant voltage regardless of change in load current. IC voltage regulators are versatile and relatively cheaper. The 7800 series consists of three terminal positive voltage regulators. these ICs are designed as fixed voltage regulator and with adequate heat sink, can deliver o/p current in excess of 1A. These devices do not require external component. This IC also has internal thermal overload protection and internal short circuit and current limiting protection for our project we use 7805 voltage regulator IC.

D3T3 D1

+5V

1GNDD2

2GND

0-10 , 500 mA

230VAC@50HZ

+C1

D4

+C3

7805

1 3VIN VOUT

Design to step down transformer :

The following information must be available to the designer before the commences for the design of transformer.

1. Power output2. operating voltage.3. Frequency Range4. Efficiency and Regulation

Size of core :

Size of core is one of the first consideration in regard of core and winding configuration used. Generally following formula is used to find area or size of core.

Ai = (p1/0.87)

Where

Ai = Area of cross section in sq. cm.

7812

P1 = Primary voltage

In Transformer P1 = P2

For our project we required +5V regulated output. So transformer secondary rating is 12V, 500 mA.

So secondary power wattage is,

P2 = 12 X 500 X 10 –3 w.

= 6w.so ,

Ai = (6/0.87) = 2.62

Generally 10% of area should be added to core accommodate all turns for low Iron losses and compact size.

So,

Ai = 2.88.

Turns per volt

Turns per volt of transformer are given by relation

10,000

Turns/volt = -------------------

4.44f B Ai

Here;

F is the frequency in Hz

B is flux density in Wb/m2

A is net area of cross section.

For project for 50Hz the turns per volt for 0.91 wb/m2,

Turns per volt = 50/Ai

= 50/ 2.88

= 17

Thus for primary winding = 220 X 17 = 3800.

For secondary winding = 12 X 17 = 204

Rectifier design :

R. M. S. Secondary voltage at secondary of transformer is 12V. So, maximum voltage Vm across Secondary is

= RMS voltage *1.41

= 12* 1.41

=16.97

D.C. output voltage at rectifier o/p is

Vdc = 2Vm/3.14

= 2*16.97/3.14

= 10.80 v

PIV = 2 Vm

= 2 X 16.97

= 34V

Design of filter capacitor

Formula for calculating filter capacitor is,

1

C = -----------------------------

4. 3 r f RL

r = ripple present at o/p of rectifier.

(Which is maximum 0.1 for full wave rectifier ?)

f = Frequency of mains A.C.

R = I/p impedance of voltage regulator IC.

1

C = ------------------- = 1000F

4 3 0.1*50*28

IC 7805 (Voltage regulator IC):-

Specifications :-

Available o/p D.C.voltage = + 5V Line regulation = 0.03 Load regulation = 0.5 Vin maximum = 35 V Ripple Rejection = 66-180(db)

TESTING AND TROUBLESHOOTING

Before soldering in components:

Check that component agree with the parts list (value and power of resistors, value and voltage rating of capacitor, etc.) if in any doubt double check the polarized components (diodes, capacitor, rectifiers etc)

If there is a significant time elapse between circuit, take the trouble to read the article; the information is often given in a very condensed from. Try to get most important point out of the description of the operation of the circuit, even if you don’t understand exactly what is supposed to happen.

If there is any doubt that some component may not be exact equivalent, check that they are compatible.

Only use good quality IC sockets. Check the continuity of the tracks on the PCB (and through plated holes

with double sided boards) with a resistance meter or continuity tester. Make sure that all drilling, filling and other ‘heavy’ work is done before

mounting any components. If possible keep any heat sinks well isolated from other components. Make a wiring diagram if the layout involves lots of wires spread out in all

directions.

Check that the connectors used are compatible and that they are mounted the right way round.

Do not reuse wire unless it is of good quality. Cut off the ends and strip it a new.

After mounting the component:

Inspect all soldered joints by eye or using a magnifying glass and check them with a continuity tester. Make sure there are no dry joints and no tracks are short circuited by poor soldering.

Ensure that the positions of all the component agree with the mounting diagram

Check that any links needed are present and that they are in the right positions to give the desired configuration.

Check all ICs in their sockets (see that there are no pins bent under any ICs, no near ICs are interchanged etc.)

Check all the polarized components (diodes, capacitor etc) are fitted correctly.

Check the wiring (watch for off cuts of components leads) at the same time ensure that there are no short-circuits between potentiometer, switches, etc. and there immediate surrounding (other components or the case). Do the same with mounting hardware such as spacers, nuts and bolts etc.

Ensure that the supply transformer is located as closely as possible to the circuits (this could have a significant improvement in the case of critical signal level).

Check that the connections to the earth are there and that they are of good contact.

Make sure the circuit is working correctly before spending any time putting it into a case.

And if it breaks down:

Recheck everything suggested so far.

Re-read the article carefully and carefully anything about which you are doubtful.

Check the supply voltage or voltages carefully and make sure that they reach the appropriate components especially pins of the ICs (test the pins of ICs and not the soldered joints).

Check currents (generally they are stated on the circuit diagram or in the text). Don’t be too quick to suspect the ICs of overheating.

If possible check the operation of the circuit in the separate stages as a general rule follow the course of the signal.

While checking voltages, currents, frequencies or testing the circuits with an oscilloscope work systematically and take notes.

And don’t forget to switch the power on and check the fuses. PCB DESIGN

Designing of PCB :I) After selection of electronic circuit, make a block diagram of various

circuits to know various inter-connections required, which will help in reducing the number of wires.

II) The designer should have the complete idea of the circuit regarding the function and signal flows through.

III) Keep each and very component you need, while starting the designing.

IV) Use of templates is essential if you are new designer, if the design is manual i.e. hand made and not with software such as Orcas, Auto CAD, Pads, Ideas, Circuit maker, etc.

V) Standard PCB size should be decided in the beginning only.VI) Preferably, layout ands artwork should be in 1:2 scales.VII) Sequential stage after PCB size is decided.VIII) Component placement.IX) Track routing i.e. layout.X) Artwork making with ink or ready made tapes and pads.XI) While routing the tracks, carrying AC mains voltage, consider the

safety rules ands regulations.XII) In analog and digital systems together, care should be taken that

analog and digital ground will not mix each other affecting the stability ands fluctuations in the display.

XIII) In power system i.e. high current, the track width and the track spacing should be as maximum as possible.

XIV) While placing the components on the PCB preferably the load on PCB, should be evenly distributed to avoid the problems at completion stage during wave-soldering i.e. warping of PCB etc.

XV) To avoid weakening of the pup tool, the perforation length should be kept minimum i.e.<40 mm.

XVI) For the manually shouldered components vent i.e. cut pads should be provided to avoid the blocking of the holes during shouldering

COMPOMENT PLACEMENT :

I) Preferably, place the component in X-Y direction subjected to mechanical construction.

II) All components should be flat mounted i.e. flat placed to avoid of leads and for easy requirements. However in case of space limitation the components such as resistors, diodes, etc. may be mounted vertically which doesn’t affect the performance.

III) In case separate analog and digital ground.IV) Orientation of multi-lead components(e.g. switches, Ics)

should be connected in between the analog and digital ground .

V) Sufficient clearance is provided around component so that inversion or replacement ands repair is easy.

VI) The design should such that minimum jumpers are allowed.VII) It is preferable that, components like present, coils, and trim

pots, etc. which alignment of calibration are placed in such that, they are accessible after the assembly of the PCB on cabinet also.

If the components are not flush mounted, provide the sleeve for leads.

Advantages:

Cyclic corrosion test methods were originally developed as labor intensive manual procedures. Automated, multi-functional chambers are now available and can perform CCT tests in a single chamber. Some of the advantages of automated systems are that they:

• Eliminate manual moving of test specimens from one chamber to another

• Eliminate laborious spraying of test specimens

• Eliminate variability in results from excessive specimen handling

• Allow more predictable transition times