What is the importance of backlink and Page Rank?

The questions which we will be covering in this Zlob are What is a backlink? What are internal and external links? Why is it important to have quality backlinks? What are quality backlinks? What is page rank? And What is Dofollow and Nofollow?

What is a backlink?

In simple terms backlink is a HTML clickable link from any site to your site or website page.
The link should be the URL or web address on your page.
This simple means that if any other website puts a link from his page to any of your page in your website then it is counted as a backlink. The link can be in any form, it can be a text, picture or a button- the main thing is that by clicking on it the browser should open your page in the same window, another tab or in another window.

Micromax Canvas 4 A210 review, features and cheapest price

The whole world is getting crazy about smartphones, and to quench the thrust of this crazy addiction, mobile companies are coming up with new features in there smartphones almost every single day. Maybe this is the reason that even Micromax is also set to come up with a great peace of art and has been able to add one more star in their Canvas series. Yes, they have introduced their latest technology in their new Canvas model and that is Micromax Canvas 4. This smartphone has got a lot of new features, so let us first have a look at its specifications.

Where and how to check the status of your DMCA application at Google Webmasters-DMCA Dashboard

If you have been in the field of publishing original content online or in simple terms blogging actively for sometime now and more importantly have attracted the attention of numerous readers by your good quality content and high authority website, then you must have faced situations where people copy your content.

It is no different for me and especially since I work on revenue sharing website as a Manager where I am responsible for checking other people's article for copied content and other Google Webmaster quality guidelines I come across many such instances where I find other people copying the content from our authors. Now, since we have to approve the articles at our sites and we face some practical problems due to which we can't rely on our authors to file the DMCA with Google correctly, we Managers ourselves file the DMCAs as legal representatives of the owner of this website.

Now, the problem I used to face was that sometimes there was no reply mail from Google's side and I would get stuck about the status of my application. I had seen the Dashboard of Google and I knew that I could find the status of my application there but the problem was how to open that Dashboard. No matter how hard I tried, I couldn't find the link to the Google DMCA Dashboard anywhere. I need to add here that I did not remember the word "Dashboard" while searching for it and was typing sentences in Google search like "DMCA Google status" "Status of Google DMCA application" "Copy complain Google DMCA status" and a few more search terms like this but was not able to find it. I even searched the Webmaster tools of Google but even that does not contains the link to it.

Anyhow, just out of nowhere I luckily remembers the word "Dashboard" and when I typed "Google DMCA Dashboard", the link to the page came as the first result. So I thought why not to help my fellow bloggers in finding this precious page easily and free them from the struggle of finding this page. So here is the link to the page of Google DMCA Dashboard which if will find useful now or later if you continue to follow you passion of blogging and continue creating original and quality content for your readers.

Application of Gray, Excess-3 and ASCII codes

The ASII code:

The ASCII code represents the text in computers or digital equipments. The ASCII(American Standard Code for Information Interchange)  includes definition for 128 characters that explains the processing of text and space.

Excess-3 code:

The excess 3 code is an important BCD code. It is mainly used for arithmetic operations. It can add two decimal numbers even if their sum exceeds nine. It simplifies operations of arithmetic. It’s a way to represent decimal digits, and each value equals the decimal digit value plus 3.

Gray code:

The encoding of numbers such that the adjacent number differs by only 1 by the preceding number.

Application of Gray Code

Because of many shortcomings in addition of the BCD code, excess 3 code is used and grey code is used in the shaft position of the airplanes.

These codes are precisely used in electro optical switches and electrochemical signals.

The Grey code arises in many real life situations. In the beginning, the main use of the code was related to what we now call as the conversion from analog to digital format. The basic aim was to convert a voltage value which was previously in analog to the corresponding series of pulse which will represent the same value in digital form. This technique was to convert voltage by displacing vertically an electron beam that sweeps horizontally across the screen of the cathode ray tube. The screen having a masked imprint on it only allows a passage of beam in certain places, and a current was generated till the beam was passing through the mask. The passage of the beam gives rise to a series of ‘on’ and ‘off’ conditions corresponding to the pattern of the holes through which it passes.

The most common use of this code is locating for rotational position of the shafts I which a pattern which represents the grey code is printed on a disk, or on the shaft, and the pattern is sensed by an electrical or optical detector.

Application of Excess-3

Because of many shortcomings in addition of the BCD code, excess 3 code is used and grey code is used in the shaft position of the airplanes.

These codes are precisely used in electro optical switches and electrochemical signals.

The Gray code arises in many real life situations. In the beginning, the main use of the code was related to what we now call as the conversion from analog to digital format. The basic aim was to convert a voltage value which was previously in analog to the corresponding series of pulse which will represent the same value in digital form. This technique was to convert voltage by displacing vertically an electron beam that sweeps horizontally across the screen of the cathode ray tube. The screen having a masked imprint on it only allows a passage of beam in certain places, and a current was generated till the beam was passing through the mask. The passage of the beam gives rise to a series of ‘on’ and ‘off’ conditions corresponding to the pattern of the holes through which it passes.

The most common use of Gray code is locating for rotational position of the shafts I which a pattern which represents the grey code is printed on a disk, or on the shaft, and the pattern is sensed by an electrical or optical detector.

 

Gray Code was used in some old computers that relied on a pre-specified number N as a biasing value.

The excess 3 code is a technique to represent numbers with a balance of positive and negative numbers. When the sum of two of these excess 3 numbers exceed 9, the carry bit of adder will set to high. When you add two excess 3 numbers, the resultant would not be an excess 3 number, example  : add  1 to 3 , the answer would seem to be 7 but the actual answer should be 4, so a remedy of this problem is to subtract 3 (binary 011) if the resultant is less than decimal 10 and add 3 if the number is equal to or greater than 10.

 This needs to be done due to the fact that whenever we add two numbers, an excess value of six results in the sum. But we now that the values 0 to 15 are four bit integer and any excess to that means the sum will overflow.

Application of ASCII

They are used widely in modern computers for representing text and in other devices too that use text in man machine interface. ASCII codes work sequentially and are self complimenting. Its first application was as a seven-bit teleprinter. It is non-weighted code derived from 8421 BCD code.

Microprocessor characterization, language, instruction set and working

What is microprocessor?

A microprocessor can be defined as followed:
"A multipurpose , programmable logic device which is capable of reading binary instructions from a storage device referred to as memory, accepts data as input and process it according to those instructions and provides result as output"
A microprocessor can be considered to be electronic integrated chip or a set of chip that implements a central processor of a computer system. Microprocessor in a microcomputer resembles a brain in human body which does the functioning of controlling all the peripherals of the body. The main parts of a microprocessor are:
1) Arithmetic and logic unit
2) Central processing unit

The properties by which a microprocessor can be characterized are:
• Speed
• Word length
• Architecture
• Instruction set

When talking about the digital computers they can be classified into different groups on the basis of:
• Size
• Processing power
• Cost and
• Complexity

In this way depending upon these factors three main classes of digital computers are:
1. Micro computers
2. Mini computers
3. Main frames

Mini computers and main frames are more complex and power full than micro computers which uses only a single IC processor unlike the other two. Here minicomputer has word word length ranges from 16 bits to 32 bits and it generally uses 2 or more CPUs.

What is microcomputer?

This category of computers is characterized by it low speed and lesser restorability of data. It uses only one CPU and which is just a single chip. It has low processing power and it is generally used in personal computing and control applications.
Any device which is programmable can be represented by three fundamental components as in the figure:
• Microprocessor
• Memory
• Input/output devices

When these three parts works and interacts together to perform a given particular task it is called a system and the physical components i.e. electronic circuits for input output devices, memory unit and microprocessor chips itself are called Hardware where as the set of instructions written to perform the given task is called a program and further a set of programmes is referred to as a software which performs some pre-specified tasks. Microprocessor receives the encoded instructions then decodes and executes them. Word length of a microprocessor depends upon the width of data bus but it is independent of the length of instruction and operands which are handled by the microprocessor. The microprocessor can handle arithmetic, logic Boolean alphanumeric data. The time taken to execute the basic instructions decides the speed of the concerned microprocessor.
Also, as the microprocessor is a synchronous sequential electronic circuit some clock signals are required for execution of its each instruction so the speed of a microprocessor will also depend upon the clock frequency of the crystal used in the system. For each pulse generated by the crystal one basis instruction is executed.
Representation and organization of the data in the memory will be described in the next portion.

How memory is organized in microcomputers?

Just as the data is written on the pages of a notebook in the same the data storage in electronic memory chip cam be resembled with writing the binary digits on the semiconductor material pages upon which these binary digits are stored such that spaces occurs there after a fixed number of the binary digits and a fixed number of the lines occurs in each pages.

Generally each line in the memory is called register i.e. a collection of 8 bits given a name one byte. Such byte or the registers are arranged in sequential manner in the memory such registers occurs in groups in power of 2 for example for a memory of 1k byte, 2 to the power 10 registers or byte are grouped together. The set of instructions written by the programmer makes the microcomputer to retrieve the data from some external storage device process them and store them in memory or to give it to some external device to display it like LCD display, 8 segment display, computer monitor, speaker in case of sound signal elc.

What is a memory module?

In our further discussion over memory organization we will be using the term memory module which refers to device which stores the data. A memory module contains a fixed number of memory locations where each location contains a fixed number of bits and the number of bits in each location in called word length. To understand the memory organization let us take an example of a memory module of size (nXm) bits then its word length will be m and memory locations will vary from 0 to n-1. It is clear from this far discussion that number of data line in it will depend upon its word length i.e. larger is the word length less will be data line in it because total number of bits in it is to be fixed which is (nXm).

Microprocessor processes the data taken from outside and returns the result it again to external peripheral the devices for connecting the microprocessor to the outside is done with help of a system of hardware called input output devices I/O modules. It will be discussed in further discussion as

What is input output module/device?

As the name suggests it comprises two parts i.e. input module/devices and output module/devices.

Input devices
Provide the data to microprocessor in binary form performing the function of senses of the system to connect it with outer world. These includes keyboard, teletype and analogue to digital converter.

Output devices
Performs the function of reproducing the result obtained from processing section and decodes the binary result and produces it a form understandable to outer world. These devices includes monitor, loudspeaker, printers, LCD display etc.

Any system requires some important and basis parts for making I/O devices usable for it. That can be listed as:
1. Output port
2. Interfacing circuitry

Output port provides the points in the systems through which it may have physical connection with I/O devices for bidirectional flow of data between system and outer world. The system may have more than one input output port but only one is accessed at time whose selection is done by microprocessor itself while the direction of data flow is determined by control signal generated by the microprocessor i.e. the instruction set decides that whether data is to be transferred from system to outer devices or it is to received by a particular port.

Data which deals with microprocessor has to be in binary form to allow any processing to be carried out upon it in the similar way the data obtained from microprocessor also occurs in binary form but it is not generally understandable by outer world. Here interface circuitry converts outer signal into binary form and binary result produced by microprocessor to some other form understandable to outer devices. In this way interface circuitry connects system to outer devices. Some of the output devices are LEOS, Cathode ray tube, printer etc.

What is instruction set and language in microprocessor?

Any microprocessor understands only machine language i.e. 0 &1. But each one differs in its instruction sets. Every microprocessor has its own words, their meanings and the language that they understand. These words are formed by different combinations of basic binary digits (0 &1) called bits. In this way we can define a word as:

"The number of bits the microprocessor recognizes and processes at a time is termed as a word"

World length of a microprocessor may varies from 4 bits to 64 bits where 4 bit words are used in small microcomputers and large words having up to 64 bits are used in high speed large computers generally word is termed as byte i.e. a group of 8 bits so a 32 bit microprocessor has can be said to have a word length of 4 bytes.

For sake of convenience a group of 4 bits is termed a nibble and thus a byte is made with 2 nibbles, a lower nibble and upper nibble.

How a microprocessor works?

A microprocessor can be made to perform a specified task by the programmer with help of a set of instruction set understandable by it. The instructions are to be in binary form i.e. 0 &1 but it is difficult for the programmer to learn the instructions in binary form they are given some English like word to make easier to learn them. In this way the collection of these English like world equivalent to particular instructions constructs a language which is used by the programmer to communicate with microprocessor. This language is referred to as assembly language and programs written in this language are called assembly programs. These assembly programs are written for a specific microprocessor and as each microprocessor understands its own unique instruction set that is why the program written for machine may and may not be transferable to another one. This is a big limitation of assembly language to overcome this limitation many general purpose languages have been developed which provides the facility of transferability of the program written in these languages as they are machine independent. some of those are:
• BASIC
• FORTRAN
• PASCAL
• C And C++

These languages are closer to human understandable languages like English and are termed as high-level languages.

Different languages and their working

Machine language
At the time formation of the microprocessors designers sets some specific combination of bits and gives them certain meaning based upon their function with the help of electronic logic circuitry these are called basic instructions of the concerned microprocessor. Set of such instructions which are designed in machine are called its machine language constructed with only 0s & 1s. Likewise taking an example of microprocessor 8085 whose word length is 8 bit and has it instruction set which is nothing but a different combination of these 8 bits. it may have 256 different bit patterns which can construct 74 different instructions to perform some specific operations.

Assembly language

Although the instructions in machine language may be written in hexadecimal form but it is still a difficult task to memorize these codes for making microprocessor to perform different functions while the alpha-numerical codes are relatively easier to memorize that is why these hexadecimal codes are given some English like alphanumerical code in place of hex or binary codes. In this way language comes out to assembly language it works in the same way that machine language does and the equivalent alphanumeric codes instructions are called mnemonics

Low level languages

Both the machine language and assembly falls in this category of programming languages which are un-transferable to any other microprocessor i.e. these programs are microprocessor specific and are written for a specific chip. The programs written in low level language are to first converted into equivalent binary form to be read by the microprocessor this function of conversion is done either manually or with the help of a program, referred to as assembler that reads each and every mnemonics instruction converts it into equivalent binary form and then moves on to read the next instruction and so on till the end of the program. Thus obtained program can be fed to the microprocessor for its execution.

High-level languages

These languages are more close to the spoken languages and are more understandable to the programmer. Here more than one instruction may be used for execution of a single machine level instruction. Like low level languages it also has to be, first, converted into an equivalent binary code for its execution by the microprocessor which is done by programs just like the assembler does in case of low level language. There are two types of such conversion programs:
1. Interpreter
2. Compiler

The program written in high-level language is called source code while its equivalent conversion into machine language is called object code which is finally executed. Both interpreter and compiler convert source code into object code.
Interpreter reads, converts and executes each instruction of source code before heading to the next one i.e. it first reads one instruction converts into binary form, executes it and then moves on towards the next one.
Compiler first reads and converts the whole soured code into object code and then executes this object code at ounces, as a whole.

Memory allocation and addressing

In any system all the peripherals are identified by an address location which occurs in binary form. The number of lines in address bus of a chip determines maximum possible memory locations that can be accessed by the chip (microprocessor). Taking an example of microprocessor 8085 it has 16 address lines i.e. each address will have 16 bits so maximum possible address locations are 2 to the power 16= 65,536. It means 64k byte of memory can be handled by it.
Now in order to retrieve a data stored at a memory location A2001H the microprocessor first put the address A2001H on the address bus which is sent to the memory module. In memory data is stored like in a notebook i.e. the first two digits (A2) of location address tells the address of a particular page number while remaining two digits (01) refers to line number at that page. Microprocessor sends an RD signal to memory modules which puts the data stored at that location in data but which is received by the microprocessor and data is retrieved in it.

History of microprocessors

Intel 4004 was the first microprocessor that was introduced in 1971, it was a 4 bit PMOS microprocessor used for small applications. 4004 and its improved 4 bit versions i.e. 4040 were used for following applications:
• Industrial control application
• Calculation instrumentation
• Commercial applications
• Videogames
• Toys etc.

The first 8 bit microprocessor was introduced in 1972 by Intel it was also based on PMOS technology. But it had some disadvantages like slow speed and incompatibility with TTL logic due to PMOS technology used in it. These limitations leaded introduction of a new more powerful and faster microprocessor Intel 8080 but it also had a drawback that it was operated upon three power supplies to eliminate it an another chip was introduced i.e. 8085 in 1975 which was operated upon only a single power supply of 5V and it used NMOS technology. 8080 is still used in some places like laboratories for the purpose of teaching the functioning of a basic microprocessor. Some other 8 bit microprocessors developed by other companies are:
Zilog's
• Z800
• Z80
Motorola's
• MC 6800
• MC 6809

These 8 bit microprocessors were very useful in industrial and other control applications some of them are:
• Instrumentation industry applications
• Small general purpose computers

These have memory addressing capability of 64K and clock frequency in range of 1-6 MHz using LSI technology. Now many 16 bit and 32 bit microprocessors are also preset there in the market from many deferent new companies which are capable of addressing a large memory and can work at higher clock frequencies.

What is a site with “WW38” instead of “WWW” and how to register

Can you imagine a website without the common hypertext www? “ww38.abc.com” instead of “www.abc.com”, Is it possible? Pretty stunned, right? What you heard right now is one hundred percent true. It is possible to have ‘ww38’ as a hypertext before the domain address of a website, instead of ‘www’. Today I am here to share you all the information that I have about this topic. Come along with me and we will have a deep research into the hypertext ‘ww38’ which can even break down the common rule of using hypertext.

Why we use www as prefix to every domain address?

As we all know about the hypertext ‘www’ which we use before every website. You may know the reason for providing this particular hypertext before every website and you might also even familiar with the full form of ‘www’. But for those who are unfamiliar with the term ‘www’, let me brief it before you: www is an abbreviation of ‘World Wide Web’, it is also known as ‘the Web’ in common. www is a hypertext used for interlinking hypertext documents and to access it through the internet. This method of hyperlinking documents of useful information to access via internet, was earlier proposed by Robert Cailliau in 1990. Today almost all the domain names use www as a prefix to their domain address. This act by the domains is due to the naming practice of internet hosts that these sites have been following for a long time. But we rarely type www as prefix to the sites, when we type the name of the website in the address bar, this is because today almost all the browser will capture the given address by adding the prefix ‘www’ automatically.

Sites with ‘ww38’ instead of ‘www’.

Did you now got the reason why we use www as a hypertext and prefix to many of the domain address? Now let us move into the new concept of ww38, shall we?

Very recently I found out that there can be domain names or addresses with ‘ww38’ as their prefixes. Few days back I was surfing my browser as regular, but in between my process, I was accidently I was redirected to a site with ww38 as its prefix. The site was ww38.kates-part.com, I was very much confused and even scared, as it would be any virus or any other type of malwares or even some sort of scam. I shutdown my browser as soon as I saw that hypertext and I was surprised to know it was not at a malware or any type of virus and it is really an internet site with prefix ‘ww38’. I was looking all over the internet for the info about this kind of prefix, and finally I came to know that there are many websites over the internet which accept ww38 as prefix.

What does ww38 means?

Providing ‘ww38’ as prefix to many of the sites over the internet means that, you can access or you are accessing ‘ww38’ named machine(server) from the main domain. ww38 or any similar other prefixes are only used to notify the server name or server number of the main website, that is being added after this prefix. As ‘www’ is the standard and commonly provided prefix, which is being followed for a long era of time, there is no rules to strictly follow on it.

While a web address is considered, the prefix can be anything which the developer of the website wishes, but the end part(eg: .co, .in, .com etc) should follow either of the valid format.

Now you might have understood the difference between ‘www’ and ‘ww38’, check yourself by providing ‘ww38’ instead of ‘www’ on your search field and it will surely accept it.

Engineering instruments for analysis of signals or waves

Overview of signal analyser

In various electrical and electronic instruments it is required to analyse the signal produced by them, there are numerous devices serving the purpose depending upon the signal they deal with. Some of them can be listed as:

• Signal analyser
• Distortion analysers
• Spectrum analyser
• Audio analyser
• Modulation analyse

These all analysing instruments may use different technique but do the same basic functioning of measuring the basic frequency of the signal the virtue of their analysis. For example in case of an spectrum analyser the signal frequency band is swept and the output is displaces by it in form of a graph between amplitude and frequency and it is capable of working in a frequency range of 0.002Hz to 250 GHz which is a very wide frequency range. On the other hand when we talk about an wave analyser is can be considered to be a voltmeter with the capability of taking measurement of the voltage of only a particular frequency in a collection of signals of different frequencies i.e. from a frequency band it measures the amplitude of one frequency and discards all other with the help of band pass filter circuits. It working frequency range is 10 Hz to 40 MHz we can take distortion analyser as another example of signal analyser which is used for measurement of the strength energy of the signal ling outside of a given frequency band. It is basically tells how much energy is present there in the signal which is not being taken under used that is why it's given the name distortion analyser. The working range of standard distortion analyser is from 5 Hz to 1MHz. An audio analyser can be studied as an extension of distortion analyser because is performs in the same way as a distortion analyser with an added quality of measuring the noise present in the original signal.

In order to study a more sophisticated and advanced analyser se can take modulation analyser which performs the function of recovering the whole envelope by tuning to a required signal. Here the modulation may:
• Amplitude modulation
• Frequency modulation
• Phase modulation

Each of the above analysers can have different form and type according to the complexity of their working and designing. So in order to have a insight of these device we need to explain each one of them separately.

Wave analysers

Here first thing, very important to understand, is that

What is wave form analysis?
The analysis of a waveform consists of measurement/determination of the basic parameters regarding an electrical harmonic signal which are:
1. Amplitude
2. Frequency
3. Phase angle

Here, it is well known that any periodic waveform can be thought to be a combination of two distinct parts that construct the whole waveform as their summation.
• A DC component and
• Series of sinusoidal harmonics

Analysis of these parameters can be carried out with the help of graphical of mathematical means (i.e. manually) but this all stuff becomes very tedious and also reduces the accuracy of the output, so in order to make it practically feasible we take electrical means under use. The most important section is band pass filter which actually filters out different components and leaves them for their individual analysis i.e. a very narrow band of frequencies is obtained from the output of the filter while all the other are attenuated to such a extent that only a requires portion remains remarkable.

Usually there is collection of signals in which each one is required to be measured separately that requires selection of required one from the cluster. According to this statement we can have a proper definition of a wave analyser as

"An instrument that as a frequency selective voltmeter tuned to the frequency of one desired signal and rejecting all other frequencies".

In actual practice the instrument comes with a dial fixed upon it which can be at any position to select a particular frequency this dial is generally referred to as frequency calibrated dial and thus produces signal can be displayed with help of a suitable display device such as voltmeter or CRO.

The frequency to be dealt with decides the type of wave analyser i.e. depending upon the frequency there are two types of wave analysers
1. Frequency selective
2. Heterodyne wave analyser 

Frequency selective wave analyser

When it is requires dealing with the frequency in audio range, the analyser, in this case, is referred to as frequency selective wave analyser.
Here analysis is performed in several different steps such that the output of one stage is fed to the input of next one. In this way in order to study functioning and interconnection of each stage we will be discussing them separately.

1. Attenuator: Firstly, the input signal is fed to the input attenuator in order to bring the signal strength within measurable range, in case it's caring larger energy than required. The attenuator is set by the range switch mounted upon the front panel of the instruments which provides the external control to the input signal strength.

2. Driver amplifier: Thus attenuated signal may or may not be of a specific required strength and form so. To meet the requirement this attenuated signal also has to be amplified that is performed by the driver amplifier.

3. High Q-active filter: This section is employed with the purpose of selection of the desired frequency from the complex waveform. It comprises of a cascaded arrangement of RC resonant sections and filter amplifiers. The capacitor used in RC band pass filters is generally of polystyrene capacitor type. And for tuning of the signal at a desired frequency, precision potentiometer is brought in use that proves to be very precise for frequency selection.

4. Final stage amplifier: The selected frequency signal is, now, supplied two stages i.e.
• Meter circuit
• Un-tuned buffer amplifier

Meter circuit involves amplifier that amplifies selected signal to s desired level so as to display it with the help of some display device and also calibrates it. While buffer amplifier involves a recorder or an electronic counter

It is also very important to emphasise that frequency selective analyser has a narrow band width which has typical value of about 1 % of selected frequency

Heterodyne wave analyser

This category of wave analysers works upon the signals in range of megahertz in which , again the input signal is applied to the device through an attenuator for the same purpose as in frequency selective wave analysers i.e. to bring the signal strength under control.

It also employs some certain steps while attenuation, amplification and filtration. After attenuation the signal is then passed to a amplifier stage that feeds the attenuated signal to the first mixture stage, also called local oscillator whose frequency is in order of the band pass filter of i.f. amplifier that is the next section of the system which gets the output from mixture ,furthermore frequency of local oscillator is adjustable . i.f. amplifier than feeds to the next mixture that mixes the signal to a crystal controlled oscillator such its frequency is so adjusted to produce an output of frequency centered at zero frequency.

A controllable band width active filter is employed in the next section that allows a selected frequency component to pass to the meter circuit.

Here it is to be noticed that the whole system works upon mixing of the original signal which other frequencies having frequency in range of megahertz. The accuracy of the whole system can be improved by introduction of devices capable of producing the frequency accurately. Frequency synchronizers and automatic frequency control having higher resolution and good accuracy, serves the purpose well. Where automatic frequency control (AFC) makes the system to get attached with the signal frequency and avoids the possibility of drifting between them.

Applications of wave analyzer

Wave analyser being capable of performing analysis upon gives complex waveform it proves to be applicable in a number of measurement systems like:
• Electrical measurement
• Sound measurement
• Vibration measurement

Industrially machines like motor rotors and cutters generate a large amount of noise due to vibrations produced in them, which is obviously an undesired output from them. In order to minimize them it is, first, needed to analyse their pattern with the help of suitable wave analyser.

Discrete frequency pattern and resonance related to the motion of the machine can be analysed swith the help of the wave analyser. After recognition of source of vibration and the way it is being produced an appropriate way can be obtained to eliminate that.

Harmonic distortion analyser

A sinusoidal waveform should be generated when a sinusoidal signal is applied to some electronic processing devices like an amplifier. But in most of the cases it is not seen to be with so perfection, the output does not comes out to be the exact copy of the one fed to its input i.e. some distortions always remains there at the output of the device. The components used in the electronic circuit may come out to exhibit non linear characteristics that become a reason of distortion in the output signal. Here, non linear characteristic refers to the behaviour of the component when it responds to the different external conditions differently e.g. a transistor has different gain factor at different frequencies that, definitely, leads to asymmetry when the input signal has a wide band width.

Harmonics are generated in the output signal due to this non-linearity of the components used, and thus, the distortion produced is called harmonic distortion.

Categories of distortions

Different devices and the components, used in it, become a source of distortion produced at the output waveform. But here, we will be discussing only those distortions that are generated by the amplifiers as amplifier are the most important part of any device and behaves in a different way with different frequencies. Some of the distortions produced by the amplifier circuits are as under:

Frequency distortion
As is discussed earlier, amplifier attains a different amplification factor for different frequencies. This non-linearity of the amplifier circuit results into frequency distortion.

Phase distortion
Some components like capacitors and inductors stores energy in form of electric field and magnetic fields respectively while their operation in circuit. These energy components leads to the shifting the output waveform by a specific angle with respect the input signal, this results into phase dissimilarity in output and input waveforms are generates phase distortion in the signal. It is to be emphasised that if phase shift is same in the entire signal i.e. if each components of the input waveforms is shifted by the same angle the resulting shift will not be remarkable. But generally it is seen that the shift does not come out to be same throughout the signal different frequency components have gains different phase shift leading to a noticeable distortion.

Amplitude distortion
Due to formation of the harmonics of the supplied signal by the amplifier of the device it leads to generation of the harmonic distortion in it. Harmonic in the signal always results into an amplitude distortion of the input signal. The best example to illustrate amplitude distortion is that when the amplifier is overdriven it leads to overshooting the operating point that results into clipping off a portion of the original waveform which is a type of amplitude distortion.

Intermediate distortion
The waveform, generally taken under analysis, occurs to be a complex waveform containing signals of more than one frequency thus coexistence of different frequencies leads to their interaction. As a result at the output some new signals are generated with frequency equal to sum and difference of the parental frequencies.

Cross-over distortion
This type of distortion is generally seen in push-pull amplifiers because of incorrect boas levels.

Total Harmonic distortion

For the purpose of studding total harmonic distortion of a given system we initially take the input to be in sine waveform. The input sine wave attains harmonics at the output due to non-linearity of the system such harmonics occurs with frequencies equal to a multiple of input signal. The total harmonic content of the wave comprises Total Harmonic Distortion (THD). Mathematically it is given by the square root of the sum of square of all the harmonics divided by the actual or fundamental signal.

Inter-modulation distortion

When two signals of different frequencies, one of high frequency while other one having low frequency, are mixed together it gives rise to only two frequencies at the output, in case of linear circuit. But the scenario changes when these frequencies are fed to an non-linear circuit as in this case four frequencies occurs at the output are
• Original high frequency
• Original low frequency
• Sum of original frequencies
• Difference of original frequencies
Many harmonics also occurs there along with their sum and difference.

Working of inter-modulation distortion analyzer

The system requires two different input frequencies which are made to fix. According to SMPTE (Society of Motion Picture and Television Engineers) these are taken as
f1= 7 kHz and
f2= 60 kHz
While there is standardization, DIN 45403, which set its own standard of frequencies as
f1=8 kHz and
f2=250 kHz

In both of cases the amplitude of frequencies is kept in ratio of 1:4 i.e. the signal of lesser frequency is made to have greater amplitude than that of higher frequency in order to expect a lower degree of non linearity. The mixture of these to frequencies is further fed to high pass filter whose outcome comprises of high frequency carrier and a low frequency modulation. The output thus obtain can be seen with help of an SRC.