General Advantages and Disadvantages...

"Real" engineers (at least this one) think you should do your own homework. I had to...

I believe his (or her) question WAS part of the homework. THIS engineer has learned many valuable lessons over 40 years of practice by asking other engineers for their opinions. Not all knowledge is in books (or on the internet).

Back to the poster's question.......As far as advantages of Analog vs Digital it depends on the task at hand. I am a little biased as I am an analog design engineer but analog is equivalent to "real time," while digital breaks up signals into discrete steps that can approach real time. Analog circuits can be complex (many components) to accomplish the design at hand especially if high precision is required or if control of EMI (Electro Magnetic Interference) is paramount. Digital circuits can replace analog functions and use less components (usually) but the digital components themselves may be highly complex devices and require programming. Digital circuits also tend to Generate EMI, often requiring analog components to lower the EMI emissions. EMI and EMC are big issues that affect all engineers today, including mechanical engineers that design electronic enclosures.

So analog does lots of good things and so does digital. Many designs today are a combination of both (a.k.a. Mixed Signal Design). Some digital designers predict that digital will eventually replace all analog design. I disagree. Some signals, such as physiological signals (heart beat, blood pressure, EKG, EEG, etc.) start out as minuscule analog signals and must be amplified and conditioned with analog circuitry before the A-D converter can process them.

I once saw two pictures that represented the difference between analog and digital, in an exaggerated way. The subject was a rose. The digital representation of the rose used many pixels, just like any printer or display would, except the pixels were visable. The analog picture of the rose was a continuous flowing and blending of colors with no visable boundries. Both pictures were printed and thus both made up of pixels, but the idea presented was that analog was a continuous, real time, representation while the digital was a discrete piecewise representation.

Analog will never effectively replace a digital computer, and digital will never replace amplification and signal conditioning of 10 microvolt EEG signals. As I said in the beginning, using analog or digital depends on the task at hand.
Good luck in your Engineering studies.

Congrat's on a great answer. Always good to see analog brains still around.

Oh, get over yourself already, the kid asked for your ideas and experience. Not the answer. This is for the guy that didn't give an answer.

Being new in the field, it is desirable to first know the basics from the text books and internet.

After this,you are surely benefited by the "real" engineers,who can clarify your doubts,from their knowledge gained from 'practical' experience.

Really guys! I hardly think that something so fundamental as analog vs digital--which has been around so very long now--is, or should be, the sole purview of engineers; especially considering that untold numbers of "untutored"--even those of pre-secondary-school age--have a fairly good grasp of the matter. To take a supercilious attitude also seems counterintuitive (in the U.S. at least) when one considers the increasing difficulty of recruiting, or retaining, young replacements to the engineering fields. (Should one wonder why?) And, certainly, no one could conceivably lose some competitive advantage responding to such a question as the thread starter asked. Plus, one of the basic lessons to be absorbed in early undergraduate work is the realization that, to be educated, one must increasingly motivate and educate one's self. Is a self-motivated (and a well and civily) spoken person who takes initiative to gain understanding from others who've gone before in his chosen occupation to be reproved for doing just that? Finally, one would do well to remember that "analog vs digital" is itself something that came second hand to the engineering fields. So if engineers stand on the shoulders of scientists, mathematicians,...etc. who came before, why then should a young developing engineer not look to more experienced engineers?

Thank you for the answers and opions.

it dosent matter to me whether or not im given a answer or opion or the debate, what im looking for is proof to my studies. ive found a lot of internet sites already that cover this issue, but a lot of it is written in such complex english, I cannot hope to understand the material (Ive only been doing this corse for a little over a week, and only with a basic understanding of electronics which I learned over 7 years ago in secondary school)

AnalogJim Thank you for your personal answer, and to the other person who said "do not give the definate answer" I will not be coping anything im given as my university are very strict with refrencing rules, and I would not be surprised to find that the members of the staff there, do not keep a eye on this and other sites.

Again Thank you.

Live long and Prosper!

Well, I think Analog Jim has stated it clearly, but as he said, he is a little bit biased toward analog devices. On behalf of the future engineer who asked the question, let me make several comments, I ask your indulgence if I put these paragraphs in basic terms, in sake for simplicity:

I have worked for over 30 years in the control field, and back on those good old days everything was analog in nature, since then what I have witnessed is the great marriage between the three big C's (CONTROL-COMMUNICATIONS-COMPUTATION), and this collaborating effort is driving up technology until our present days

The point is that, when computation began to work into control devices, also began the need for DIGITAL devices like A/D or D/A converters, in order to have data adcquisition systems that communicate computer or processors with the "real world" (because computers by their inherent nature, understand only digital signals)

If I should outline the advantages for DIGITAL devices or processisg, I must say:

- Flexibility, you can change completly the function of a system, just by software (changing the program), if you have it analog, you must change complete devices (hardware), or cabling

- Noise Rejection, as you only have to distinguish between two different basic levels (0 and 1), it is more easy to reject noisy signals, on contrast in an analog signal where you have an unlimited set of very near values, it is far complicated to separate the signal from the noise (this is why you have better quality in digital sound and video, than their analog counterparts)

- Communications capability, digital devices WERE BORN with communications capability, and have a lot of standards (defining communications media, like RS232, USB, RF, optical fiber, UTP Twisted Pair, Coaxial Cable, etc), and many protocols (rules for the messages, like: (Ethernet, TCP/IP, ModBus, FieldBus, etc), on contrast analog ones require analog signals to communicate like 4-20 mA (electric current), +/- 10 V (electric voltage), 3-15 PSI (pressure), these analog signals can not EASILY be bonded into a network like the digital ones

- Recording and memory, it a simple matter to record a digital signal, in fact digital processors use memory for several tasks: 1. Keep the program they execute, 2. Store the data or process pararmeters, for system configuration 3. Recognize codes, in order the distinguish between a letter, a data, a memory location, a stack pointer; moreover, digital compression makes possible to store a huge quantity of information in compact packets. When the instrumentation was analog the only way to record analog signals was using graphical recorders, but these registers could not be processed in order to determine: trends, produced quantities. maintenance records, etc for pruduction management

- Processing, digital signals are processed easily, and in various ways; filtering, conditioning, amplifying, coding, decoding, multiplexing; analog signals must be converted to digital before they can be processed

The advantages for ANALOG signals or devices are:

- Direct copuling with the "real world", you dónt need Data Adquisition Systems

- Immune to informatic viruses

- Robust, analog devices can stand mechanical and electric stresses which could destroy or impair digital ones; in fact, several protecting devices like snubbers and chokes are analog, and protect digital appliances

- Parallel fast processing, a digital controller must do many things on the same time, so it uses time multiplexing (that is, divides processing time between all tasks) to cope with this, on the other hand, if you have to do several tasks with analog devices, you just dedicate one device to each task, and they all work simultaneously, an this leads to fast processing when you have many signals, that may go beyond the capacity of the digital processor. In other words, if you increment ten times the number of signals, the speed of the digital processing will be less, but the analog processing speed will be the same (it will take the same time, because you add ten times more devices)

Interesting enough, our brain works both ANALOG and DIGITal, because it seems that our left hemisphere is better for spatial activities like motion (ANALOG functions), and the right is better for logic and language (DIGITAL functions)

Hope this help

Carlos