Difference between Digital and Analog signals

None, digital is a subset of analog.

Same as with your other post, please try a search engine before asking here.

Digital implies quantized. The signal is expected to have 2 or more specific states that are clearly distinguishable from each other, and each state represents a numerical value (0 or 1, in the case of binary digital signals). For example, a TTL logic signals might be expected to be a voltage either between 0 and 0.8 volts (to represent a zero value) or between 2.4 and 5 volts (to represent a 1 value). Voltage between .8 and 2.4 is not clearly and reliably distinguishable as either value.

Analog signals are continuous over an operating range. For example, many industrial measurement and control signals are communicated as a

4 to 20 milliamp current through the signal path. 4 milliamps represents a zero or minimum signal, and 20 milliamps represents a full scale value. Any current between 4 and 20 milliamps represents a valid signal of some proportionate value between zero and full scale. There are no gray areas that are not valid signals in this range. The number of possible values this range can represent is limited only by the noise and resolution of the system.

Analog values are represented by ANALOGOUS quantities in other systems. In analog system we can uses continuously variable quantities such as, but not limited to: mechanical rotation, voltage, current, distance, etc to represent other quantities. Analog values are not limited to electronics. For instance the loudness of my car radio is proportional to the position of my volume control. The position of a fuel gauge is proportional to the level of voltage or current sent to my cars fuel gauge which is proportional to the level of fuel in my fuel tank. An analog voltmeter uses the angle of the meters needle to represent a particular voltage whereas a digital voltmeter uses discrete digits to represent this voltage. Analog values have the advantage of being continuously variable but tend to lack precision because smaller and smaller quantities begin getting lost in "noise". One example of this limit is that I cannot measure 1.000001 volts with an analog meter because my eye cannot see one millionth of a division assuming I even had such divisions on the meter scale.

Digital values are represented by DIGITS and change in discrete, or definite, amounts. In digital systems we use discrete quantities such as, but not limited to: incremental rotation (remember the old-style digital clocks with numbers printed on a rotating ring), incremental voltage (not limited to high and low), incremental current, incremental distance, voltage or no voltage, etc to represent digits and use the position of these digits to represent larger and larger numbers. Digital systems are not limited to electronics. These digits can be represented by beads on an abacus, fingers on a hand or patterns of binary 1's (+5v) and 0's (0v) in a computer. Digital systems lack the ability to be continuously variable (try reading a digital voltmeter while measuring a varying voltage) but we can obtain any level of precision we want in a digital system by adding more digits to the system. For instance, in general, a 32 bit computer is capable of much more precision than a 4 bit computer (I say "in general" because a 4 bit computer could be programmed to "act like" a 32 bit computer).

Hope this helps

Dorian

"Noway2" wrote in news:1149094270.992771.52050 @j55g2000cwa.googlegroups.com:

Sounds like homework to me.

Puckdropper

--
www.uncreativelabs.net

This time of year, I would guess that it is probably a final exam question. There have certainly been a number of newbies appearing asking very "text book like" questions recently. Often times these questions are poorly phrased and are requesting to "compare and contrast" or describe different concepts.

I can't say that I have a problem with helping a student by giving them a nudge in the right direction or providing clarification on a subject that they have clearly made an attempt to understand or discuss. I believe it does not benefit anybody to withold information from someone who is making an effort to learn and understand. On the other hand, I do have a problem, though, with all this "pls send me, please give me, please provide me" knowing damned well that they are going to take this information and copy it verbatim on their homework or test and probably get a much better grade than someone who actually attempted the work.

It is also annoying when it is obvious, like in the OP, that no attempt has been made to even consult with basic resources like search engines. Instead, they simply ask for a handout. Unfortunately, there appear to be enough people who are willing to give it to them rather than making them at least put forth a minimal effort.