# Difference between Digital and Analog signals

Discussion in 'Electronic Basics' started by karthik, May 31, 2006.

1. ### karthikGuest

What is the difference between the Digital signals and Analog signals
If anyone explain me pls

2. ### Noway2Guest

None, digital is a subset of analog.

here.

3. ### John PopelishGuest

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.

4. ### Dorian McIntireGuest

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

5. ### PuckdropperGuest

Sounds like homework to me.

Puckdropper

6. ### Noway2Guest

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.