Avinash,
Perhaps you are mixing metaphors.
http://en.wikipedia.org/wiki/War_of_Currents
"Direct Current" refers to the unidirectional flow of electric charge, while "Alternating Current" refers to the flow of charge that periodically reverses direction.
An "Analog Signal" refers to a continuous signal for which a time varying feature (such as signal amplitude) is a representation of some other varying quantity (analogous to another time varying signal).
A "Digital Signal" is a representation of a sequence of discrete values of a digitized (encoded) Analog Signal.
So if I understand your question, Yes. The information communicated by a "Digital Signal" is carried by an analog signal.
Is that what you are asking?
Interesting thoughts... In my opinion, if we think of DC ("direct current") as of a "constant current" (e.g., power supply) then DC is not a signal...
Cyril,
The characteristic that makes DC current "Direct" Current is that it flow only in a single direction, not that it doesn't vary. A circuit that contains a thermistor who's resistance changes with temperature makes a great circuit for measuring temperature and is a DC circuit...
Is DC a signal?
That means:
We have to answer the question if a DC current (or voltage) carries any information.
My answer: Yes and No (it depends).
a) If DC is used to power any device (or something similar) it certainly is NOT a signal
b) However, if the EXISTENCE of DC (at a certain time) carries an information like on/off it can be considered - I think - as a signal.
Avinash,
It is coincidence that we have two pairs of concepts that begin with the same letters in the English Alphabet:
AC - Alternating Current
DC - Direct Current
A - Analog Signal
D - Digital Signal
AC/DC Converter - A circuit that transforms the bi-directional flow of current produced by a rotating wire generator into the uni-directional flow of current similar to that produced by a battery.
ADC - Analog-to-Digital Converter - A device that transforms a continuous energy characteristic (such as voltage or current) into a discrete symbolic pattern that has been encoded to represent information.
"AC" is often generalized to refer to any periodically varying characteristic (such as a voltage value with an amplitude that is modulated to follow the time profile of a sine wave). Strictly speaking, this is a mixture of terms, as AC refers to "current" not "voltage", but I often use it that way as well. The industry also uses AC and DC when referring to signal filters, such as removing the offset of a sine wave-modulated voltage as a "DC" filter or removing the high-frequency variations of a voltage through the application of an "AC" filter.
To your original question: "Is DC an Analog signal?", I agree with Lutz -- it depends.
If a circuit is using unidirectional, non-time encoded current to communicate the value of a transducer, then YES - in this case it is acting as an Analog signal.
If a circuit is using unidirectional, non-time encoded current for reasons other than communication (such as providing power), then NO - it is not a signal, analog or digital.
"One Man's Noise is another Man's Signal"... The whole thing becomes Philosophy in short order... =]
William, even the consumed power can be a signal. For example, I remember how in 80's, in a Bulgarian TV show, we viewers voted to nominate our favorites in the show by turning on/off (YES/NO) a powerful consumer in our homes... which caused big troubles in the energy system and the trick was canceled:)
Another example is the clever "current sensing" idea in car alarm systems where if some consumer is switched on (e.g., some car door is opened and switches on the courtesy light), the alarm is activated...
Yes, DC constant voltage is also an analog signal with a certain amplitude and with a certain frequency that is zero in this case. This could be any arbitrary constant voltage. So, a signal which has certain amplitude and frequency can be called an analog signal also.
It is interesting to see a young man who has a philosophy of phenomena in this world:)
BTW it is possible to have an alternating voltage with a constant current. For example, connect a DC current source to an AC voltage source and you will see that the voltage will periodically change its polarity while the current direction will stay constant.
I think the answer lies in the terms used in the question itself. "Analog" signal, by standard acceptable definitions which are those signals which are continuous with respect to both time and the parameter of measurement of the signal, like voltage, temperature, current etc. A "DC" is one which has a fixed direction of flow and a consistent value at any time T. Therefore it is very clear that YES, a dc signal is an analog signal as long as it is continuous in form. Please let me know what you think!
According to Lutz's "b" above, I would say that DC (voltage, current) can carry 1 bit information (e.g., presence = 1, absence = 0).
Dear Avinash Kumar sir,
Agreed with Cyril Mechkov and Luciano da F. Costa sir and rest of the answers, I would like to add my point too.
DC is a 100% analog signal (I am assuming that you wanted to ask if a constant voltage is a analog or digital signal). Also a constant signal is only the signal that is periodic in nature but its period is not defined.
Analog signal : Continuous in x and y domain
Digital signal : Discrete in x and y domain
Analog Signal -> Sampling -> Quantization -> Digital Signal
Rest depends upon our perception and usage.
Yes , a DC is a signal with no change in the direction. It is always positive or negative. However, the amplitude may change significantly
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Physical Phenomena
- Luminescence
- Fluorescence