Questions: Digital vs. Analog Signals

Question 1

A temperature sensor outputs a voltage proportional to temperature, smoothly varying from 0V to 5V. This is:

• A. A digital signal
• B. An analog signal
• C. A binary signal
• D. A power signal

Answer: (B)

The signal varies continuously and can take any value between 0V and 5V. This continuous variation makes it an analog signal. To process it digitally, it would need to be converted by an analog-to-digital converter (ADC).

Question 2

A digital signal can represent any value with perfect accuracy.

• T. True
• F. False

Answer: False

Digital signals have finite resolution. An 8-bit digital signal can only represent 256 discrete values. If the analog value falls between two digital levels, it is rounded to the nearest one -- this introduces a small error called quantization error. Higher bit depth reduces this error but never eliminates it completely.

Question 3

Why are digital signals more resistant to noise than analog signals?

Model answer: A digital signal only needs to be recognized as 'high' or 'low' -- noise that shifts the voltage slightly does not change the interpretation. An analog signal's exact voltage IS the information, so any noise directly corrupts the data. As long as noise does not push a digital signal past the threshold between high and low, the information is perfectly preserved.

This noise immunity is why digital communication has largely replaced analog. A digital signal can be transmitted over long distances, regenerated at relay points (restoring perfect high/low levels), and arrive identical to what was sent. An analog signal degrades with every meter of transmission as noise accumulates.