Sampling

Question 1

What’s sampling?

Answer 1

The amplitude of a continuous analogue signal is measured at small time intervals and turned into a digital string of binary numbers, (sampling).
A sampled waveform is made from digital pulses and the original sample is reconstructed.

Question 2

What is quantisation error?

Answer 2

Bits per sample determine the number of quantisation levels. If it’s 3 bits per sample, N=2^3 gives 8 levels. For a sample, if the signal doesn’t match up with a level, the system records the nearest level to the signal. Increasing the number of quantisation levels makes a better match. Quantisation error is the difference between the signal value and the quantisation level.

Question 3

What’s resolution?

Answer 3

The resolution of a sample is the smallest change in potential difference that can be determined.
Resolution (V) = PD range of signal/no of quantisation levels.

Question 4

What considerations should be made for the number of levels?

Answer 4

Increasing the number of quantisation levels increases demands on data storage and transmission. Also, levels must be greater in size than the level of noise variation or else noise will be sampled to a great detail.

Question 5

What’s the formula for maximum number of useful levels?

Answer 5

Max number of useful levels = total signal variation/noise variation = Vtotal/Vnoise. N=2^b so 2^b=Vtotal/Vnoise

Question 6

What are advantages of digital over analogue recording?

Answer 6

Can be edited, easy storage, can be played on many devices.