Computer Interfacing

Computer interfacing

Original analogue Re-constituted

signal analogue signal

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Time

Samples

Figure

3.3

Showing

the

type

of

error that occurs when

a

digitised analogue signal

is

reconstituted

series of digital samples of a sinewave are taken which,

when converted back, produce a corresponding series

of steps; this is the re-constituted analogue waveform. A

quite marked difference is evident between the original

and re-constituted waveforms. There is an amplitude fluc-

tuation now that was not present in the original signal;

this higher frequency variation is given the name,

quantisation noise.

Sample-and-hold circuits

The