Embedded Systems Design, 2nd Edition

176 Embedded systems design

Quantisation errors

Careful examination of the combination chart reveals that

all is not well. Note the samples at time points 7 and 13. These

should be zero — however, the conversion process does not

convert them to zero but to a slightly higher value. The other

points show similar errors; this is the first type of error that the

conversion process can cause. These errors are known as

quantisation errors and are caused by the fact that the digital

representation is step based and consists of a selection from one of

a fixed number of values. The analogue signal has an infinite range

of values and the difference between the digital ...