This is the next step in the conversion process from analogue to digital. In this step, the sampled values from the first step are assigned to the nearest pre-defined values. In another words, the subdivision of the range of values of a variable into a finite number of non-overlapping, but not necessarily equal intervals. Each interval is represented by an assigned value.

This has an important reason, which is the limitation of the digital output device. For example if the output of the system is to convert analogue signals into 8 bit digital data, therefore there are 256 different data values (from 00000000 to 11111111) which must be assigned to the instantaneous input threshold. That means, there are not necessarily an exact output word of 8 bits for ANY input signal. Therefore we divide the whole space of the allowed analogue levels into the possible different values (here 256 possible values) and we try to compare the instantaneous input threshold to the nearest division point. If they overlap, that point is selected without hesitation. However if they do not overlap, that is, the input signal level either falls higher or lower, then we try to assign it to the nearest defined value. The worst case is when the sample value fall between two defined values. In this case, by prior agreement, the higher or lower value is selected. Afterwards, that selected value, which can be, in our example, any value from 0 to 255 is given it's digital equivalent.

In the following we have shown a simple 3-bit-system, which maps 1+1=2 volts into intervals of three bits.

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