*** The conversion of continuous analog data to discrete digital data is called analog to digital conversion, or simply A/D conversion.
Typically, A/D conversion is performed either by hardware devices incorporated in the computer's input circuitry. All A/D conversion systems must have five steps -
(d) Conditioning, and
In fig (a) shows the temperature as recorded by an analog thermometer. In fig (b), these data have been converted to an electronic signal. The signal at this point is still too weak for the A/D converter to work with, so it is amplified Fig (c). This amplified signal is then conditioned to eliminate electronic noise in fig(d). Finally, the amplified analog signal is quantized and passed on to the computer fig(e).