An analog-to-digital converter (abbreviated ADC, A/D or A to D)
is a device that converts a continuous physical quantity
(usually voltage) to a digital number that represents the
quantity's amplitude. The conversion involves quantization of
the input, so it necessarily introduces a small amount of error.
The inverse operation is performed by a digital-to-analog
converter (DAC). Instead of doing a single conversion, an ADC
often performs the conversions ("samples" the input)
periodically. The result is a sequence of digital values that
have converted a continuous-time and continuous-amplitude analog
signal to a discrete-time and discrete-amplitude digital signal.
An ADC may also provide an isolated measurement such as an
electronic device that converts an input analog voltage or
current to a digital number proportional to the magnitude of the
voltage or current. However, some non-electronic or only
partially electronic devices, such as rotary encoders, can also
be considered ADCs. The digital output may use di