Analog to Digital converters are used in the entire electronic world. Computer microprocessors only perform sophisticated processing on digitized signals. When a signal is in the digital form, it is less susceptible to the deleterious effects of additive noise. Analog to Digital Converters provides a link between the analog world of transducers and the digital world of signal processing and data handling. Analog to Digital converters are primarily applicable in all fields and areas where an analog signal needs to be processed, stored, or transported into a digital signal.
Some typical examples of Analog to Digital Converter usage are the digital voltmeters, thermocouples, cell phones, and digital oscilloscopes. Most microcontrollers use 8, 10, 12, or 16 Analog to Digital Convertors. Mathematical relationships are conveniently used to shows how the number of bits an Analog to Digital Converter handles determines its particular theoretical resolution: An n-bit Analog to Digital Converter has a resolution of one part in 2^n. For example, a 12-bit Analog to Digital Converter has a resolution of one part in 4,096, where 2^12= 4,096.
This means that a 12-bit Analog to Digital Convertor with a maximum input voltage of 10 VDC can resolve the measurement into 10VDC/4096. This amounts to 0.00244 VDC, equivalent to 2.44 mV. For the same range of 0 to 10 VDC, a 16-bit Analog to Digital Converter resolution is 10/216 amounting to 10/65,536. The figure is equivalent to 0.153mV. The resolution is usually specified with respect to the full-range reading of the ADC, and not with regards to the measured value at any particular instant (Sunter & Nagi, 1997).
A successive-approximation converter comprises a Digital to Analog Converter (DAC), a comparator (single), and registers and control logic. .When the analog voltage to be determined is available at the comparator’s input, the control system logic initially sets all the bits to zero. Then the Digital to Analog Convertor’s most significant bit, often abbreviated as MSB is set to 1, which forces the Digital to Analog Convertor output to half of full scale.