The resolution of commercial ADCs is specified in bits. In an ADC, the available resolution equals (2n)-1, where n is the number of bits. For example, an 8-bit converter provides a resolution of (28)-1, which equals 255. In this case, the full-scale input range of the converter divided by 255 will equal the smallest signal it can resolve. For example, an 8-bit ADC with a 5 V full-scale input range will have a limiting resolution of 19.6 mV.

In selecting an appropriate ADC to use, we need to find a device that has a resolution better than the measurement resolution but, for economy’s sake, not a great deal better.

Reproduced with the permission of Analog Devices, Inc.