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    I have seen in many, many cases that people design systems using ADCs with more bits than they really need. I have heard people say that they need a 16-bit ADC because they are using a 16-bit bus and also heard people say that they need a 24-bit ADC because they need as much accuracy as they can get. While there are indeed valid reasons for using an ADC with many more bits than might seem necessary, such as a wide signal dynamic range for example, the above reasons, and others, often lead to a more expensive, and possibly more complex, system than is required. In addition to the cost of the component itself, the component used may be physically larger so require a larger board area, there may be more traces to the component, there may be a requirement for additional circuitry requiring those components plus board area, etc. Here we try to assist the reader to a more prudent way to select ADC resolution. This is a revision of my original document posted last month (February 2017).