Book Analog Interfacing to Embedded Microprocessors
light intensity, pressure, etc.) and not on a specific voltage range. In fact, our
0-to-100°C range might be converted to a 0-to-5 volt swing or a 0-to-1 volt
swing. In either case, the dynamic range that we have to measure is the same.
However, the 0-to-5V range uses 19.5 mV steps (5v/256) for 1°C accuracy and
4.8 mV steps (5v/1024) for .1°C accuracy. If we use a 0-to-1V swing, we have
step sizes of 3.9 mV and 976 mV. This affects the ADC choices, the selection of
opamps, and other considerations. These will be examined in more detail in
later chapters. The important point is that the dynamic range of the system
determines how many bits of precision are needed to measure or control
something; how that range is translated into analog and then into digital
values further constrains the design.
Calibration
Dynamic range brings with it calibration issues. A certain dynamic range
implies a certain number of bits of precision. But real parts that are used
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