Analog-to-Digital Conversion Algorithm with a Single Slope

Converting analog to digital has been increasingly important since the dawn of the digital era. While many take analog-to-digital conversion at face value and do not question the means of conversion, there are actually dozens of conversion techniques employed by electrical engineers, each with their own advantages and disadvantages.
The particular methodology shown here is called single slope and is one of the simplest kinds of conversion. The analog-to-digital convertor attempts to convert the analog signal into digital bits in a two-step process. First, a linear voltage ramp is created by the analog-to-digital convertor and a clock begins its count. Then, when the voltage ramp rises above the signal, the clock's count is output as a digital interpretation of the signal; the voltage ramp is reset at 0 V, the clock count is reset to 0, and the process begins again. This works because it is a linear ramp, and so the voltage interpretation is linearly proportional to the time (meaning the horizontal aspect is linearly proportional to the vertical aspect), so by recording the time, we record a scaled interpretation of the voltage.
Using single slope is subject to two caveats, both evident in the Demonstration: (1) the algorithm cannot interpret negative signals (because it uses a positive slope), and (2) the linear voltage ramps sometimes overshoot the signal (because the ramp is only compared to the signal at the end of a discrete time step).


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[1] P. Horowitz and W. Hill, The Art of Electronics, Cambridge: Cambridge University Press, 1998.
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