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What Is an ADC Reading?

ADC is an abbreviation for "analog-to-digital converter" and refers to a device that converts a fluctuating analog input signal̵2;typically a voltage signal̵2;into a series of discrete digital output signals, represented by the digits 1 and 0. An ADC reading is a reading on a meter, monitor or chart that represents the output signals not in binary, or base two, notation, but in decimal, or base ten, notation.

Resolution
- The accuracy, or resolution, of an ADC reading depends largely on the number of binary digits, or ̶0;bits," used to represent the decimal number. However, as the input voltage increases an ADC maintains a constant output voltage until it reaches the so-called "transition region," at which point the voltage jumps to the next level. In other words, a decimal ADC reading represents one in a series of discrete steps, or jumps, and so provides only an approximation of the real analog voltage at any time.
Errors
- Manufacturers typically quote the resolution of an ADC over the full range of voltages that it is capable of reading, rather for than any instantaneous reading. Furthermore, the quoted resolution is often higher than the real resolution because of a variety of errors that can occur. One such error, known as a missing code, occurs when an ADC cannot produce an accurate reading for a specific analog input. If you̵7;re choosing an ADC, you should always choose one that has more bits available than you actually need.
Electrical Noise
- Paradoxically, because of the way the output signal from an ADC is mathematically averaged, a ̶0;noisy̶1; input signal̵2;an input signal that suffers from electrical interference̵2;can often produce a more accurate ADC reading than an input signal that is completely noise-free. In fact, some ADC systems deliberately introduce a random noise signal̵2;known as ̶0;dither̶1;̵2;to the input signal to increase the accuracy and stability of the reading.
Calibration
- The accuracy of an ADC may decrease over time, especially in extreme operating temperatures, and most models need to be recalibrated every six to 12 months. You can perform recalibration with hardware, software or both. In any case, recalibration involves adjusting the gain and offset of the ADC to achieve the desired relationship between the input and output signals. "Gain" is the term used to describe the ratio between the output and input signals of the ADC, while "offset" describes the deviation of the ADC from the ̶0;ideal̶1; straight-line graph when the input voltage is zero.

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