Significant digits least count

All digits between the least and most significant are counted as significant digits. 

In the digital domain, these conversion gains can be reported as quantization step equivalents (QSE) these have units (for example) of counts per photon, counts per irradiance unit, or counts per ampere. A single count (a.k.a least significant bit or LSB) is called the step size and is usually reported as microvolts or millivolts per count. 

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