What does this equation mean?

Once the signal is a clean, conditioned voltage, it has to become a digital code, and that conversion is not free either. An analog-to-digital converter maps a continuous voltage onto one of 2^N discrete codes spaced by a quantization step $\Delta$ = $V_{FS}$/2^{N} , and that rounding itself injects noise, with power approximately $\Delta^2$/12 spread across the sampled bandwidth. The industry-standard way to describe and test this — offset error, gain error, integral and differential nonlinearity, effective number of bits — is defined by IEEE Standard 1241, which exists precisely so that a converter from one vendor can be compared against another using the same measured definitions rather than incompatible datasheet marketing language [ 12 ] . Many sensor front ends sidestep some quantization noise using oversampling: sampling far faster than the signal actually requires spreads the fixed quantization noise over a wider bandwidth, so that filtering back down to the signal band recovers roughly 10$\log_{10}(\text{OSR})$ decibels of signal-to-noise ratio for a plain oversampled converter, where OSR is the oversampling ratio — and considerably more once the converter also shapes that noise rather than merely spreading it. A 2018 sigma-delta ADC built for a digital MEMS vibration gyroscope demonstrates the payoff directly: a switched-capacitor design achieving 107.6 dB of dynamic range and 100.2 dB signal-to-noise ratio across a 2 kHz measurement bandwidth, at 3.2 milliwatts, specifically by using oversampling with noise shaping rather than a faster, dumber converter [ 11 ] .