Figure 2. Noise floors (PSDs) for three digitizers in the Q4120 datalogger, using short-circuited (50-ohm) input recordings sampled with 100 samples/sec (top) and 20 samples/sec (bottom). The left axes represent the resolution (smallest input voltage that can be resolved) of the digitizer in decibels (relative to 1 V²/Hz), the right axes show the corresponding dynamic range of the system, which has a full-scale (peak to peak) input of 40 V. The horizontal, dashed lines show the resolution of the digitizer in bits, which follows from equation (7). Notice the effect of the FIR filters beyond 80% of the Nyquist frequency.