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You can think of acquiring data at such a small percentage of the full-scale range as an effective reduction in ADC resolution and we can describe this reduction mathematically, essentially working backward to determine the effective bit resolution of the ADC. (click to enlarge) So, what's the problem? the signal is "in the mud").įigure 3 - This is what the ADC sees as exposed by WinDaq's Show Dynamic Range function. The result is Figure 3 where the trace virtually disappears, meaning that the ADC doesn't have much signal to work with (i.e. Taking advantage of a cool WinDaq feature called Show Dynamic Range (see Figure 2), I can force the selected channel to automatically scale itself to fit between the upper and lower limits of the ADC's measurement range to provide a visual picture of what the ADC sees as it digitizes the channel's data.įigure 2 - Invoking WinDaq's Show Dynamic Range function tells the real story (click to enlarge.) In fact, this channel was acquired in a manner that we affectionately call "in the mud." The customer has vertically scaled the trace to provide only the illusion that all is well. Looks okay, right? Ah, but I have you at a disadvantage. The waveform was acquired with a 14-bit ADC. (click image to enlarge)įigure 1 is a screenshot of WinDaq-acquired data as viewed from WinDaq Playback software.

An example might help, and here's just one of many (the customer will forever remain nameless):įigure 1 - Channel data as typically viewed by the customer appears fine. The Fact, Folly and Mathematics of Analog to Digital Converter ResolutionĮveryone agrees that higher resolution analog to digital converters (ADCs) are better, right? So why do so many end-users shell out bucks for one and then fail to exploit that advantage? What I mean is that we are too often shocked when we receive data files from customers with data acquisition parameters set in a manner that throws ADC resolution under the bus.