My Fluke 28II multimeter is a twenty-thousand count, 4½ digit instrument. This refers to my instrument’s resolution, but what does it mean? Well, the counts and digits are effectively two ways of saying the same thing, but both terminologies are in common use so it’s good to have a handle on both. I’ll tell you my personal preference and offer justification for it later. In this section let’s deal with the counts first.
To start with, it should be noted that the practical count figure is almost always one count less than the naming convention we use to refer to it. For example, in my case (for a Fluke 28II), the practical resolution of my instrument is 19,999 counts. That is what the instrument is actually capable of. However, when we refer to the counts by name we call this “twenty-thousand count”, and this is purely because a round number is easier to say! What we mean in practice is one less than that. The instrument specifications will usually quote you the practical counts as an actual figure, so with a well written specification there should be no ambiguity: