Carbon dioxide in wine can be measured using a variety of analytical tech­niques and instruments, including the Carbo­doseur, titration, blood gas analyzers, and CO2-specific electrodes. The simplest method is the use of Carbodoseur.

Carbodoseur is a simple test that relies on physically agitating a wine sample to see how much CO2 is driven off by the process. Measuring the physical displacement, measuring the temperature, and correlating this on a graph will give a rough estimate of the amount of dissolved CO2 in a wine. It's probably accurate to within 10 %. What the makers of the chart probably did was use some sort of probe or intensely analytical test to determine the true dissolved CO2, and then correlated the displacement to this.

The Carbodoseur is a glass tube that measures the amount of CO2 outgassed from a fixed quantity of wine. Comparing this volume to a calibration chart, one can read directly in mg CO2/liter of wine sample. It is relatively easy to use and gives reproducible results. Since the Carbodoseur method doesn’t require the sample to be treated to facilitate “release” of CO2, results may be variable depending upon pH, temperature, etc.“