Mike I have some Digitron formulas at home. I'll post them tonight.
As for an explanation of Digitron testing, John Copeland of Fox Valley Karts wrote the following excellent explanation:
With the introduction of the Digatron Fuel Meter, fuel checking went high tech. What the meter actually measures is called the "dielectric constant" of the sample. Some folks mistakenly think that the dielectric constant and conductivity are the same, but they are very different. Conductivity is the ability to pass an electric current between two electrodes and is measured as 1 /resistance with a direct current. Dielectric constant is a measure of capacitance measured with an alternating current. While both distilled water and iso?octane have very low conductance, the dielectric constant of distilled water is 80 and isooctane is 1.94!
Anyway, the Digatron meter measures the dielectric constant of the fuel sample. The national tech officials have specified that the meter be calibrated to ?55 with the probe immersed in cyclohexane, which has a dielectric constant of 2.023. After this calibration, the probe is immersed in the fuel sample and it may not read 0.0 or higher. Additives like alcohols, Propylene Oxide, or others tend to align themselves with an electric field (chemists say they're "polar") and they have higher dielectric constants. It only takes a drop or two of these rascals to make the meter read in the positive range and you're illegal. Setting the meter at ?55 gives you plenty of room for minor variations in gasoline composition or for different oils, but it will blow the whistle on most of the funny stuff.