The struggle lies in the fact that a TDS meter is a misnomer. They should be called TDIS or total dissolved IONIZABLE solids meter. It’s only a TDS meter if everything in solution is ionized.
In the lab we run a true TDS by drying a fixed amount of filtered solution and measuring the mass of the residue. Your sugars would show up in the residue.
The problem with a TDS “meter“ lies in the way that they make measurements. Your meter (likely) contains two probes. A tiny electrical current is applied across those probes. The ability of the solution to conduct that current is measured.
Water is a poor conductor of electricity. So the conductivity is low for pure water. Some substances, like nutrient salts, dissolve in water to create positively and negatively charged particles known as cations and anions.
These ions “complete the circuit” and allow electrical current to flow. The larger the number of ions, the larger the current. Meters are calibrated at the factory using reference standards of known strength.
Some substances, like sugar, dissolve in water without forming those charged particles. No charged particles, no electrical current. The particles are there, but the meter is incapable of detecting them.
I prepare 1 liter samples of each of my additives in individual containers. I delve out the highest concentration that I anticipate for the grow. I measure the ec of each and record the results. This gives me an idea of which ones to look out for when pushing ec limits.
Your question is a great one. I hope this puts your mind at ease. Here’s a little more information if you’re interested.
TDS
