It has been said many times on this forum that TDS meters do not measure ionic silver correctly, cannot measure silver nanoparticle concentration at all, and that they can only measure accurately the single substance they are calibrated for.
To illustrate this, I have made the following table as an example of the errors for common substances.
These are based on 1 gram of the substance per liter of water (1000 ppm) with the meter calibrated to table salt.
Compound | Conductivity uS | TDS Error |
NaCl | 1997 | 0 |
Na2CO3 | 1664 | -16.67% |
NaOH | 2168 | +8.6% |
NaHCO3 | 1069 | -53.5% |
TDS meters are actually conductivity meters with a simple mathematical conversion applied to their electrical conductivity measurement.
I was able to make this table because the conductivity of these substances is known. If the conductivity of silver oxide was actually known, then a conversion factor for silver could be made, but it is not known.