Quote Originally Posted by gainesvillegreen
TDS is only the type of measurement and measures the same thing as does EC. TDS is indeed as accurate as EC, if not more so (considering it typically has more significant figures per readout). As long as you set the correct conversion ratio, TDS is fine.
Can't agree with you G. First of all, TDS, Total Dissolved Solids, is something no meter actually measures. Instead it uses EC, Electrical Conductivity, to guestimate for you what the TDS is based upon a theory that the TDS effects conductivity in water.

OK, next the TDS is actually just a factor of EC in microsiemens times 600 - 700. Each pen manufacturer uses a slightly different factor and some nute companies put out a different TDS chart per popular meter (Hanna, GH, etc...).

Took me a while to get my head around, but EC is the true reading (so to speak, as there are other factors) and TDS is kind of the educated guestimate.