Quote Originally Posted by herbie the love bud
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.
Yep, you are right about that, but EC meters do generally give you an approximate TDS reading within 10% accuracy, although that's not great, it's the best your gonna get unless you do gravimetric analysis. But I go by EC myself anyways.
theghettorun Reviewed by theghettorun on . I need a cheap TDS meter The tds meter i got with my hydro set, dosent seem accurate at all, dose anyone have any suggestions on meters they've worked with and work good for under $50? Rating: 5