PPM and TDS are both EC times one of a several different "conversion" numbers(500,640,650,700,768 and a few more I can't remember). EC is EC. Period. If you haven't bought a meter yet, go with EC.
i use a combo of organic and chems i notice when i mix my nutes when i add some of the organic additives my ppms dont change at all. i dont know why but they dont move. that is why i think they said it wont work. i to would love to know why.
fb can u elaborate on this?
Don't buy Hanna, Ive replaced the same combo meter twice in one year and will be going elsewhere. I'm not the only one, many here have had the same problem, there junk. Karma, One Love
Water itself is something of an insulator. It's the stuff in the water that that allows Electrical Conductivity(EC, get it...heh heh). I don't do organics but, my guess would be that the ingredients in question are somehow non conductive. First I've heard this. Fascinating. (insert Spock smilie)
On another note, having blown over $300 on the great fan debacle of aught eight, I did much research on EC and pH meters and pens. For EC, the Bluelab EC Trucheon was the hands down favorite. For pH Milwaukee got the best marks followed by Oakton followed by Hanna. Me, I stuck with test drops from the aquarium store.
thanks fb i like my oaktron ph meter but everyone should keep test drops around to double check there meter they arent the most accurate but u get an idea and the are never off by much. changin batteries and not allowin the ph probe to dry out helps extend the life of ur meters and keeps em workin better longer.
Don't buy Hanna, Ive replaced the same combo meter twice in one year and will be going elsewhere. I'm not the only one, many here have had the same problem, there junk. Karma, One Love
by far the mostsuperior instrument ive used is the blue lab combo meter, i get them thru the kind canna collective for 175 instead of 300. its a steal of a deal, but still worth every penny without the medical discount.
organic nutes arent as "salty" as the chems are, so they coduct less electicity. a equation i use is (organic ppm = chem ppm x 1.25). so my organic nutes read 750 on the ppm metere and its equivilant to roughly 1000 ppm of chems. all organic nutes vary in ratio though, but are roughly on par unless its fulvic and humic acids which read vitrually nil.
ps the combo meter from bluelab has ppm, tds, and ec. peace, d