EC/TDS Meter?
- Thread starter slowmo77
- Start date
homebrewer
Well-Known Member
I use this one: http://www.sunlightsupply.com/p-12026-oakton-ecotestr-tds-low.aspx
It reads up to 1990 ppm and is on the 442 scale. Works great.
It reads up to 1990 ppm and is on the 442 scale. Works great.
homebrewer
Well-Known Member
PPM has a few different scales but they can all be directly converted to EC which is the same across the board. The meter I suggested is on the 442 scale and I feed my ak47 at about 950ppm or 1.3 EC during most of flower. That may seem light to some but again, ppm isn't the same unless you're on the same scale. Here is a look at the different scales and how they convert to one another:
http://www.hydroponics.net/learn/debate_over_ec_and_tds.asp
I prefer taking readings in PPM vs EC as the ppm scale is easier to work with when 'fine tuning' a feeding program that works for your strains and conditions.
slowmo77
Active Member
Thanks, im gonna be using the Fox Farm Trio pack and growing russian rocket fuel and easy ryder. i figure my best bet would be to just follow the feeding chart they provide and check the ppm based on the amount the chart says to use to figure what my ppm is. if that makes sense. the switch from soil to hydro isgonna be ruff i can already tell. lol
homebrewer
Well-Known Member
I would recommend against the feeding schedules on the backs of the bottles. Take one gallon of water, RO or tap, and take a ppm reading of said gallon. Add 5mls of fertilizer to it and take another reading of your water. Subtract the ppm of your base water, then divide by 5, this will give you an idea of how potent each ml of your fertilizer is. In hydro, I would not suggest feeding higher than 2.0 EC and would recommend you start flowering plants at about 1.3 EC. Less is more and the backs of the bottles error on the side of 'more'.
slowmo77
Active Member
lets see if ihave this right, the key is knowing which scale the tds meter is using. lets say my water before nutes is 100ppm then with nutes added it's 600ppm. minus the 100ppm of the plain water leaves me at 500ppm which would be 1.0ec assuming the tds meter is using the the lower scale. does that sound about right to you?
from what it sounds like i should get and EC meter rather than a TDS. i know that i'll only have to use it untill i get my system dialed in. i hope
from what it sounds like i should get and EC meter rather than a TDS. i know that i'll only have to use it untill i get my system dialed in. i hope
homebrewer
Well-Known Member
Your math is correct in figuring out the potency of your nutes, but not when it comes to feeding. If your water is 100ppm and you add 500ppm of nutes, you now have a 600ppm solution, the take-away being that you include your base water ppm when figuring total ppm. When I said my plants feed at 950 ppm, that includes my base water.
Now if you added 5mls of fertilzer to your 100ppm water resulting in 600ppm total, you know each ml of fertilizer into a gallon adds 100ppm. I use figures like this and plug them into an excel spreadsheet to determine how much bloom, grow, or whatever I need to add to get to the feeding levels that each of my strains like.
In regards to feeding, once you figure out what ppm/EC your plants like at different stages, the ppm meter is a little easier to use when mixing up nutes in your res. But again, when talking about feeding strength with people on the forum, EC is universal, ppm isn't.