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Hey Freak, please don't get angry with me, but I have to disagree with your statement about the EC of a hydro res all mixed up and ready to go as having no constituents, it is nothing but constituents mixed together to define the new compound solutions EC. Your statement is only true if you are looking at an individual element rather than a compound solution ie.. multiple components. Individual components are easy, N=0 EC, Potass=.139 10+6/cm mho, Phos=1.0E-17 10+6/cm mho and Distilled water is a liquid covalent compound which does not conduct electricity. If you drop one unit of each into a vat, the new substance EC would total a vector addition of the components ie..higher than the lowest and lower than the highest. This new solution would also have its own TDS in ppm. I think I threw you when I said "total EC/ppm" as I was trying to keep it short, but meant either total EC, or ppm of TDS, or any other measure for that matter like %/volume etc.
The closest I can math out currently is simply using the OEM stated N,P,K numbers on the products combined as they are indicated in %/wgt. This math can get very convoluted for just trying to answer my basic question of "How much of each do I have in this bin of distilled water?".
Using round numbers for example, I could say OK I'm mixing one ounce each 2,2,2 with an ounce 8,8,8 so should have a total of 10% of 2oz of N, P and K which I am then pouring into a 6 gal tub of distilled water. Now you have to convert gals of water to weight to get units the same for further math, so water is 8.345lbs per gal... unless its distilled which weighs slightly less missing some constituents, so we will say 8.337lbs per gallon x 6 gallon res x 16 (to get to ounces)=800.35 oz of water + 2oz of nutes=802.35oz x .10 (the 10% of 2 oz) Man thats enough to spin an old stoners head 20 times or so. I was just looking for something to stick into the tank and give me a reading, preferably digital.
It is possible to read the total solutions EC as the meters are certainly no more expensive than a Hanna Combo for TDS/Ph. Pulse, Amber Science and many others have models ranging from $70 on up to several hundred, depending on functions and they would still bump me into the same how much of N,P & K questions since we don't add individual elements, but compound elements. N we add for example is not just pure N, but a soluble compound of N2/N3 and others. Now we are saying that one of the constituents we are using is a compound itself..Arrrgh I don't want to do no more stinking math man. We had a unit in college way back when that measured N, but was specific to cow manure and everybody called it the "shitpot" or Shitbucket" I think. It was a couple of grand and used a reagent for a 5 minute long test. There are also units estimating N from Chlorophyll but they are specific to rice and corn I believe. HaHa, I think the basic answer to my question is just mix up whatever the OEM says to mix up for any given nute and assume he knows what he's talking about and didn't transpose any numbers somewhere along the line.
Finally near the end, but takes me to Racefan and his observations. Hey Race, I started wondering about all this stuff based on my real world mix I just finished fresh yesterday, so no extended runs as an intention. Real numbers on real nutes here, the Grow is 2-1-6, the Micro is 5-0-1 and the Bloom is 0-5-4 at one oz each into 6gal distilled per OEM to yield a 1000ppm. Now a total of 7-6-7 seemed low on N and high on K for a plant only 3 weeks into veg state, so I only wanted to try bumping the N a little if not also lowering the K using what I already own. So my question was simply "what do I put in there and how much do I put?". That led me into the math nightmare. HaHa, meanwhile I just mixed it up and put it back in service and dreamed about it all night.
You guys are going to hammer me aren't you? I know, I know get a life.. but I actually ponder this stuff and get pissed when I can't solve for correct answer. I'm still trying to figure out what I put in there and how much. Ok, fire away.