TDS EC, PPM conversions, feeding routines help

Sarge

Sarge

Hey all,
I seem to be starting alot of topics as I always need to know something new which isn't always available or in language I can understand!
 
I bought an el cheapo TDS pen off eBay. It reads in PPM. Now I've read there are different conversion methods and that EC is standard but ppm can range depending on conversion. Is there a way to ID what type of TDS PPM unit I have? http://www.ebay.com.au/itm/Digital-LCD-TDS-PPM-Meter-Tester-Filter-Pen-Stick-Water-Quality-Purity-Aquarium-/121233107734?pt=AU_Seed_Starting_Hydroponics&hash=item1c3a0e6b16
 
That's the pen I have, cheapest piece off eBay. I tried emailing them all I get back is some illiterate message saying they have no idea.
 
The next thing is when people talk about giving their plants say 300ppms. To which scale? if someone is using one conversion method giving 300ppm, thats an ec of .6 but a EUtech conversion of 384 and a truncheon converson of 420.
 
Are target PPM's inclusive of base water PPMs or exclusive?
 
Ive looked at things like the lucas formula and it is hard coded numbers @ 8ml of micro to 3.78 litres of water and 16ml of bloom to 3.78l of water. Can this just be scaled down? My res is 13L, thats 27 and 55ml of nutes which is HUGE compared to the 4.7ml of nutes I'm using at the moment.
 
For a small seedling, less than 1ft tall, can the cycle be left longer than two weeks if the ppms are close to original range?
 
Does anybody else have any feeding routines they can share? Originally I was just going to go off the suggested amount on the bottle of flora bloom and micro with a correction to 0.75 but conflicting information ion numerous sources suggests raising the nutes a little, say by 40ppm every week to encourage growth, although I'm not sure if thats how it works.
 
I can't afford to spend $50 on a ppm pen. Would my best option be to buy another cheap tds pen but one which reads EC? Again though I will be in square one as to suggestions from others recommending target ppm's. Unless they know which conversion rating they're using, the quantity of nutrients will be wrong. To keep it simple, I am just using equal parts of micro and bloom at the moment and will up the bloom if the plant makes it to a blooming phase.
 
The basic relationship between PPM and EC is:
 
700PPM = 1 Mmho  (ms)
1400PPM = 2 Mmho  (ms)
2100PPM = 3 Mmho  (ms)
 
In North America PPM is commonly used and i know little about EC meters. I know you can buy meters that show both PPM and EC.
 
scratchzilla said:
I haven't used my ppm/EC meter in over a year. Just follow the instructions on the bottle.
Click to expand...
 
This is what I have been doing so far but checking ppm's after just because. With that said, do you increase doses every fortnight or do you maintain the exact same levels up until the plant starts blooming and fruiting or do you increase slowly then push the nutrients higher during bloom?
 
I follow the instructions to the letter. Depending on the plants stage, the bottle will say x amount for vegetative growth, and y amount for flowering.
 
I always go weaker than the instructions. With small plants, experience seems to help quite a bit with knowing how and when to feed. I find that every plant is different in its nutritional needs, and responding to the plant has always been how I have gone about my feeding schedule.
 
Hi Sarge,

I can't speak much to the meter and different scales because I'm still trying to figure it out myself. As I understand it the measurements are inclusive of the original ppm in the water you are using (the plants will get the sun total of the water and nute)

I could be wrong, but I believe that the Lucas formula uses RO water which has a very low ppm. The nutes would then provide the required feed. I haven't used Lucas formula, but have found that the lower strength H3ad formula gives me crumpled leaves at 700ppm. Things started to correct themselves when I dropped my nutes to about 500ppm.

Neil
 
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