problem wiv my ec reading ? help fellow growers lol

[BoomBoom82]

:thumbsup:i dont really understand the reading on my e.c meter. in normal water it reads 0.6. my plants r now on grow 18 on 6 off an my ec is 1.8 ? when it says 1.8i have taken in2 account the water already having 0.6 in dead salts etc. is this ec reading correct at 1.8 or does my meter have 2 read 12 if so that means i would use like the whole bottle a an the whole bottle b. any help an advice would b grateful thx:jointsmile:

[TheGreenFog]

I know very little about EC, but I do know about PPM, so I had to convert it.

Measuring PPM/EC/TDS

TDS is the measuring of the amount of salts in a solution. For alot of applications the amount of salt is indicitive of the levels of other stuff in a solution. TDS/PPM meters sold for gardening and aquariums figure the amount of salt in Parts Per Million by measuring the Electrical Conductivity of the solution under test. So a PPM/TDS meter is a EC meter that converts the EC value into PPM values. There are alot of descriptions online about why and how to measure PPM/TDS or EC so google for them if you want alot more details.

EC is a measure of Electrical Conductivity from two probes 1cm apart. 1 EC is = 1 microsiemens, to convert from EC to siemens multiply by 1E-6. EC can be converted to PPM by multiplying by 500. PPM can be converted to EC by dividing by 500. To convert from siemens to Ohms is s=1/ohms, you can also go the other way and do ohm=1/s for siemens to ohms. Siemens is also known as Mhos, which comes from ohm written backward.

The number 500 used to convert between PPM and EC is called the Conversion Factor. Different salts will have different conversion factors because some conduct better or worse than others. NaCl's is 500, this seems to be the most common standard used, and is what was used for the calibration solutions.

If EC/PPM is just measuring the Conductance (or resistance) then why not use a volt/ohm meter directly?? Because they pass DC current thru the probes and you cannot measure conductivity of salts with DC current because it will rip the molecules apart, and since the molecules are what conducts the electricity you get a constantly changing reading that is useless. Overcome this by using an AC signal. If the frequency is high enough (>1khz it seems) the molecules dont have time to move apart before they are pulled in the opposite direction. Sort of like how high DC current will throw a person off of it, where as AC forces them to hold on and get shocked to death or something.

FULL TEXT (http://www.octiva.net/projects/ppm/)


So, your water's original EC is 0.6, so that would mean it has a parts per million of 240ppm. So, then your EC after you add your nutrients is 1.2, meaning 480ppm. That is about half strength of what you would want for your vegetative state. Most people push the PPM higher than that, even as high as 1200 or so, but staying in the 600-800s is alright as well. Also, must take into account the ppm you already have in your water...

It shouldn't take the whole bottle. If it does, something is wrong. How much are you adding? What kind of nutes? How many weeks old are the plants? How many plants? :D

Be cool.


The Fog :rastasmoke:

[BoomBoom82]

ive got 40 plants from clones some r differnt strains and sizes as it was r first grow and we had no say in the clones we got. i am goin 2 grow my own mother from seed but 4 now am am using vitalink and vitalink bio pak. i have 2 x 90 litre nute tanks 2 :thumbsup:

[TheGreenFog]

well, with a res that large, you might very well have to use a whole bottle! :) It should have directions per gallon/per liter...so you should just be able to follow that. Never heard of that brand. What strains you have in your 40 girls?



The Fog :rastasmoke