Reliable ppm chart for marijuana??

I would say, test your testing equipment.

 

fwiw i had been using oakton tds meters for decades and finally got around to calling them to get a definitive answer on what factor they use. they say every oakton meter that has ever been is 0.5 scale. i couldnt find that published in any of their literature

 

Its ftom the box calibratet... i have turbo high hard tap water..

 

Again, I would say test your equipment, as they sometimes come DOA and miss-calibrated.

 

I hear what you saying tho..

 

I'm gonna add somethinh others seem not to have. Different brands of nutrients will have different appropriate ppms especially depending on what your using. I'm running seedlings at 700 right now BUT this is because I use an assload of beneficial microbes, and enzymes to prevent slime.(I run aeroponics) plus some sugar to feed to microbes.
With this I'm actually using less than 1/4 strength base nutes and 3/4 strength rapid start, and 1/8 strength cal mag(you always need at least a bit of cal mag if you use an RO system)

Also if you have a ro system remember to sterilize it regularly. Theres quite a bit of data proving virus's and bacteria build up in filters; in tests where people drank ro water vs. tap water more people drinking ro water ended up with nasty gastrointestinal diseases

 

Hey Santos , Its my understanding the .05 scale is used in North America with the .07 used in the Eu ?

 

Try this, it works for me.
http://www.lenntech.com/calculators/conductivity/tds-engels.htm