Ppm question

I am making the leap to hydro but have a few q's about ppm's. I realize that there are different readings (EC, Hanna, Truncheon) but how do you know which one to use with feeding charts, I have not seen a reference to which format on any of the charts I have seen. I know EC is EC but when comparing hanna vs. truncheon it could be the difference between defficiencies and burn. Also if I am measuring my ppm and I want say 500 ppm and my water is say 50 ppm, do I discount my water? would I mix it to 450, 500 or 550? Thanks in advance. Does anyone else think it would be simpler to just do things in EC or is it just me?

Also here is a chart I found while doing a little research, shows the differences between the methods.

View attachment 1707361

i have the hanna intrument with all measuring tools.even temp.i ve been using the ppm feature .ive had my ppm all the way up to 1300 ppm.im doing mid pressure aeroponics

I run mine by the PPM's and I go to whatever number i want...ie if im looking for 500 i just add to 500 and dont minus the water

You shouldnt minus the water... the reason your water is giving you PPM's is because there are non organic chemical in the water, those actually do need to be considered when feeding.

any of the blue labs meter have the option of all three types so the best choice of meter is blue lab then the choice of
what way is up to you

blue lab is the way to go!

invest in something good. 5 year warranty.