I have the truncheon also, it's great. The problem actually is with the ppm scales, how do you know which scale is being quoted when they tell you what the ppms should be. Therefore I don't pay any attention to ppm, I use a guide list that tells me the recomended CF or EC that way there is no confusion. They are also easier numbers to write down if you are keeping logs or notes.

The ppm scales are really only guesses anyway.

I know this probably doesn't really answer your question but most ppm lists I have seen also give either cf or ec so hopefully you can find some references to help you.

Thanks for the suggestion. I was looking in a tomato hydro book and it had the ec range for tomatos at 2 to 3.6 so that will most certainly work out better.

Phil in Alaska