Being a typical man, I don't as a rule "read directions". I too have a commercial Bluelab Truncheon and by golly, you're right. There it is in plain English, "CF".

I dunno!

I'm dropping a link to Bluelab's "Contact Us" from their Web page. They are very quick to respond to questions via email. I've contacted them on several occasions.

When you find out what the "CF" stands for, post it back here on the 4m so the rest of us can gain the knowledge too. Thanks.

Here is a link that might be useful: Bluelab's

CF = Conductivity Factor = The electrical conductivity of the nutrient solution. Goes up and down with it's concentration Good method of comparing nutrient strength.
Don't use "ppm", cause these meters convert CF into ppm by multiplying it with a "fiddle factor". Use CF!. You'll get used to it quickly.

CF = EC x 10
not really sure why there are both though. It can make things confusing.

Thanks for the response Fellas, Once again, Very Much Appreciated, Fred

Thanks guys, for posting/answering the question! I'm just getting into hydroponics and I'm completely new to the lingo.. but this was helpful!