Hello Professor,
Can you explain the difference between EC and PPM testing meters? Is one better than another for measuring out my fertilizer, or does it really matter what system I use?
So and So,
Somewhere out There.
Hello So and So,
Let’s start with the definitions of each abbreviation. EC stands for Electrical Conductivity. An EC meter passes a current of electricity through the nutrient solution, and then the resistance of the current is calculated. EC is more commonly used in Europe than in the U.S.
PPM stands for Parts Per Million. Imagine having a bowl with a million molecules in it. The majority of the molecules are water, but mixed into the batch are four hundred assorted nutrient salt molecules which gives you have a four hundred parts per million, or 400 PPM. This is a very simple way of looking at it.
Here’s where things get a bit funny: the meters that measure PPM initially use EC to determine the resistance of those salts and then convert that number into PPM. To muddle things up a bit more PPM meters can be set to different measurement ratios (commonly 0.5 and 0.7).
If you had two meters set to the two different ratios and you tested the same batch of fertilizer mix you would get two different PPM numbers. When using a PPM meter it’s best to keep it calibrated the same way all the time and just use that one setting. That’s the easiest thing to do when you are only dealing with your own grow, but once you start talking to other growers and you don’t know what setting they have used, you could be discussing wildly different mixing ratios and get very confused with each other.
Whatever setting is used, PPM meters get the nutrient mix numbers in the ballpark and generally speaking, that’s good enough.
If I was being purely logical I would say go with the EC system. The meters cost more, but the numbers will be universal and not as open to silly mistakes. However, I cut my teeth with the PPM system and kept my meter faithfully set to 0.5. Which means that when I think of mixing nutrients I think in PPM, but that’s just me. Long story short: once you pick a system, try and stick to it. If you wind up hating it for some reason you could always switch to the other and see if it’s a better fit.
I hope this didn’t make things worse for you.
Professor Lee.
