Following PPMs for under/overfeeding warnings

[JoeCollins]

Good luck finding the answer to your query. May the Canna spirits guide you.

It is an easy question to answer idk why you are so obstentantly refusing to do so. I can only assume you are here just to troll not to help.

 

[Death The Cultivator]

It is an easy question to answer idk why you are so obstentantly refusing to do so. I can only assume you are here just to troll not to help.

I've answered it. You aren't satisfied with the answer, may the Canna spirits guide you.

 

[JoeCollins]

I've answered it. You aren't satisfied with the answer, may the Canna spirits guide you.

I wasn't satisfied with your answer I was asking for clarification and you went off in the weeds. I am simply trying to ask about your reading of the numbers on the meter device, you are trying to tell me everything BUT what I am asking.

 

[Mañ'O'Green]

@JoeCollins
So I am trying to figure out a threshold for differentiating meter drift vs plant indications when measuring PPMs the following days after refilling my reservoir.

Buy a better meter if you are getting drift. The technical specifications for the Blue Lab meter I run are here: I get no drift beyond the meters capability from the factory. My meter can be off by +/- 50 PPM but it will be off by that same PPM all of the time. It does not drift around. It becomes obvious when it will not calibrate it is time to replace it.

Everything on the subject always says that if your PPMs are rising you're feeding too much or if they're dropping your feeding too little. In 8 years of growing hydro my reservoir has never increased PPM by itself not even 10 PPM. But nobody tends to say how much lower or higher it's actually going when they say "oh well I need to feed it more/less". They don't say their 500ppm went down to 350 or their 500 went down to 545. I'm trying to find the happy medium between chasing ghosts in sensor drift and waiting for the problem to become big enough to be super obvious.

There are no ghosts to chase You are using the same meter and the readings will have the same error factor (if any) as when you used it last time. If your PPM went down from 500 to 350 that missing 150 PPM is not sensor drift the plant used 150 PPM of salts from the solution.

Like I make the reservoir now, and just throwing numbers at the wall, lets say after equalizing for an hour or two my measure the PPM and it is 400.

Now if I come back in 24hrs and that 400 PPM is now 250 I know very well that I have underfed and they need more nuts. No you did not under feed the plant! If your PPM went to zero then you might wonder if you underfed the plant but you could not know that with this information. Perhaps 400 PPM is exactly what the plant wanted that day? Your goal now is to replace the 150 PPM of nutrients the plant used. But how much of each N, P, K, Ca, Mg or S did the plant use? I know what to do then and how to get the nuts back up and all. Do Tell. But say instead I measure it after 24hrs and that 400 is now 390. That is not so clear. I personally would call that sensor drift. But I can't figure out where to draw that line so I know when to react.
No, that missing 10 PPM is not sensor drift. You are still using the same calibrated meter. The plant simply only used 10 PPM of salts from the solution. Replace the 10 PPM to regain your desired PPM.

 

[JoeCollins]

I'm sorry but you give meters way more credit for accuracy than they have. I worked in a lab setting testing solutions, and we would typically test three to five times and take an average of the results because they would be different because variance hits on every measurement. Now you meter probably isn't going to swing from a +50 variance to a -30 variance (tho it can!) but it may commonly go from a -50 variance to a -45 or a -40 variance or even the -30's.

I've even tested and confirmed this at home with a ~300$ blue lab meter myself, and if I tested on the side of the cup versus the middle of the cup I would get slightly different numbers as well as if I let the test cup set for several minutes and test it again I would get again a different result. Not hugely different but different.

 

[Mañ'O'Green]

I'm sorry but you give meters way more credit for accuracy than they have. I worked in a lab setting testing solutions, and we would typically test three to five times and take an average of the results because they would be different because variance hits on every measurement. Now you meter probably isn't going to swing from a +50 variance to a -30 variance (tho it can!) but it may commonly go from a -50 variance to a -45 or a -40 variance or even the -30's.

I've even tested and confirmed this at home with a ~300$ blue lab meter myself, and if I tested on the side of the cup versus the middle of the cup I would get slightly different numbers as well as if I let the test cup set for several minutes and test it again I would get again a different result. Not hugely different but different.

@JoeCollins You are growing plants with these tools and 50 PPM one way or another is not going to make a difference You are not in the lab.

Smoke some dope and grow some plants.

 

[JoeCollins]

@JoeCollins You are growing plants with these tools and 50 PPM one way or another is not going to make a difference You are not in the lab.

Smoke some dope and grow some plants.

Lord. I know. That is my whole point, where does...you know what nevermind, i have explained it so many times if you cant see what I am asking then you are trying NOT to see. First you try to tell me varance basically doesn't exist and the numbers are rock solid now it's just a small enough number not to worry about. You clearly see what I am asking but still are dancing around it and not wanting to answer the question I am asking but instead what to give me a line about how "meter is perfect just take the number and go bro"

Any are grow forums so useless? Oh right, bc yall are all too high to take a minute to actually read and comprehend what you are replying too and just info dump based off of a few keywords without reading the nuance of the question being asked. That or the entire grower network relys on this measuring equipment without any understanding at all of how they actually work, how to take measurements, and how to evaluate that info for errors on even the most BASIC level. Just take number and "randomly do something bc idk bro I have no idea what the plant ate anyway so what does it even matter??"

 

[blue]

It is an easy question to answer idk why you are so obstentantly refusing to do so. I can only assume you are here just to troll not to help.

Or just use your eyes when you use your meter. Take that as the "drift"
Problem solved.

Good bye mr bad attitude.

 

[Mañ'O'Green]

I was going to give him real nightmares because I was going to talk about the real Elephant in the hydro grow tent - PH

Logarithmic scale! Where 1 point can harm a plant and 2 can kill it.
Notoriously inaccurate meters that need to be calibrated and maintained regularly!
Primordial soup that can change the PH in minutes.
Root exudates that drop the PH in just a few hours.
Reservoir volumes that decrease because of root volume making it even harder to maintain PH........................................

 

[Mañ'O'Green]

@blue thanks for the rep!