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Can You Help Me Figure Out What My EC Pen is Trying to Tell Me

GreenArmadillo

GreenArmadillo

New member
Hello one, hello all.
Just recently started using EC/TDS readings, so totally a noob here. I'm using a cheap EC/TDS pen, so there's one or two things i'm trying to figure out.

3in1-Digital-Water-Quality-Tester-LCD-font-b-TDS-b-font-EC-Water-Filter-Purity-Pen.jpg
PENTYPE-TDS-METER.jpg



Firstly, I wanted to calibrate this thing, so I got the bluelab 2.77 EC calibration solution. (=1385 ppm with 500 scale, =1940 ppm with 700 scale)
Now the problem with this cheap-ass pen is that it has no calibration option. No calibration button and no screw to dial in.

So I dip the pen into the calibration solution, and it reads:

3556 uS/cm2 = 3.56 mS/cm2 = 1775 ppm

(Calculating 3.56*500 equals 1780, so therefore this pen uses the 500 scale, which is the NaCl scale)


Now comparing that to the calibration values:

3.56-2.77= +0.79 difference in EC
1775-1385= +390 difference in TDS

So my pen is 0.79 over the EC value it should be reading, and 390 over the TDS value.
Does this mean that if I subtract these values from all future values it will be giving me an accurate reading?
 
Picking up from there, I have some values from when I fed the gals nutes, and from when I gave just good ole water.

[TABLE="border: 1, cellpadding: 1"]
[TR]
[TD] Type of Feed[/TD]
[TD] EC[SUB]in[/SUB][/TD]
[TD] TDS[SUB]in[/SUB][/TD]
[TD] EC[SUB]out[/SUB][/TD]
[TD] TDS[SUB]out[/SUB][/TD]
[TD] Calculated EC[SUB]in[/SUB] || Calculated TDS[SUB]in[/SUB][/TD]
[TD] Calculated EC[SUB]out[/SUB] || Calculated TDS[SUB]out[/SUB][/TD]
[/TR]
[TR]
[TD] Nutes[SUB]Daphne[/SUB][/TD]
[TD] 2760 us/cm[SUP]2[/SUP][/TD]
[TD] 1372 ppm[/TD]
[TD] 3555 us/cm[SUP]2[/SUP][/TD]
[TD] 1783 ppm[/TD]
[TD] 1970 us/cm[SUP]2[/SUP] || 982 ppm[/TD]
[TD] 2765 us/cm[SUP]2[/SUP] || 1393 ppm[/TD]
[/TR]
[TR]
[TD] Nutes[SUB]Esmerelda[/SUB][/TD]
[TD] 2760 us/cm[SUP]2[/SUP][/TD]
[TD] 1372 ppm[/TD]
[TD] 3223 us/cm[SUP]2[/SUP][/TD]
[TD] 1613 ppm[/TD]
[TD] 1970 us/cm[SUP]2[/SUP] || 982 ppm[/TD]
[TD] 2433 us/cm[SUP]2[/SUP] || 1223 ppm[/TD]
[/TR]
[TR]
[TD] Water[SUB]Brittania[/SUB][/TD]
[TD] ?[/TD]
[TD] 116 ppm[/TD]
[TD] 3560 us/cm[SUP]2[/SUP][/TD]
[TD] 1765 ppm[/TD]
[TD][SUP] ?[/SUP] || 116 ppm[/TD]
[TD] 2770 us/cm[SUP]2[/SUP] || 1375 ppm[/TD]
[/TR]
[TR]
[TD](Calibration Liquid)[/TD]
[TD] 3556 us/cm[SUP]2[/SUP][/TD]
[TD] 1775 ppm[/TD]
[TD] -[/TD]
[TD] -[/TD]
[TD] 2766 us/cm[SUP]2[/SUP] || 1385 ppm[/TD]
[TD] - || -[/TD]
[/TR]
[/TABLE]


* Water used was bottled water, which claims 116 ppm as the TDS written on the bottle
* EC calculated by subtracting 790 ms/cm[SUP]2[/SUP]
* TDS calculated by subtracting 390 ppm



So what does this mean for my girls?
They are in week 5 flower, so do these values make sense?
I am using GO nutes, according to this schedule (more or less, I don't have CalMag so adding epsom salts and an amino calcium feed):

GO Schedule.jpg



Any and all help is greatly appreciated.
One love homies and homettes. :laugh:
 
Yes you should do it for practical purposes but the convertions are not linear. That's why manufacturers recommend calibrating with the same (scale) solution the software is for. So a 500 scale pen is going to read more accurately around 500 Ppms. Same with the 700 scale. What you are going to do substracting values is the same that the calibration screw would do.
 
Okay, that's a good start.

As for my values for the plants themselves. Do they look good, or is something off?
Like especially the fact that my values coming out of the soil are higher than the values going in. Common sense had me thinking that it should be the opposite due to the gals drinking up nutes.
I'm week 5 flower, but i'm growing a sativa, so its quite possible my flowering stage will last anywhere between 10-15 weeks.
 
I think those values are super high. Dangerously high. I wouldn't go over 1 EC or 500 ppm during veg and 2 EC or 1000 ppm during heavy feeding flowering
 
But hot soil like fox farms usually when first watered with 15 ppm water it comes off around 3000 ppm or 6 EC. I just rinse the soil before planting. Mix with perlite 1/4 and give plain 15ppm water until runoff is less than 1000 ppms. This ensures no burn to the little seedlings but i "waste" what's in the soil. I start adding mainly calmag and some bloom P and K once is flowering. I never give the plants more than 750 ppm or 1.5 when mixing he solution. Just adding water to the soil makes the nutrients in there available so EC it's always going to be higher inside the soil and in funoff
 
If you cannot calibrate your pen then the only way you can use it is by figuring out the discrepancy in accuracy as you have done, but in reality the meter is reading the electro conductivity of the solution and any error will be not as a definite number (390 ppm) as you found out but as a % error instead.
3.56-2.77= +0.79 difference in EC
1775-1385= +390 difference in TDS or 22% error
The error is 390 when testing a1385 solution but would not be the same with a different strength solution
At 1000 ppm the error would be 220 ppm and at 2000 ppm the error would be 440 ppm. Or 22 %
Hope that helps
 
Guys, I need your help once more.
I fed the girls their weekly nutes yesterday, and honestly, the run off number were alarming. Check it out:
(PS. Both Alicia and Brittania were transplanted to bigger pots over the past 3 days, with some new fresh fox ocean forest, so that is probably the reason their run-off is spiked way higher than Daphne and Esmerelda, who were both transplanted slightly earlier.

Daphne Transplant: 21/3/17
Esmerelda Transplant: 28/3/17
Brittania Transplant: 31/3/17
Alicia Transplant: 1/4/17


Mixed a 3.5 gallon batch:
pH[SUB]in[/SUB] = 6.4
EC[SUB]in[/SUB] = 1,388 uS/cm[SUP]2[/SUP] = 1.39 mS/cm[SUP]2[/SUP]
TDS[SUB]in[/SUB] = 640 ppm

*all values calculated by percentage, as growmore suggested to me above: EC = EC[SUB]pen[/SUB]-(EC[SUB]pen[/SUB]*22%) and TDS = TDS[SUB]pen[/SUB]-(TDS[SUB]pen[/SUB]*28%)

[TABLE="border: 2, cellpadding: 1, width: 700"]
[TR]
[TD] [/TD]
[TD] Run-Off pH[/TD]
[TD] EC[SUB]out[/SUB][/TD]
[TD] TDS[SUB]out[/SUB][/TD]
[/TR]
[TR]
[TD] Alicia[/TD]
[TD]6.25[/TD]
[TD] 4468[/TD]
[TD] 2090[/TD]
[/TR]
[TR]
[TD] Brittania[/TD]
[TD]6.00[/TD]
[TD] error (>9999)[/TD]
[TD] 5920[/TD]
[/TR]
[TR]
[TD] Daphne[/TD]
[TD]6.39[/TD]
[TD] 2272[/TD]
[TD] 1048[/TD]
[/TR]
[TR]
[TD] Esmerelda[/TD]
[TD]6.34[/TD]
[TD] 7360[/TD]
[TD] 3385[/TD]
[/TR]
[/TABLE]


Should I be worried? The run-off numbers are for the most part way higher than what 9fingerleafs recommended.
Or were you referring to the numbers going in when you said:
"I wouldn't go over 1 EC or 500 ppm during veg and 2 EC or 1000 ppm during heavy feeding flowering"


Either way, I want to know if i'm doing things right, or something i'm doing is wrong.
Reason i'm asking so persistently is so that I can catch my mistakes early and sort them out before they cause real damage.


Love the support here guys. Thank you all. <3
 
Yes. I was referring to the water going in taking in consideration you have a nutrient rich soil (just like I do) so at any point that's the highest I would feed cause there's always going to be new nutrients available from the soil as you provide water and the microbial processes occur on the roots. This is also based on watching numerous professional growers running hydroponics on soiless medium. They follow manufacturers nutrients regimes cause they are made for this kind of growing. We use soil and hydroponic nutrients so we have to be careful cause they're not designed to be used this way. This is a big problem not addressed on the main site (I think) and creates a lot of confusion among new growers. I've flushed happy frog soil to the point of <200 ppms and a week later the runoff is around 1000ppms.

personally I go very easy on the nutes except for calmag cause my water is 10-15ppms and very ph volatile. I'd advise you to water small amounts of low EC water at first without any runoff. The runoff is a must ify ou give nutrients all the time cause you don't want to saturate the medium. But this is not the case if you want to use what's in your medium. I wouldn't worry much about those numbers cause of the soil. Give them low EC Water with lots of runof for now and go easy on the nutes. You have to find what works for you and give the plant the chance to feed from the soil. I'd come to the conclution that in the future I will use coco to have more control over the nutrients
 
Plants transpire water through there leaves and take up the nutrients while doing so and if the nutrient level is higher than they need or can use the the ppm of the nutrient solution increases. Basically if your plants need 500ml of water per day they will drink that much and the nutrients available are greater that they need the ppm will theirfor increase.e.g. Ppm available to plants to high equals high ppm in runoff ppm to low then low ppm runoff.
 
Cool. So ideally, if I have everything dialled in perfectly, my run-off should be close to zero ppm, correct?
Cause I would be feeding my plants exactly the amount of nutrients they need, so they would suck them all up and the water coming out would have no nutes left in it.
This would mean that with my current high ppm run-off, it is a sign that I don't understand my plants, and am overfeeding them. Am I correct in saying this?

Did I understand your meaning correctly?
 
Awesome!! With all that was said, it seems I should only be giving water for the rest of this week as well as the next.
So tomorrow was a water-only day anyway, so that's what i'll do. And instead of giving them a nute feed on Saturday, i'll only give them water. (My bottled water is already at pH 6.5 with a small amount of nutrients @ 116ppm so should be light enough). I'll be watering until I get minimal run-off, maybe less than 10%, and test the pH and EC/ppm.
Then next week, Tuesday is a water-only day. Based on my run-off ppm/EC on Tuesday, i'll come back here and post up, and see if I should feed the gals nutes on Saturday 15th of April. That will have given the gals 2 weeks of no nute feedings, since they all have some new FFOF to use up after having been transplanted.

Sound about right?

By the way, what about CalMag. Should I be adding that to my water-only feeds?
I recently received some GO CalMag+ through the mail, so I can finally give the girls some. I had calmag issues during the early flowering phase, so I don't wanna risk getting them again.
And should I be watering until excess run-off during any of these water-only feeds? Kinda like a mini flush?


It might be important for me to add that I have had some leaf issues and symptoms these last two weeks, so it all might be related.
If you have the time and don't mind, could you hop over to my thread about my leaf symptoms, and check out the most recent posts. I think I have some deficiencies/lock out. Something's definitely not right.
I'd really appreciate it.

forum.growweedeasy.com/forum/growing-community/62637-1st-lemme-say-hi-then-lets-diagnose-mid-lower-leaves-sick-blotches-brown-edges/page2

Armadillo love. :smooch:
 
I think you should add a little bit now and then it's always good. About the pot size and plant size and flowering progress in going to take a guess at it.
In my opinion you got there a long flowering sativa that needs more light than it has and due to this slow progress the plant has outgrown the pot which means very little medium left which means it may lack some nutrients. If I where you I'd start some new seedlings and give this plant time to do what it needs to after transplanting to a bigger pot and giving more light (if posible) but mainly try to learn so you don't make the same mistakes. Get some more plants and keep experimenting. Don't put all your eggs in the same basket
 
No the point I am making is that the ppm out should be close to the ppm in. Whatever ppm you want to feed should be adjusted so that the runoff is what you actually want.You are using a soil mix that already has a ppm value even if you water with plain water so if that has a higher ppm than you want then you would water with plain water and if is lower then you would make up your nutes you want to give you your desired ppm. Example, soil with a ppm value of 500 and you want to feed at 1000 ppm then you would make up your nutes at 500 ppm.
 
That's spot on growmore. Understanding that, one must get to know his soil, plants and water to get the best of them. Learning how they behave under different feeding and watering techniques and doses. I personally think that with a soil like fox farms ( that is very little "dirt" and it's mostly hummus and organic matter with a bunch of beneficial fungi) there's little to be added. We all feed like if we were running hydroponics
 
9fingerleafs You make a good point about overfeeding when using mix that has a nute value of its own. The only way to use these types of mix is knowing what their inherent nute value is and once you know that, you at least have a good starting point. I grow hydro for the simple reason that with mix you can measure the ppm of your mix but you still have no idea as to what is contributing to that ppm. So I could have a high ppm but have a N deficiency in veg and have a low P and K when flowering.
 
No you probably should not have. as your ppm reading of the runoff is way to high. Whenever you repot them your first watering should always be with no nutes added until you know what the ppm of the runoff is. With So high nute levels you run a very real chance of damaging the roots and stopping them from taking up water and becoming dehydrated.
 
Woah, that's deep.
I see what you guys are saying.

Well, in that respect, is there any form of table or schedule that describes optimal ppm levels at the different stages of a plants life?
I think having benchmark numbers to aim for would make this a lot more doable.
Then as you say, it would be a matter of mixing up your nutes so that they complement the soil, and together give a total ppm run-off that is desirable.
(Instead of blindly following the nute manufacturers schedule)

Really love the details being provided. I feel like i'm becoming so much more knowledgeable.
 
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