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Necessity of EC meter

LiberalThinker

Well-Known Member
Hi. First post. I'm dipping my toes into DWC. I have a 70 litre Oxypot XL which will have one plant and was wondering if an EC meter is really necessary if I change the General Hydroponics Flora solution every 7-10 days. I will be maintaining pH with a chemical test kit. I plan on using this feed schedule below, which is a plan based on the General Hydroponics schedule but the doses are reduced. This is a tried and tested plan by someone on another site. My main thought is: would the nutrient concentration reduce too much when it's larger to last it until the next nutrient change?

1741381

Light -wise it will be under up to 600w Sodium eventually. I have a 600w variable wattage ballast and dimmable Phillips 600w Green Power bulb. I have several indoor soil grows under my belt but hydro is new to me.
 
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Old Salt

Member of the Month: Apr 2019
Yes, a TDC/EC and pH meter are both crucial to the success of a DWC grow. As water evaporates from your system the PPM/EC of your nutrient solution will change. The TDS/EC meter lets you monitor this, and bring it back to where it belongs. Keep records of how nuch water you add to make this easier in the future. It's the same with pH. The plants drawing the nutrients up, and the air bubbling through your solution will change the pH. You need to bring that back to where it belongs as well. These tasks need to be done daily until you get a feel for your grow.
 

Old Salt

Member of the Month: Apr 2019
These are not very expensive, so go for the best accuracy you can afford. General Hydroponics publishes the EC/PPM of their mixed nutrient solutions, so make certain the range of your meter covers it. Also get a calibration solution for the meter, as an uncalibrated meter is worse than none at all. The calibration solution you buy should be as close to the readings you expect as possible.
 

LiberalThinker

Well-Known Member
These are not very expensive, so go for the best accuracy you can afford. General Hydroponics publishes the EC/PPM of their mixed nutrient solutions, so make certain the range of your meter covers it. Also get a calibration solution for the meter, as an uncalibrated meter is worse than none at all. The calibration solution you buy should be as close to the readings you expect as possible.
My idea was to measure the EC values of the doses in the feed schedule above and maintain them for the required duration. Will that approach work? I will buy a calibration solution though, and whatever necessary to keep the meter in optimal condition.
 
I got one and always on ph/EC meter for 30 GBP on Amazon... seems to range in price by +£20 or so from different suppliers.

It has been fine as I have a BlueLab to compare the two.
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
Necessity? No, not really. If I was using test strips to monitor/adjust pH, and only had the money to purchase either a decent pH meter or a decent EC meter, I'd probably buy the decent pH meter and use my DVOM to measure electrical conductivity.

Why? Because the pH scale is a logarithmic one, so if I can only reliably detect a change of 1.0 pH, that's not good enough for hydroponics use. A solution that has a pH of 5.5 is ten times more acidic than a solution that has a pH of 6.5. And that's not even taking into consideration factors such as the possibly not perfect color perception of the person doing the testing, the possibility that the nutrient solution (which is generally never clear) might influence the color, et cetera.

So I'd buy a decent digital pH meter and grab the DVOM from my toolbox, along with a calculator (or pencil and piece of paper, lol) and ruler, and use those to measure EC. Like so:

William Hirsch said:
By touching the negative and positive leads of a multimeter that is on in the resistance setting allows you to measure the conductivity of water, a test of its purity. When water conducts electricity, it is made possible by water impurities such as metals. The standard unit of measure for conductivity is microsiemens per centimeter (µS/cm). For aquarium enthusiasts, for example, most fish in the United States thrive in water with a conductivity between 150 and 500 µS/cm, while rivers have a range of conductivity between 50 to 1500 µS/cm. Conductivity relates to the resistance to current flow of the water.

Pour the water to be tested into the glass backing dish.

Plug the red and black leads of the multimeter into its positive and negative ports, respectively. The red lead represents positive, while the black lead represents negative.

Turn on the digital multimeter and then switch its measurement dial to the resistance setting. Resistance is denoted by the capital Greek letter omega (Ω). Omega represents the symbol for the ohm which is the unit of resistance.

Touch the leads to the water at opposite ends of the longest dimension of the glass dish. Note the resistance in ohms that appears on the screen. For example, assume a resistance of 33 ohms.

Measure the length, width and depth of the glass dish in centimeters. For example, use a length of 30 cm, a width of 15 cm and a depth of 3 cm.

Multiply the width by the depth to obtain the area of the sides of the glass dish in square centimeters. Using the figures in the example results in 15 cm times 3 cm, or an area of 45 square cm.

Divide the length by the product of the resistance and the area to arrive at the conductivity in units of siemens per meter. This yields 30 cm divided by 33 ohms times 45 square cm, or a conductivity of 0.02 siemens per meter. The siemens units equals one divided by the ohm.

Convert the conductivity to microsiemens per cm (µS/cm) by multiplying by 10,000. The prefix micro translates to one-millionth of a siemens. Finishing the exercise, results in 0.02 times 10,000, or a water conductivity of 202 µS/cm. This is in the inhabitable range for some types of fish.
Having an EC meter makes measuring EC easier, of course ;) .

Get both a pH and EC meter, if at all possible. DWC isn't soil, lol, its a form of hydroponics. It's easy to grow great plants - if you have the proper tools.
 

Northern Hydro

New Member
Hi. First post. I'm dipping my toes into DWC. I have a 70 litre Oxypot XL which will have one plant and was wondering if an EC meter is really necessary if I change the General Hydroponics Flora solution every 7-10 days. I will be maintaining pH with a chemical test kit. I plan on using this feed schedule below, which is a plan based on the General Hydroponics schedule but the doses are reduced. This is a tried and tested plan by someone on another site. My main thought is: would the nutrient concentration reduce too much when it's larger to last it until the next nutrient change?

1741381

Light -wise it will be under up to 600w Sodium eventually. I have a 600w variable wattage ballast and dimmable Phillips 600w Green Power bulb. I have several indoor soil grows under my belt but hydro is new to me.
This is a Recycling nute schedule ..(.RDWC) you are looking for a drain To waste schedule? One bucket soup right ? Slightly different #'s ..
Yes you need meters . Good luck!
 

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WankirA

Well-Known Member
This ec meter is a funny business. Looking at how 'necessary' an ec meter actually is. It seams having one comes with its own set of problems.

Im getting where @Barney86 is coming from in relation to measurements within a "water based system": although looking at @Northern Hydro 's charts i'm also guessing the nute lines themselves dictate a (brand specific) feeding schedule ?!?!

Not sure the measurement is as simple in soil &/or coco based grows.
(Only just realised soil n coco not a good mix?!) But this begs a potentially 'egg on my face' question if you folks dont mind:

How is a perfect measurement (for that strain, that time in seed/veg/bloom, for that temp, for that medium, for that light sytem etc etc...) decided in the first place???

Please forgive my ignorance on the subject, im still a newbie and only have so many hours In a day.
Additionally because my initial budget was tight, I decided after some revision, that an ec pen wasn't 'absolutely required' and given when I first saw them (local grow supplies) they were £70+, I stopped looking into them; once i made that decision i stopped looking at it as on my list of 'need to knows'. However, obviously more important than I thought (for plants health and by extention on a positive yield) and if worth doing - an absolute must.
Have ordered one now ive kicked into my budget (along with the ph meter being 3 weeks on its way from china!) So needing to dig into this if I'm ever to supply nutrition in a proven and measurable way.

Cheers in advance.
W
:thumb:
 

Old Salt

Member of the Month: Apr 2019
I'm in the camp that a TDS meter to measure PPM or EC is not needed for drain to waste hydroponic systems. I have one, but only use it to check my RO. The TDS meter is an absolute necessity for any other hydroponic systems I know of, as you need to top up the nutrient solutions for them and the TDS meter is used to measure the solution's strength.

A means of measuring pH is an absolute necessity for any hydroponic system, drain to waste, or any other form.
 

Barney86

Well-Known Member
This ec meter is a funny business. Looking at how 'necessary' an ec meter actually is. It seams having one comes with its own set of problems.

Im getting where @Barney86 is coming from in relation to measurements within a "water based system": although looking at @Northern Hydro 's charts i'm also guessing the nute lines themselves dictate a (brand specific) feeding schedule ?!?!

Not sure the measurement is as simple in soil &/or coco based grows.
(Only just realised soil n coco not a good mix?!) But this begs a potentially 'egg on my face' question if you folks dont mind:

How is a perfect measurement (for that strain, that time in seed/veg/bloom, for that temp, for that medium, for that light sytem etc etc...) decided in the first place???

Please forgive my ignorance on the subject, im still a newbie and only have so many hours In a day.
Additionally because my initial budget was tight, I decided after some revision, that an ec pen wasn't 'absolutely required' and given when I first saw them (local grow supplies) they were £70+, I stopped looking into them; once i made that decision i stopped looking at it as on my list of 'need to knows'. However, obviously more important than I thought (for plants health and by extention on a positive yield) and if worth doing - an absolute must.
Have ordered one now ive kicked into my budget (along with the ph meter being 3 weeks on its way from china!) So needing to dig into this if I'm ever to supply nutrition in a proven and measurable way.

Cheers in advance.
W
:thumb:
It's even simpler in Coco mate. Just feed quarter of the full recommended dose from seedling to chop. Bit less for seedlings. Bit more if they get over the 5oz mark and start going yellow.
Feed every day at the right pH and literally nothing can go wrong :)
All there is to it :)
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
This ec meter is a funny business. Looking at how 'necessary' an ec meter actually is. It seams having one comes with its own set of problems.
Problems? Unless you consider having to learn how to do a ridiculously simple calibration once in a blue moon and having to figure out which way the batteries go in when it's time to replace them (also once in a blue moon) to be problems, then I don't know what you could possibly be referring to.

Please list these problems for us.
 

WankirA

Well-Known Member

WankirA

Well-Known Member
Bit more if they get over the 5oz mark
Is there a rule of thumb for telling if it is gonna be 5oz plus?! Or just judging by stature???
Sorry if a daft question but kinda figure it was simply unknowable till it comes to last week or two, and even then only a guessitmate....?!?!
At the moment, though not expecting certain numbers (esp for first grow!) But figure a couple to 3 o's wouldnt be a bad start for this noob.
Cheers
W
 

Old Salt

Member of the Month: Apr 2019
How is a perfect measurement (for that strain, that time in seed/veg/bloom, for that temp, for that medium, for that light sytem etc etc...) decided in the first place???
Trial and Terror.

Is there a rule of thumb for telling if it is gonna be 5oz plus?! Or just judging by stature???
It's usually an optimistic guesstimate. I didn't worry about it for my first grow. That provided a benchmark for that strain under my growing conditions. From there I tried to improve and push things a little with my nutrients. I had 32% more from my second grow of that strain. You should be able to get a minimum of 1/2 oz per sq ft of canopy for your first grow. You'll probably get more, but count that as a bonus. I got a little over 17 gm / sq ft for my first grow. The second was up to 22.5gm / sq ft for my second grow of that strain. I expect that to go up significantly for my next grow of that strain, since I have better lights now.
 

Barney86

Well-Known Member
Is there a rule of thumb for telling if it is gonna be 5oz plus?! Or just judging by stature???
Sorry if a daft question but kinda figure it was simply unknowable till it comes to last week or two, and even then only a guessitmate....?!?!
At the moment, though not expecting certain numbers (esp for first grow!) But figure a couple to 3 o's wouldnt be a bad start for this noob.
Cheers
W
If they get hungy mate then the first thing to appear is Nitrogen deficiency ( N Def)
It shows up by the bottom leaves going yellow from the tip backwards. Doesn't cause any damage though cos you'll lose those leaves eventually anyway one way or another.
If the yellow happens then go up by 50%.
If you manage to get them big enough to go yellow again then up it 50% again.
If you always wait for the deficits to appear then go up by 50% youre pretty much garunteed to keep everything in the right range. :)
Once you've done a few grows with your set up you'll be able to judge how big they'll be but it's pretty hard for anyone to accurately guess what your plant will weigh at any time. Some sites do guess the weight competitions and plants that turn out to be 20oz are guessed everywhere from 5oz to 50. Just have to figure that one out for yourself with a bit of trial and error :)
 
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Barney86

Well-Known Member
Ooooooohhhhh ....... Just realised a massive flaw in all my explanations.
The bottom leaves will also go yellow naturally but all over at the same time. They literally get cannabalised by the plant in every way if they're not getting enough light.
Sounds like a small thing but makes a massive difference. Bollocks. Think I'll need to find an admin to let me edit my feeding thread to include that or I could cause some problems. Don't want that hanging over me lol.
 
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