EC for noob

[SWvoodoo]

hey all and happy growing, another newbie to hydro here. Just a brief question on EC levels for a RDWC system. My understanding of ec levels in DWC is that I am trying to achieve a balance of the nutrient concentrate of my res vs the plants nutrient uptake is that correct? I think I read somewhere a 30ppm??? deficit every 48 hrs or something. so basically I should be running my nutes so they are slightly dropping in ec over a few days??
Have I got the idea roughly right ??
Any direction in the proper usage of an ec meter and ec levels in particular in rdwc would be much appreciated. thanks in advance and happy growing all!!!

 

[SWvoodoo]

No takers? Am I just way off the mark?

 

[GreatLife4All]

Welcome to the world of hydro...

First, let me say that EC is a parameter - and not a scale.

My understanding of ec levels in DWC is that I am trying to achieve a balance of the nutrient concentrate of my res vs the plants nutrient uptake is that correct?

Mostly correct, Yes. There are two things that you are worried about: the balance of elements in the nutrient solution, and the dilution rate of the nutrient solution.

I think I read somewhere a 30ppm??? deficit every 48 hrs or something. so basically I should be running my nutes so they are slightly dropping in ec over a few days??

Yes, over a period of time you should see the PPMs drop in the nutrient solution. Never heard 30 PPMs per day... And this would change over the life time of a plant in any case.

If things are working correctly, you should also see the pH increasing as the nutrient solution disappears.

You can either top off with a weak (say 75% strength) nutrient solution or simply use pH corrected water.

Any direction in the proper usage of an ec meter and ec levels in particular in rdwc would be much appreciated. thanks in advance and happy growing all!!!

Now this is where things will get interesting...

There are multiple names for various types of "EC" meters. The can be called TDS, EC, or PPM meters. But they are all basically the same. You can also get a combo meter: a single meter that measures EC and pH for example. TDS is usually the name applied to meters designed and calibrated to measure water quality. EC seems to be a catch-all name. And a PPM meter is typically for ionic solutions.

One of the harder things is knowing how to properly calibrate an EC meter. EC means electrical conductivity - and it is a measure of the amount of electricity that can pass thru water. The more dissolved solids in the water - the more electricity that can be conducted. But here is the thing, the types of solids in the water matter for how much electricity can be conducted - so you must calibrate the meter to the expected solution.

If you are wanting to measure the PPMs for R/O, tap, or well water - you should calibrate with a 442 solution. If you want to measure something with "salt" in it - then you should use an NaCl calibration solution. This is for use in salt water aquariums. If the water contains a lot of potassium, then you need to calibrate your meter using KCl. For hydroponics - you should calibrate your meter with KCl.

So if you buy a TDS meter - it will likely be calibrated using a 442 solution - and won't be accurate without re-calibration using a KCl solution. PPM meters are typically used for salt water aquariums - and so they will be calibrated with NaCl. If a meter is sold by a hydro company, it MIGHT be correctly calibrated.

In order to ensure accuracy, you also need to calibrate your meter with a solution that is close in PPMs to what you expect to measure. If you will be running your nutrient solution around 1,000 - then use a calibration solution that contains 1,000 PPMs.

And finally, temperature of the solution really matters when you are measuring EC. So a meter that does not do automatic temperature adjustments is not going to be accurate even if calibrated. But it can get you in the ballpark.

So... know what you are buying and how it has been calibrated. Get the proper calibration solutions so that you can ensure accuracy. Ensure that your meter does temperature correction.

 

[SWvoodoo]

Wow thanks heaps GL4A! I'd never seen anything about different calibration solutions so that is very handy. I was thinking of getting a meter similar to the blue lab truncheon, says it doesn't need calibrating? So basically ec rising solution too strong and vice versa? Sorry just trying to get my head around this. Thanks for your time

 

[Gelite]

One more thing, it is highly possible to evaporate water faster than your plants use the nuts in it, especially when the plants are young. A dwc system is constantly blowing dry air thru your Rez tank and it evaporates a bunch of water out of the tank especially when you figure your gonna be using the same nuts for a week or two. Trick is to evaporate it at the same rate the plants are using the nuts which doesn't usually happen. This is really why u need an ec meter. If u mix by the recommendations on the bottle u should be good, it's maintaining that same level of dissolved salts consistently. This makes knowing your level imparative. Don't be scared of the meters and calibrating and all that crap. Just get a meter that is for hydro gardening. I have a truncheon meter. It is for hydro systems and can not/does not need calibrating. It's set from the factory and never needs calibrating and even if it did it can't be done. I don't know what growers prefers these days but back in the day u weren't a real grower without a truncheon meter. I've had mine for 10 years and it was probably 10 years old when I got it so I mean there like fuckin impossible to break. I think they still make an up to date version or older ones are available online.

 

[SWvoodoo]

Awesome thanks Gelite it should be here tues so hopefully im not disappointed.

 

[Gelite]

Hey bro u can't go wrong with a truncheon. Yeah they make meters that will tie your shoes and give u head but I'm very capable of tying my shoes and my old lady gives better head so basically all that extra shit does is cost more, needs constant recalibration, it's confusing as fuck and over complicated. You can't be certain that your getting an accurate measurement unless your positive that you calibrated it right. There is no guesswork with a truncheon. They are just too simple to fuck up. Mine is like frighten serial number one so I would like to know how it reads compared to your new one. Let me know when it arrives.

 

[SWvoodoo]

Advertising reads:
•
Measure EC (Electricity Conductivity), CF (Conductivity Factor) and PPM (parts per million) in one stick

•
High conductivity measurement for wide range of crops

•
100 % Fully Waterproof

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Easy to use, no external buttons

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Automatic Power On / Off when the meter senses solution

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Built with Automatic Temperature Compensation (ATC)

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Factory pre-calibrated


Specifications:
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Measuring range:
◦
CF: 4 ~ 52 CF

◦
EC: 0.4 ~ 5.2 EC

◦
TDS: 280 ~ 3640 ppm (EC x 700)

◦
TDS: 200 ~ 2600 ppm (EC x 500)


•
Resolution:
◦
CF: 1 CF

◦
EC: 0.1 EC

◦
TDS: 70 ppm (700 conversion factor)

◦
TDS: 50 ppm (500 conversion factor)


•
Accuracy: ±4 % of reading

•
Automatic Temperature Compensation: 0 ~ 50 °C (32 ~ 122 °F)

•
Operating Temperature: 0 ~ 50 °C (32 ~ 122 °F)

•
Calibration: Factory pre-calibrated

•
Automatic Power On / Off

•
Power: 3 x 1.5 V AA Batteries (Included)

•
Item Size: approx. 415 (L) x 23 (W) x 23 (D) mm (16.3' x 0.91' x 0.91' inch)

•
Item Weight: approx. 179 g

I will definitely post up how I rate it.