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What is a Good pH/EC/TDS Meter?

Smokin Moose

Fallen Cannabis Warrior
I use and recommend the Hanna HI9813 Grocheck portable ph, ppm and EC meter. It is available from most larger indoor garden supply retailers for around $200. I have had one for several years and it never drifts more than .2 on the ph scale or 30ppm from the original calibration made. I keep the electrode immersed in Hanna storage solution and use a hand held trigger sprayer to clean the film and residue that accumulates on it. I feel this contributes to my consistent readings without any need for re-calibration at all.

Added by ~shabang~:
I've had the lower model waterproof Oakton pens for over 5 years with no problems. I've replaced the pH probe twice since I let it dry out too long, but I did that for piece of mind and not because it really needed it.

Marley Haze

New Member
Hey MED, I have that same Hanna. Can you tell me something. When I calibrate the PPM does the unit adjust for temp itself and I set it to 1500 or do I set it to the actual tempeture of the calibration fluid? I just checked it and i set it for 1604 at 82 degrees.

Then my next question would be if you use the 1604 x 2/1000, that equals 3.2ms/cm but my meter reads 2.17 Ms.

I think this meter is using 700 for a referrence

If Ms/cm is more accurate than PPM what do I use to calibrate Ms/cm?


How do I convert my readings from TDS to EC and vice versa?

To get the approximateTDS value, simply multiply the EC reading (in mircoSiemens/cm) by 1000 and divide by 2. To get an EC value, multiply the ppm reading by 2 and divide by 1000.
For example if your EC is 1:
1 x 1000/2 = 500ppm

And if your ppm is 500:
500 x 2/1000 = 1EC


New Member
May be a dumb question, but that's never stopped me before....is a TDS meter only needed if you have a hydro set up, or is it needed for soil as well?


New Member
nice but not necessary for soil for anewby :
litmis paper check of water nutes as mixed properly
and riunoff water couple times a month should be more than enough to get so first hand knowledge as you go
and give more options for control and knowing than no meter at all without costing much if you know or plan on switching to hydro you should plan investing in a good meter in your first equipments lists good liquid nutes with ACCURATE MIXING WITH DISTILLED WATER will give average ppm rates if you follow directions and your soil is balanced and not screwing your nutes this can happen if something is too much in your mix


I just picked up a Hanna TDS meter and the hydro salesman asked me whether I wanted it calibrated for 1382 or 1500. He said that by going with 1382 I am giving myself some buffer so I am less prone to mistakes.

Now I am new to hydro but not to growing. I feel like I would rather be calibrated for true readings so I learn what the plants really need. Alternatively I will go with training wheels if that is the recommended practice.

I would like to hear others chime in on the pros and cons of calibrating to give yourself some buffer vs calibrating for true readings. Would you switch to true readings or leave the buffer in? BTW I am using GH nutes with modified Lucas in passive hydro.


Never mind that last post - now I understand how this all works. the salesman was confused. You use the calibration solution for the conversion factor your meter is set to. I set the conversion factor to 0.7 and then calibrated with the 1500 ml solution. Had i used the 0.5 conversion factor i would have needed to use the 1382 solution.


New Member
you want to calibrate your meter to the number closer to what you think you'll be running, since the higher (or lower) your number from the calibration, the more the reading will drift (become less accurate) so for soil you would most likely want to use a lower calibration solution, higher with Hydro... ...this is not rule of thumb, but only a guide line since you could throw in some non-plant food solution into your nutrient mix, and the reading would potentially go way up.

with that said, you can and should use a tds tester for soil application to keep tabs on your fertilizer regimin. once you find the 'niche' you read TDS or EC and take note of it in the future so that you have a general guideline. after a few successful crops while testing both your nutrient solution and your waste water you should be able to test your nutrient solution/run-off and know exactly were you stand compared to your last crops. after a while using the same nutrients and concoctions you won't even need the tester. Your plants will talk to you if you only look and listen.

a good rule of thumb is to start lower with nutrient recomendations...say 75% of recommended dosage or less...and work your way up. When experimenting with a new strain I find that using half strength base nutrient and quarter strength on additives allows you to gradually increase to full strength without burning and stressing if you take the extra time in veg. This will also give you an idea of how the plant will react to the high nutrient and additive levels in bloom stage. I tend to use my EC/TDS pen to be sure that my nutrients are were I want them, not were the manufacturer recommends. The manufacturer doesn't take into account additives (macronutrients, micronutrients, amino acids, hormones, ect...) that will ultimatly lead you to decreased base nutrient TDS/EC levels. If your using the manufacturer recommended TDS/EC levels and adding other things to your mix then welcome to burn city. (BURN CITY BAAAAAAAD!!)

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Well-Known Member
Just a quick question. What About us poor retired growers who can't afford a 200 dollar meter?
mhhhhhh. Any suggestions for a reasonable price?
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