Lets talk about pH testing.

[aisach]

pH Testing
A little background on it. pH is the function of hydrogen. A gaseous element.
A mathematical logarithm.
Little p, big H; pH.

I admit to miswording the description.
Little mooover writes:
Correction... pH is the logarithmic function of the hydronium ion => H3O+ , also known as protonated water.
It is not a function of the gaseous element hydrogen.

The number one interference for a proper pH result is temperature. That is why all pH readings are combined and recorded with temperature measurements.
The higher the temp - the lower the pH. The lower the temp - the higher the pH.
Keep your feeding solutions and your feeding/flushing water at a constant temp. 20-25 dg C. 70-75 dg F. Should be optimal room temp.

All pH instruments should come with manufacturers instructions. Please read them. If they don't tell you how to care for the equipment, call the manufacturer and ask them. They may also have calibration, storage, filling, and cleaning solutions.
PS I know chemists that don't like to read instructions, so don't feel like you are alone if the idea frustrates you. LOL

Common choices for pH measurement are indicator tests such as color changing solutions, and indicator strips. These both come with a comparator chart for guessing, hence, they are not very accurate. Its guess work based on your brains ability to differentiate the nuances in a shade of color.
Then there are meters. From pens to probes (ion electrodes). It goes without saying that an ion probe is the highly desirable choice.

I need to find a couple pictures and look for some additional info before my next post.
But feel free to comment or ask questions.
aisa

 

[aisach]

DOER said

[Strips are fine when things are fine. But, when it goes to hell, probes and meters are your only tools in Hydro.

The pH can bang on material rotting in the roots, in the pipes. The spot for pH spot checks can be fine while the pump bucket has gone sideways with a clog.

And if the pH is stalled,and not moving, that is strange. Going in the wrong way for the time of day, is strange. Start at the Pump. I will likely find a clog in the pump impeller. No flow, discovered by the monitoring the probes.

I have an EC/PPM pen that only was $32. pH probes...I have a 1/2 a dozen, I ruined. They can't ever dry. I use a Tri-Meter, which is finicky, but can be calibrated. Need the calibrator solutions. Also pH probes need frequent calibration. I check them each month.

I just got the BlueLab pH Pen for $80. Dry it...Ruin it. It was that or another $200 Tri-Meter for the grow tent.

I also have a 1/2 dozen probe that do work. How to keep them wet? In an open jar? No. It will dry out and ruin. Maybe a big sealed jar? But, you don't want the BNC connector to rust out....Been there.

I toss them where it is never dry. In the res. BNCs on the dry floor.]

 

[aisach]

Yes a dry pH probe is trash-worthy.

Let me look up some info and find a couple pictures and get back to you.

 

[budbro18]

i got a cheap yellow hanna look a like from ebay for 8 bucks and its tried and true.

ive had it for about a year and its only really been off .1-.3 every time i calibrate. I keep the end in the ph 7.0 or 7.1 calibration solution when its not in use.

at first id calibrate it every week or so because it was so cheap. but now i go 3 months without calibrating and its rarely more than .2 off.

heres the same one i got, but probably not form the same ebay seller: http://www.ebay.com/itm/LCD-Display-Digital-PH-Meter-Measure-Tester-Pocket-Mini-Pen-Aquarium-Pool-Water-/140869621533?pt=LH_DefaultDomain_0&hash=item20cc7bd71d

mine was from china but this seller probably just buys em in bulk and sells em for faster shipping times.

 

[dlftmyers]

i got a cheap yellow hanna look a like from ebay for 8 bucks and its tried and true.

ive had it for about a year and its only really been off .1-.3 every time i calibrate. I keep the end in the ph 7.0 or 7.1 calibration solution when its not in use.

at first id calibrate it every week or so because it was so cheap. but now i go 3 months without calibrating and its rarely more than .2 off.

heres the same one i got, but probably not form the same ebay seller: http://www.ebay.com/itm/LCD-Display-Digital-PH-Meter-Measure-Tester-Pocket-Mini-Pen-Aquarium-Pool-Water-/140869621533?pt=LH_DefaultDomain_0&hash=item20cc7bd71d

mine was from china but this seller probably just buys em in bulk and sells em for faster shipping times.

I think its a hit or miss with those Chinese versions I bought one it lasted about 4 months but then again it was only like $8.00 i guess it might be how i took care of it. Here is another cheap one if anybody is interested in one:http://www.amazon.com/BestDealUSA-PH-009-Meter-Digital-Tester/dp/B0087LOWIA/ref=lh_ni_t?ie=UTF8&psc=1&smid=A29FWSGLLL6SOQ

 

[aisach]

Awesome.

In Budbro18's picture you can see the glass electrode bulb.

Storing in buffer 7 is ok. The industry storage solution is KCl (potassium chloride).

Frequent calibration is desired, of course, but since you know your system well, less is working for you.
Calibration should depend on the frequency of use. If you use it daily, then a weekly cal is probably good.
If you use it weekly to monthly, then monthly is ok.
The point is to verify the calibration is in the range you are testing, and that it is not drifting.
If you see it starting to drift beyond the +/- 0.3 pH units then you might need to look into replacement.
The glass bulbs do suffer etching, scratches, and fractures during normal use.

Those that measure pH daily, or several times a day should be calibrating daily, and verifying daily with a buffer 6.
A two pint cal would use buffer 4 and 7, or buffer 7 and 10. Verification can be done with buffer 6 or 7.
A three point cal would use 4, 7, and 10. Verification with buffer 6 or 7.

If your meter gives you a slope. write it down when you calibrate.
Slope is determined by the probe manufacturer (see the manual), and not by the meter manufacturer.
If you see excessive drift, get a new probe.

 

[dlftmyers]

Here is a P.h. chart for cannabis and check the link out he is talking about pumpkins but the same concept can be applied for cannabis http://www.team-pumpkin.org/downloads/Niagara2013.pdf

 

[main cola]

Here is a P.h. chart for cannabis and check the link out he is talking about pumpkins but the same concept can be applied for cannabis http://www.team-pumpkin.org/downloads/Niagara2013.pdf

Thanks for that chart and the link

 

[aisach]

Yes great chart. It stresses the importance of an accurate pH reading. The differences are only 0.6 and 0.5 pH units apart.
That's what makes proper maintenance and calibration verification really important. That narrow range of acceptability.

 

[jondamon]

Having contacted BLUELAB when I purchased my PH pen they recommend storage if their pen in either TAP WATER or KCI SOLUTION. Only one or the other.

NOT BUFFER 4 or 7 EITHER.

They mention the use of buffer 4 in their literature with the pen. They have since been in touch with the printers to adjust any further literature to state tap or KCI only.


Just wanted to add this seeing as you just bought one.



J

 

[aisach]

An important message on following the manufacturers advice on storage, etc.

And never use DI water. Mineral water is probably ok.

 

[Doer]

Having contacted BLUELAB when I purchased my PH pen they recommend storage if their pen in either TAP WATER or KCI SOLUTION. Only one or the other.

NOT BUFFER 4 or 7 EITHER.

They mention the use of buffer 4 in their literature with the pen. They have since been in touch with the printers to adjust any further literature to state tap or KCI only.


Just wanted to add this seeing as you just bought one.



J

Yep and soap clean it before calibration.

Mine won't calibrate so, I guess I need a replacement.

It wiil hit 7 just fine, but with 4 pH it says ER.
And there is not the checkmark next to pH, to say it completed.

I guess I will try 10 pH standard and see if that works.

I just swish in suds, and rinses and store in tap water each time. And try to remember to use it a lot. I don't know how long the water lasts in the cap and don't want to find out.

 

[jondamon]

Yep and soap clean it before calibration.

Mine won't calibrate so, I guess I need a replacement.

It wiil hit 7 just fine, but with 4 pH it says ER.
And there is not the checkmark next to pH, to say it completed.

I guess I will try 10 pH standard and see if that works.

Try soaking it in tap water for 24hours.



J

 

[Doer]

I did that. Followed all the instructions. It looks like you always start with 7 and then go to 4 or 10.

10 pH is all that is left without taking the battery out for a reset....if that will reset.

 

[budbro18]

the meter i had said to keep it in liquid that was a neutral ph. And mine has a manual calibration screw so idk if that has anything to do with it holding up better than one that runs its own calibration?

 

[aisach]

The attached publication from Orion is a great resource. This was one of my bibles when I was writing operating procedures for pH analysis, and writing training courses. So much info in there.
I caution though, that some of the instruments are expensive and require more attention than most growers are willing to spend. But the theory and instructional info can be for everyone.

The .pdf file is too large to put on the forum so I hope this link works for you.

http://www.thermoscientific.com/ecomm/servlet/techresource?storeId=11152&langId=-1&taxonomy=4&resourceId=91832&contentType=User+Manuals+[Water+Analysis]&productId=12769470

Try the cleaning solution followed by a rest period in storage solution for a day or night. Again it depends on the frequency of use. If used daily clean once a week or two. If used heavily throughout the day, be strict about the weekly cleaning.

 

[aisach]

the meter i had said to keep it in liquid that was a neutral ph. And mine has a manual calibration screw so idk if that has anything to do with it holding up better than one that runs its own calibration?

They all crap out at some point. If you happen to get a good one...great.

 

[EZmooover]

pH Testing
A little background on it. pH is the function of hydrogen. A gaseous element.

Correction... pH is the logarithmic function of the hydronium ion => H3O+ , also known as protonated water. It is not a function of the gaseous element hydrogen.

*Written in the spirit of accuracy and truth. Cause that's what we want on RIU.* Carry on...

 

[aisach]

Yeh, I kinda glazed over that part a bit, I have to admit.
Didn't want to risk my students falling asleep, if you catch my drift. They just wanted to hit the lab and play with the meters. LOL

 

[aisach]

DOER

Tri Meter
Looks like the probes are replaceable.



So I just watched a you tube video of a guy calibrating this meter you mentioned. I was horrified at his technique. But the steps he was performing seemed to be correct. IMHO

He made 3 errors that we teach people not to do when working with a glass electrode.
1. He banged the thing on the sides of the glass beaker.
a. NEVER do that. Stir the electrode GENTLY. Or get a stand for the probe, or a stir plate and a magnetic stir bar. They are awesome btw.
2. He didn’t stir the sample, instead he stirred for a second then dropped the probe into the bottom of the beaker and let it sit.
a. Always stir the sample.
b. Don’t let the probe touch anything.
3. He WIPED the probe. And rubbed on it.
a. Dab the probe with a lint free cloth. Try not to wipe, rub the electrode.

And also….rinse the probe with RO or DI water in between each solution. A yogurt container could be used as a rinse beaker. And a measuring cup to pour the water on. Or get a squeeze rinse bottle. And dab off the drop.

Always use fresh portions of cal solutions. Don’t reuse them. Keep them cool.

Dry connections.
Put the connectors in a baggie with a couple packs of dessicant (cheap on Amazon).

From the manufacturer:

Q:	Why are PPM, TDS, pH and EC important?
A:	PPM and TDS are abbreviations that represent the concentration of elements in a solution or atmosphere. PPM is short for parts per million and TDS for total dissolved solids. EC (electro conductivity) is another form of measurement for TDS. PH is a measure of acidity or alkalinity which dictates plant uptake of particular elements.

Q:	My pH meter doesn't hold calibration. How often should I recalibrate it?
A:	pH meters do need to be calibrated by the user every day since the membrane does change and is affected by the temperature as well. If pH values are very critical then it will need to be recalibrated several times a day, or before each sample test (depending on how critical the value is). Uncontaminated calibration solution is very important as well. For each calibration, pour some solution in a separate container. Keep out of sunlight and away from heat.

Q:	What is the suggested pH range for my hydroponic system and soil plants?
A:	Hydroponic and soil gardens differ in the fact they both need different pH ranges for nutrients to be made available for plant absorption. Maintain a pH between 5.0 and 6.5 for hydroponic gardens and 6.0 to 7.0 for soil applications.