pH meter frustration

[G Bear]

Hey I have been using the Dr Meter pH pen throughout my first grow.

I just now recalibrated it and I am confused by the results. The calibration went successfully but afterwards I tested the distilled water expecting a neutral result. It kept dropping all the way down to 5.9 before I gave up. It probably would have gone lower.

So this pH pen is total crap, right?

 

[xtsho]

Your pen is likely just fine. You can't trust distilled water to be neutral and your pen can't read the pH in distilled water accurately. Calibrate with calibration solution and then test your nutrient solution. Ignore any reading you get with distilled water.

Pure distilled water should be neutral with a pH of 7, but because it absorbs carbon dioxide from the atmosphere, it's actually slightly acidic with a pH of 5.8.

What Is The pH Of Distilled Water?

The pH of distilled water immediately after distillation is 7, but within two hours after distillation, it has absorbed carbon dioxide from the atmosphere and become acidic with a pH of 5.8.

sciencing.com

pH electrodes will NOT give accurate pH values in distilled or deionized water because distilled and deionized water do not have enough ions present for the electrode to function properly. The readings will drift and be essentially meaningless. If you want to test the accuracy of your pH electrodes, use pH buffers.

Why doesn't my pH Sensor read pH 7 in distilled or deionized water? - Technical Information Library

pH electrodes will NOT give accurate pH values in distilled or deionized water because distilled and deionized water do not have enough ions present for...

www.vernier.com

The electrodes of a pH meter will not give accurate values in pure water because distilled and deionised water do not have enough ions for the electrode to function accurately. The readings will most likely fluctuate and be meaningless. For calibration purposes, pH buffer solution is the best way to test your pH electrodes because it has a defined and accurate pH. General tap water normally has enough ions present to allow a pH electrode to function correctly. Because of this, tap water is a good short term 24hr solution for storage.

The Science Behind the pH of Distilled Water

The most discussed question in the science group is about the pH of Distilled water. This blog can debunk some of the questions behind it.

www.westlab.com

 

[G Bear]

Your pen is likely just fine. You can't trust distilled water to be neutral and your pen can't read the pH in distilled water accurately. Calibrate with calibration solution and then test your nutrient solution. Ignore any reading you get with distilled water.

Pure distilled water should be neutral with a pH of 7, but because it absorbs carbon dioxide from the atmosphere, it's actually slightly acidic with a pH of 5.8.

What Is The pH Of Distilled Water?

The pH of distilled water immediately after distillation is 7, but within two hours after distillation, it has absorbed carbon dioxide from the atmosphere and become acidic with a pH of 5.8.

sciencing.com

pH electrodes will NOT give accurate pH values in distilled or deionized water because distilled and deionized water do not have enough ions present for the electrode to function properly. The readings will drift and be essentially meaningless. If you want to test the accuracy of your pH electrodes, use pH buffers.

Why doesn't my pH Sensor read pH 7 in distilled or deionized water? - Technical Information Library

pH electrodes will NOT give accurate pH values in distilled or deionized water because distilled and deionized water do not have enough ions present for...

www.vernier.com

The electrodes of a pH meter will not give accurate values in pure water because distilled and deionised water do not have enough ions for the electrode to function accurately. The readings will most likely fluctuate and be meaningless. For calibration purposes, pH buffer solution is the best way to test your pH electrodes because it has a defined and accurate pH. General tap water normally has enough ions present to allow a pH electrode to function correctly. Because of this, tap water is a good short term 24hr solution for storage.

The Science Behind the pH of Distilled Water

The most discussed question in the science group is about the pH of Distilled water. This blog can debunk some of the questions behind it.

www.westlab.com

Thanks a lot. Appreciate it.

Im about to calibrate again because I think I made a mistake during calibration. Between calibrations I was rinsing in the same cup of distilled water. Was also using the same container for each test solution. Perhaps that threw it off? Or more likely I am overthinking it. Still gonna recalibrate and avoid contaminating the test solutions etc. Thanks again.

 

[Doug Dawson]

Thanks a lot. Appreciate it.

Im about to calibrate again because I think I made a mistake during calibration. Between calibrations I was rinsing in the same cup of distilled water. Was also using the same container for each test solution. Perhaps that threw it off? Or more likely I am overthinking it. Still gonna recalibrate and avoid contaminating the test solutions etc. Thanks again.

Hey I have been using the Dr Meter pH pen throughout my first grow.

I just now recalibrated it and I am confused by the results. The calibration went successfully but afterwards I tested the distilled water expecting a neutral result. It kept dropping all the way down to 5.9 before I gave up. It probably would have gone lower.

So this pH pen is total crap, right?

I like to double check every so often with drops to verify my PH pen, I also use a Dr. Meter. I am not a fan of the calibration of the unit using 3 solutions of strange value but when calibrated it does seem to work well. I would buy some drops as a backup to the digital pen as they are a very good tool to double check results.

 

[G Bear]

That was a great answer. Again, thanks. Im just gonna test the pen now in the solutions as you suggested.

 

[Jerry Tyson]

@G Bear is on point. I like to use the drops as a double check to my pen every few times just to confirm accuracy. Obviously drops don't go out to 2 decimal places

 

[G Bear]

Ok I just tested each pH solution and this pen does seem accurate. Thanks for the help. Glad I didn’t immediately buy another pen. I am impulsive.

 

[MickFoster]

Never wrong and needs no calibration.......I've been using the drops for over 25 years without issue.

 

[G Bear]

View attachment 4585181
Never wrong and needs no calibration.......I've been using the drops for over 25 years without issue.

I do have a liquid test kit for my fish tanks...but the kit is like 14 years old and past the expiration date on the bottles. Not sure if they’re still accurate or not but I may as well grab a new kit just for pH. this one tests ammonia, nitrates, nitrites, pH, etc.