Pocket pH tester update

[setsailsoon]

Folks,

Many of you may recall I have a fairly common (in men) color blindness that affects my ability to discern shades of red so I use a digital pocket tester for pH instead of the red/orange ph color drop test. I've been doing this a couple of years now and have some things I've learned to pass along:

• Batteries last about one year of 3 times/week testing.
• When readings get erratic or seem to be drifting upward you probably need new batteries or to make sure there's no corrosion on the contacts.
• Calibrate monthly with standard solution you can buy online under $10. Buy a smaller bottle as it will last you longer than it's shelf life.
• After calibration rinse the electrodes thoroughly in the tap and be careful not to get water above the electrodes on the end.
• I put the cap on wet (don't shake it off). Better life will be achieved if you put a sponge soaked with KCl storage solution. You can buy this on Amazon also around $10.
• Be sure to turn it off after use, it can run down the battery much quicker if you forget.
• These all seem to be made by the same couple of manufacturers, be sure to get ATC (automatic temp calibration). Even with this feature they are only around $15. So far mine is over 2 years old and still going fine.
• Make sure you let the meter fully stabilize... it may look like the reading has stopped changing but wait a minute or two. It often can change another .5 pH unit.
• After use, rinse the tip with tap water (never distilled water) and store it wet with the cap firmly.
• Never allow the tip to dry out! The cap fits tightly to ensure less evaporation.

I hope this helps.

Chris

 

[bobandsherry]

Where did you buy and what brand/model?

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[pooldv]

Very helpful, thanks for posting. I bought one late last year to use this year because I also struggle with the shades of red. I think I bought a Dr Meter with ATC.

 

[setsailsoon]

Thanks for the replies and I'm glad this is helpful.

The meter I bought was Dr. Meter ATC. I bought it and pH 7.0 calibration solution on Amazon.

Chris

 

[miles267]

Which Dr. Meter specifically? There are multiple on Amazon. Now I'd like one as red shades starting to look the same [emoji3]


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[pooldv]

Mine is Dr Meter PH 002.

 

[camueller]

I just got me a ph meter off amazon recently in order to aid me in my vinegar and kombucha making adventures that I've recently gotten into. I think the brand is ETEK or something alone those lines, but it looks just like pooldv's above (case and all), and others I see on amazon. It came with calibration solutions so that was nice. It cost less than $15 and I thought I'd try it when I get back into full swing testing my pool water. So far I've just been testing my tap water and the water from my reverse osmosis filter. It seems accurate and the results are consistent from test to test, so it seems like it's working ok. I appreciate this report of first hand experience as I learn to use this new device. I don't have any color blindness issues or anything, but sticking a meter into a solution sounds easier than drops when I just want a quick check.

 

[JoyfulNoise]

I have nothing against using a digital pH probe. If that's what you want to do to make water testing easier (and fun), then go for it. I will post this info for those thinking about in hopes of staving off an unnecessary purchase (assuming one has normal vision) -

If you feel the colors of red/yellow are too hard to distinguish, try these steps first -

1. Use 4 drops instead of 5 drops of the R-0004. There's nothing magical about 5 exact drops. The drop count sets the intensity of the color not the actual color hue itself. So sometimes using one less drop helps to make the shades more distinguishable.

2. Do the test outdoors and in bright daylight with a solid neutral to white color background. I have deck chairs with a white mesh on them that is perfect for holding the comparator up to. As always, back to the sun with the comparator block held out at arms length...try not to squint and force your eye's to see a color.

3. On the Taylor #9056 block, I use my index and middle finger to block out the color swatches above and below the ones I';m looking at. Believe it or not, with the color swatches close together like that, your eye and brain will work against you as the brain will sometimes blend the colors together. You eyes don't focus on one color but the entire visual field and so there's a tendency to lose less pertinent "information" (like color hue) to maximize visual distinction (just in case there's a tiger in the pool area looking to eat you).

4. When all else fails, ask your spouse! My wife has much better color matching capabilities than I do - as is evidenced by the sad state of fashion my children go to school in when I'm responsible for dressing them. So sometimes it's best to ask for help.

If nothing else works, then get a pH probe...

 

[setsailsoon]

I have nothing against using a digital pH probe. If that's what you want to do to make water testing easier (and fun), then go for it. I will post this info for those thinking about in hopes of staving off an unnecessary purchase (assuming one has normal vision) -

If you feel the colors of red/yellow are too hard to distinguish, try these steps first -

1. Use 4 drops instead of 5 drops of the R-0004. There's nothing magical about 5 exact drops. The drop count sets the intensity of the color not the actual color hue itself. So sometimes using one less drop helps to make the shades more distinguishable.

2. Do the test outdoors and in bright daylight with a solid neutral to white color background. I have deck chairs with a white mesh on them that is perfect for holding the comparator up to. As always, back to the sun with the comparator block held out at arms length...try not to squint and force your eye's to see a color.

3. On the Taylor #9056 block, I use my index and middle finger to block out the color swatches above and below the ones I';m looking at. Believe it or not, with the color swatches close together like that, your eye and brain will work against you as the brain will sometimes blend the colors together. You eyes don't focus on one color but the entire visual field and so there's a tendency to lose less pertinent "information" (like color hue) to maximize visual distinction (just in case there's a tiger in the pool area looking to eat you).

4. When all else fails, ask your spouse! My wife has much better color matching capabilities than I do - as is evidenced by the sad state of fashion my children go to school in when I'm responsible for dressing them. So sometimes it's best to ask for help.

If nothing else works, then get a pH probe...

Matt,

Great ideas, thanks so much! They may help others not as color-blind as me. When she's available I usually resort to #4. My concern is that when I've checked it seems I usually read the test high. I can't discern any difference between about 7.8 and 8.2. Usually I want to call it at least 8 which requires MA addition. But if I do a verification check with the meter (freshly calibrated), ph paper, and the wife the reading is 7.6-7.7 which in my case needs no acid.

One additional point to make on the digital meters. Be sure to let it finish the reading. This often takes 3 mins or so. It may look like it's stabilizing then it will slowly climb as much as .5 pH units.

Best regards,

Chris

 

[miles267]

Was watching a YouTube video earlier on this Dr Meter pH 002. Said it's inexpensive since it's only calibrated to read water at 77F? Is that true?


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[pooldv]

Not the one with ATC, Automatic Temperature Control.

 

[setsailsoon]

Folks,

I've done a fair amount of research on pH testers. They are actually fascinating devices and there's interesting electro-chemistry plus material science involved. Below is a summary of how they work plus a few additional and important tips:

These units have two electrodes that contain KCL buffer and are sealed. You can see the tip of each, one is glass (called the measurement electrode) and the other is ceramic (called the reference electrode). The glass tip actually contains a very small amount of metal (usually lithium) so it can actually conduct electricity and it is ultra thin so H+ ions can pass through it... this gets to how they work. Once submerged the ions are attracted to each other on each side of the very thin metal infused glass. This results in a voltage between the glass and the other electrode called the reference electrode. This voltage takes some time to stabilize as the charged ions all match up with each other at the inside and outside of the ultra thin metal infused glass layer. More expensive units have thinner glass so the voltage stabilizes more quickly but they are also much easier to break. The voltage is directly related to the ph of the solution measured and varies somewhat with temperature. The voltages are tiny in the range of a couple hundred milivolts. There is a very thin silver wire attached to the inside of each electrode and these are attached to a circuit that converts the voltage to pH and temperature compensates it (on the ATC versions) then displays it on the LED readout. As I said earlier the electrodes are sealed. As the unit is used tiny amounts of charged ions actually migrate across the thin glass wall and contaminate the KCL solution. Calibration solves this problem for a while but eventually renders the probe unusable. Some of the cheaper units like the Dr. Meter indicate you can do at least 365 measurements before excessive KCL contamination destroys the unit. But information on this is scant. I will calibrate monthly or so and when I notice it's off by greater amounts it's probably a good time to replace it. There are very high quality units that have replaceable probes and even refillable probes that you can drain and replace the KCL solution but these are $100+. I'd rather just replace mine every couple of years. One of the best ways to extend the life of the unit is to store it properly with the following practices:

• Rinse the tip with tap water (never distilled water) and store it wet with the cap firmly on to prevent it drying out. The cap fits tightly to ensure less evaporation.
• If you want to extend the life of your probe get some KCL storage solution (Amazon ~$12) and put some on a small sponge that you insert inside the cap.

I'll edit my original post to add these tips.

There are a couple of low priced units just like the Dr Meter that appear to be identical. Also, a few have appeared on the market that have an auto calibrate feature. I'll be trying these and provide updates in the future.

I hope this helps and isn't more than you ever wanted to know about digital pH measurement.

Chris

 

[JoyfulNoise]

In the chemistry lab, we always kept our probes submerged in a cap full of KCl solution. We could typically get 18 months to 2 years out of a probe before needing to change it. These were industrial type probes that plugged into a separate meter, not a monolithic unit. I would expect the retail grade ones to not last as long.


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[camueller]

very interesting and helpful information, thank you both!

I'm curious though, why shouldn't you rinse the probes in distilled water?

 

[AUSpool]

I'm curious though, why shouldn't you rinse the probes in distilled water?

Bit of a guess really but I'm thinking that distilled or deionised is not ionically balanced with the KCl in the probe. KCl in the probe will try to migrate out of the probe and into the distilled water, shortening the life of the probe. The instructions for the Milwaukee PH55 says to add a couple of drops of the storage solution or pH7 calibration buffer to the cap for storage.

If buying one of these I would always go for a two point calibration meter over a single point calibration meter and I would use pH7 and 10 calibration buffer solutions.

Sounds obvious but never risk contamination and calibrate in the calibration solution bottle. Decant into a small glass shot glass for calibration and discard after use. I would rinse first with a little solution too.

Choose carefully and know the limitations. Going back to the Milwaukee PH55, it has a range of 2.0 - 16.0 and an accuracy of +/- 0.1 which when applied means a reading of 7.8 could be anywhere between 7.7 and 7.9. For around $11 more from eseason gear the PH56 has a range of 2.00 - 16.00 (the second decimal point is significant) and an accuracy of 0.05 meaning the same reading of 7.8 could be anywhere between 7.75 and 7.85. Well worth the extra $11 for me.

 

[Patrick_B]

I would like to know why they say it has a range up to 16. I've dealt with most of the quality pH sensors in existence and never seen that.

 

[pooldv]

Weird, doesn't the PH scale end at 14? Typo?

Check, just googled that to be extra sure. The pH scale goes from 0 to 14.

 

[bobandsherry]

Choose carefully and know the limitations. Going back to the Milwaukee PH55, it has a range of 2.0 - 16.0 and an accuracy of +/- 0.1 which when applied means a reading of 7.8 could be anywhere between 7.7 and 7.9.

I'm sure my match the color test with Taylor kit will vary even more than that, especially at 7.8-8.0+ range. I think variance of +/-1 is pretty reasonable and wouldn't really impact your overall pool maintenance.

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[Patrick_B]

Weird, doesn't the PH scale end at 14? Typo?

Check, just googled that to be extra sure. The pH scale goes from 0 to 14.

Exactly...

 

[JoyfulNoise]

pH can go below 0 and above 14. For concentrated solutions of sodium hydroxide, the concentration of OH- can exceed 1 molar. So, the pH can go as high as 15.75. Remember that the standard pH range of 0 to 14 that everyone is familiar with is what is defined by water's equilibrium constant (1x10^-14) and is a measure of the ratio of the thermodynamic activities (denoted "a") of dihydrogen oxide (H2O) to the product of hydronium activity (H+) and hydroxide activity (OH-). Activity is proportional to concentration. When concentrations exceed 1 molar, then the pH can go above 14 or below 0. Another example is muriatic acid - at 20 Baume the concentration of HCl is 34.45% which makes the hydronium (H+) concentration greater than 1M. This means the pH is less than 0 or approximately -1.


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