pH meter

[red-beard]

I just switched to a pH meter, about a week ago. About $40 on Amazon, and I only picked up the 1 place past the decimal unit.

A few notes since I started using it.

This one came with a 2 point calibration and 2 calibration standards. The directions are pretty good on how to calibrate. It tells you when to stick it in the standards. You do it, press the button and move to the next one.

Main operation. 1 button to turn on. Fill the cap with pool water to line. Place the meter in the cap and shake to get the air out. Stand on its end. Wait for the pH reading to stabilize. Whole process takes about 10 seconds. Throw away sample and turn off probe. Rinse the cap and probe with distilled water. I fill the cap and swirl the distilled water in the probe. You are supposed to leave the probe wet. Recap.

My eyes can't read the color changes above 7.6. This makes it easy.

 

[Jimrahbe]

Red,

This is my problem.. "Wait for the pH reading to stabilize".. I've bought two pH meters (different from yours) but cost about the same and they never "stabilize" They just keep changing...

Would sure like to find one that works for me...

Sigh!!

Thanks,

Jim R.

 

[red-beard]

Are you shaking it to get the air bubbles out?

 

[Jimrahbe]

Red,

It has been a while since I used them, but I don't remember shaking anything...

How long does it take for yours to stabilize??

Thanks,

Jim R.

 

[mgtfp]

I've got the PH60 from Apera. Reading takes about 2-3 min to stabilise, longer when not stored in storage solution. I liked being able to just replace the sensor in the PH60. Once I started using it, I realised that the two digits of the PH60 help a lot when waiting for the reading to stabilise, even though the two digits are not really required for our purposes.

I have the same problem with colours above 7.6, even 7.4 is a challenge. Especially now in winter when keeping pH in the upper range, the colour test is hopeless for me.

 

[red-beard]

Red,

It has been a while since I used them, but I don't remember shaking anything...

How long does it take for yours to stabilize??

Thanks,

Jim R.

Maybe 10-15 seconds at the most. If you don't shake the probe, there is an air bubble in the measuring area.

 

[DanF]

I bought the PH60 a few weeks ago after realizing I couldn't accurately match colors using the comparator. i am happy with it so far.

This one came with a 2 point calibration and 2 calibration standards. The directions are pretty good on how to calibrate. It tells you when to stick it in the standards. You do it, press the button and move to the next one.

It seems that, for testing pool water ONLY, you dont have to calibrate using the 4 pH or 10 pH standards, only the 7. Another member contacted Apera about this. Saves a little time.

They opened a 'ticket' for me and then, after answering my question, closed it. Apparently the ticket is purged afterward, unfortunately.
The answer to the question was yes, calibration with the 4.0 or 10.0 solution is unnecessary for measurement in the 7s/8s. Calibration with the 7.0 solution is good for 7.0+/-2.0.

Curious about storage - Do you store the tester with distilled water in the cap, or just leave it a little wet?

 

[mgtfp]

As far as I understand, you shouldn't store it with distilled water. Either KCl storage solution or a drop of tap water in the cap.

 

[red-beard]

I "rinse" the probe by putting a "test sample" of distilled water, shaking and then throwing the sample out. I shake water out of the probe, but leave it wet and re-cap. I do this after I turn the probe off.

I'll try doing the single point calibration.

Why would tap water be better than distilled? I test every day. I just want the pool water off the probe. I'll re-read the engrish directions.

 

[DanF]

Why would tap water be better than distilled?

Agree. I would think that distilled would be better than tap, since they have you rinse in distilled.

I'll re-read the engrish directions.

LOL. Make sure you read (like I did not) that you can re-use the calibration fluid. I dumped mine the first two times I calibrated and now I need to buy more.

 

[Jimbarstow]

Mine stabilizes in about 10 seconds. I store upright in KCl solution and rinse with distilled water then shake dry before using. Mine has a little icon that comes on when it has reached a stable reading. I calibrated it recently and it was still right on. I’d be wary of not doing a full calibration (including low and high points). Big deviations in pH are what you must catch for the health of the pool (and swimmers).

 

[red-beard]

I pulled the directions for the PH20 (my model). Under section 6, you are supposed to rinse the unit before and after measurement with distilled water. It has a note to not STORE the probe in distilled water. I take this as: "don't keep the cap filled with distilled water". I rinse and shake off excess, both unit and cap, then close it up.

Under section 4, it talks about the KCl solution. It is used if the probe dries out and you cannot get a stabile reading. It suggests overnight soaking in 3M KCL (SKU: AI1107).

 

[Bama Rambler]

FYI, the reason you don't want to store it filled with distilled water is because it will draw the potassium chloride solution (KCL) out of the reference cell and cause inaccurate readings. The reason they recommend soaking it in KCL if the cell drys out is to replenish the solution in the reference cell.

 

[mgtfp]

The manual of the PH60 states that storage in purified water will cause permanent damage to the probe, due to the reason explained by Dave. If it just dries out, you can refresh with KCl solution, but distilled water does more to it than just drying out.

There was an extra note with my PH60, saying that a few drops of water were added to maintain the sensitivity of the probe. Together with the statement above I assume that these drops were just tap water.

In my case, the stabilization really takes about 2 min. After 30 sec the drift is quite slow, but it still keeps drifting. I usually put the tester in my sample first, do the titrations, and then take the pH reading.

Since I started waiting at least 2 min, the readings are very consistent, I see the daily drift due to CO2 out-gassing, and get a good extrapolation when I have to add acid again. The pH changes after adding acid are also spot on (I use Chem Geek's spreadsheet for the calculations).

Part of the drift in my case could also be the water temperature, it's winter here, water has about 8C at the moment. When taking the sample inside, the small amount in the test tube will of course warm slowly up. Let's see what summer temperatures will bring. I might run a test by holding the probe straight into the pool.