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pH meters

alanrockwood

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Can anyone recommend a good, very inexpensive pH meter? Ideally it should have a range of 0-14 pH units with two decimal point readout. Alternatively, a one decimal point readout would be fine.

Also, how about calibration of the devices?

I have used pH meters, but they were expensive laboratory grade devices. I would like something for home use, including darkroom applications.

Thanks.
 
Whether used for hobby or commerce, a electronic pH-meter needs

-) good choice of its electrode (depending on the resp. medium)
-) care for the electrode
 
I use HANNA meters. I have two. Easy to use, accurate and easy to replace the electrode.

PE
 
  • AgX
  • Deleted
Hanna offers the whole range: pocket meters ("testers") as that above and classic meters.

Hanna's counterpart to that above costs (here) exactly 10-times as much.
 
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I too have one of the HANNA pH meters. Due to having very reduced sensitivity in my hands, meaning I don't have much feeling for what I'm holding, I often drop things.

After destroying one HANNA pH meter by dunking it in liquid, I picked up their waterproof pocket pH meter; I can vouch that it is waterproof.

https://hannainst.com/hi98128-phep-ph-tester.html

Mick.
 
That is the one I referred to.
 
This thread might be better under color processing. In decades of B&W work I have never had the need for a pH meter.
 
I use the pH-108,which fulfills your specs and is very easy to calibrate.
 
Gerald C Koch said:
This thread might be better under color processing. In decades of B&W work I have never had the need for a pH meter.
Click to expand...
My desire to get a pH meter relates to a desire to do some developer development or modification.
 
RalphLambrecht said:
I use the pH-108,which fulfills your specs and is very easy to calibrate.
Click to expand...
It does not fulfill the OP's reqirements as its accuracy is 10-times worse. (I refer to a requirement of a 2-digit readout and the resp.accuracy.)


Of course, when the OP states to be sufficient with a 1-digit readout the whole discussion is fruitless.
He then even might consider high-sensitive ph-strips.
 
AgX said:
Of course, when the OP states to be sufficient with a 1-digit readout the whole discussion is fruitless.
He then even might consider high-sensitive ph-strips.
Click to expand...

Actually, what I said was one decimal place readout could work, not one digit. Your right that if it were one digit pH strips would be good enough, and a lot cheaper too.
 
Sorry, with digits I meant those decimal places behind the comma.
And there are strips with a resolution of 0.2ph (I do not know of their accuracy)

On the other hand there are ph-meters with a display of 0.00pH but a accuracy of only 0.1 (the same as with some thermometers)
Ralph got such one.

With considerating a meter of any kind one has to ask oneself what accuracy one needs.

With ph meters one has to consider the additional costs as the calibration buffers, and on long term the storing buffer (some meters got throwaway gel-filled caps, other fluid refillable ones) Such meter is nothing to buy for "in case" as one may do with a clinical thermometer.
 
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I have a Denver Instrument Basic PH meter that I bought it from medical surplus for under $50 with electrode, instructions, everything.
Search eBay for any of the brands of PH meters mentioned here, seems to always have a boat load of them.

Recommend you get fresh buffer solutions for calibration, and some distilled water to keep probes clean.
 
But do not use destilled water for keeping, but only the advised keeping sdolution. Also some manufacturer advise to clean the electrodes with tap- not destilled-water.
 
AgX said:
But do not use destilled water for keeping, but only the advised keeping sdolution. Also some manufacturer advise to clean the electrodes with tap- not destilled-water.
Click to expand...

That is important advise. The problem with the cheap $10 all in one test stick style pH meters is that you actually can't keep the electrode in a storage solution. Maybe the quoted one from Hanna is different there.

I'd recommend a unit with external probe. They are easier to handle and the probes come with a storage tube that is filled with KCl solution.

Another thing for us photographers to keep in mind is that most pH probes must not be used with solutions that contain more than small amounts of Silver ions. The reference electrode in the probe is a Ag/AgCl element immersed in KCl. Maybe Ag+ in the measured solution will precipitate in the porous junction connecting the KCl with the outside.

The maker of my equipment used to have a special probe with KCl and KNO3 electrolyte (probably inner and outer electrolyte with an extra junction in between), which was offered for use in photographic labs. It could be used with Ag+ loaded solutions. But I guess that is another victim of the implosion of the film market.

Monitoring the pH of increasingly used fixer is not advisable for that reason. I do wonder about used colour developer, though. I'd expect it not to wash out any Silver from film/paper. Does anyone know for sure if I'm right? What about rehalogenating bleach?
 
Combined glass electrodes (with internal Ag/AgCl reference electrode) must be stored in the same KCl solution that its filled (usually 3.5 M KCl). Between the measurements its can be stored in plain distilled water for a short time.
 
Those "pocketable" meters typically have caps filled with storing KCl solution (might be messy if non-attentive, but
cheep to fill up again), or caps filled with a KCl gel (practical, but would need complete, filled spare caps to substitute if necessary).

lantau said:
Another thing for us photographers to keep in mind is that most pH probes must not be used with solutions that contain more than small amounts of Silver ions.
Click to expand...
I tried to hint at that in post #2. But even PE did not reply on this point.

So again, one should know in advance what to meter, and at what precision,
 
Alright, I'll reply. For silver solutions, we use a silver electrode for one pole, and a double junction silver electrode for the other pole. Best results are obtained with a KNO3 salt bridge. The silver electrode is used bare or is plated with the halide ion used in the solution.

PE
 
In any case, I wonder what to expect from a meter (as hinted at by the OP) that costs 1/8 or so of the price of meters with similar specifications and seemingly built of other brands.

(We had similar discussions on cameras...)
 
No good idea, as the internal resistance of a VOM (=multimeter) likely will be too low for the requirements of such electrode circuit.
 
+1 to AgX
For the electrical and electrochemical reasons potential of glass electrode must be measured by a special circuit with high input impedance.
 
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