PH meter recommendations?

[gkardmw]

Hi,

I want to buy a pH meter as I mix my own developers and would like to note the pH while mixing in the alkali. When I was a teacher, I had a lot of bad experiences with pH meters losing calibration and a class set giving wildly different readings. Can anyone suggest a good meter that is not too expensive? Thanks!

 

[runswithsizzers]

I'm afraid not much has changed. If you want to be able to trust the results, you are going to need to spend a fair bit of time fooling around with calibrators.

What is the range of values you want to measure, and how much resolution and accuracy do you need?

 

[albada]

I recently purchased an Oakton pH 100 which is doing fine so far. It's a middle model which should be fine for working with developers.
@runswithsizzers is correct: The probe must be calibrated periodically, so you must get some pH 7 and pH 10 buffer solutions.

I keep three beakers containing some distilled water at all times, making it convenient to clean the probe before and after making measurements. To clean the probe, I dip it in the three beakers in succession, similar to Ilford's wash method for film and RC paper.

Mark

 

[gkardmw]

Something like a pH of 6 to 10 I should think would do it.

Yeah, I use to do a 2 point calibration using buffered solutions of pH of 4 and 10 and checked it with a buffered pH 7 solution. Had to do it almost every time I used them. The pH values would often appear to drift over even short periods of time. I used some pretty expensive older boxy models (I don't recall the brands), some cheap units meant for the students, Vernier probes... they all acted the same. I kept the probes moist and in an anti-fungal agent.

I see members here arguing over small amounts of developer components and dismiss the effect of whether the reagent is hydrated when anhydrous components are required. And no one seems to consider how accurate and precise are their balances and their techniques ... I suppose if they are consistent, it won't matter to them but when communicating these quantities to others, it might very well matter as their techniques and equipment might differ greatly.

Anyhow, it is all in fun and probably good enough.

Oakton pH 100? I will have to check that out.

 

[mshchem]

I used pH meters in the 1980's . Get a couple buffer solutions to calibrate the meter.

 

[albada]

Something like a pH of 6 to 10 I should think would do it.

Yeah, I use to do a 2 point calibration using buffered solutions of pH of 4 and 10 and checked it with a buffered pH 7 solution. Had to do it almost every time I used them. The pH values would often appear to drift over even short periods of time. I used some pretty expensive older boxy models (I don't recall the brands), some cheap units meant for the students, Vernier probes... they all acted the same. I kept the probes moist and in an anti-fungal agent.

I see members here arguing over small amounts of developer components and dismiss the effect of whether the reagent is hydrated when anhydrous components are required. And no one seems to consider how accurate and precise are their balances and their techniques ... I suppose if they are consistent, it won't matter to them but when communicating these quantities to others, it might very well matter as their techniques and equipment might differ greatly.

Anyhow, it is all in fun and probably good enough.

Oakton pH 100? I will have to check that out.

The Oakton pH 100 can be calibrated with one, two, or three points. I use only two -- 7 and 10 -- because developers seldom go below 7.8. The third point would be pH 4, but I don't bother with it. It sounds like you will go below 7, so you will want that third point. I use a no-name buffer-kit selling for about $20-25 on amazon.
Any decent meter should support at least three points; I suggest avoiding a two-point unit.

Mark

 

[Mick Fagan]

I started using Hanna pH pocket meters in 1987 (roughly) at the time they were perfect for what I was doing, these days their range of pocket pH meters is nothing short of brilliant.

I can also vouch that they are waterproof as I've dropped my current one twice into solution, rinsed it off and continued on. I used them extensively in the 1980's to roughly 2007 for colour film chemistry, C41 and E6.

I don't have this model, mine is around 10 years old and two point, but this model could be the go for you. That price is AUD.

pHep®5 pH/Temperature Tester with 0.01 pH resolution and 3 pt. calibration

Hanna's pHep®5 is an advanced, ergonomic, waterproof pH and temperature tester, with 0.01 resolution, that measures from -2.0 to 16.0 pH pH and accuracy of ±0.05 pH. pHep5 features automatic one or two-point calibration to known buffer and automatic temperature compensation. Waterproof...

hannainst.com.au

 

[bernard_L]

IMO it is essential to store the sensor dipped in a saturated solution of KCl potassium chloride). Even my cheapo pH meter behaves better since I that. If you don't, the head will degrade.

 

[Pentacon_777]

I managed to find industrial pH meter. It is Great Lakes Instruments model 570P. pH Meter is dismantled from old control panel and was going to recycling. This one probably works it was on the self about only three years. I can have two more meters of same model but working is maybe more so so but for art least spare parts okay. I found also original manual from old archive file and figured probably how to do wiring. Next I will order sensing glass and reference electrodes and 300ohm NTC thermistor for temperature compensation.

 

[Alan Johnson]

I use 3 point calibration [it's a curve] with 5% sodium carbonate anh pH = 11.6

Sodium Carbonate

Sodium Carbonate | Na2CO3 or CNa2O3 | CID 10340 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more.

pubchem.ncbi.nlm.nih.gov