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pH meter problems again! HELP!

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69ron

69ron

Rising Star
I'm having pH meter problems again!

I hate this. All the pH meters I have seem to get the same problem after a while. They become extremely erratic.

I have gone through dozens now. All end with the same problem. Here's the symptoms:

Read: pH meter shows 14, then 0, then 3, the 8, then 2, etc., etc., etc.

Shake pH meter: pH meter looks fine for a minute or two, then back to showing erratic numbers.

What causes this problem?

Why does shaking the meter temporarily fix the problem?

How can I fix this or do I just have to buy another one?

These are all very expensive Hanna meters by the way in the price range of $100-$500 that have developed this problem.

I've had this same problem with so many now, I'm so sick of it.
 
Is it the kind of meter where you can change out the pH detection element?
I don't think that's the correct term for it, but the head on the meter, some of the expensive ones can have the head replaced.
Have you tried that? Probably a dumb ??, but that's where I'd start.

I've also read somewhere...this was a while ago, when I was learning to use a pH meter, so I could be off a bit here...that you can either store the removable heads in a buffer solution to keep them true.(?)
Or soak a pH meter in buffer solution over night to clean it.
(please check those suggestions out before doing them, to make sure I remember correctly!!)


Cheers,

WS
 
Problems with pH meters are invariably the probe electrode end. Of course they need to be nicely cleaned when used (distilled water). They often need to be re-calibrated; and they often need to be replaced. Even in university labs, pH meters are a source of frustration.

Wikipedia as an informative and short article on the pleasures and miseries of the digital pH meter.
 
warrensaged said:
Is it the kind of meter where you can change out the pH detection element?
I don't think that's the correct term for it, but the head on the meter, some of the expensive ones can have the head replaced.
Have you tried that? Probably a dumb ??, but that's where I'd start.

I've also read somewhere...this was a while ago, when I was learning to use a pH meter, so I could be off a bit here...that you can either store the removable heads in a buffer solution to keep them true.(?)
Or soak a pH meter in buffer solution over night to clean it.
(please check those suggestions out before doing them, to make sure I remember correctly!!)


Cheers,

WS
Click to expand...

Yeah it's the removable kind. The correct term is probe. The probes keep going bad and I keep having to replace them. The probes themselves are pricey. I’ve tried all kinds from all different price ranges from el-cheapo to top of the line and all of them go bad in the same way. The other part works fine and has worked for many years now, it’s just the probes that are going bad.

The symptom is the same, they go from working perfectly to suddenly going bonkers. For example, I measure a solution at pH 5.4, it works for a while. I keep mixing the solution with the probe in the solution and then suddenly it goes bonkers giving readings that are completely random from one end of the pH spectrum to the next. Cleaning doesn’t solve the problem, but vigorously shaking the probe does, but only for a few minutes and it then goes back to it’s crazy readings again. It’s almost like there's a short in the wire in the probe and shaking it causes it to reconnect.

This has happened to every single pH probe.

I’ve had some show this problem after a week of use! And others last for a few years and then start showing this problem.

Is there something that can cause this that maybe I’m doing wrong with the meter? What can cause it to go from reading fine, to being random, and then back to being fine after vigorously shaking it? Sometimes shaking it works for a few days, other times just a few seconds and its all bonkers again.

Does anyone else have any experience with this problem and know of any solutions or does this just mean the probe it end of life and beyond fixing?

These probes are the kind that are refillable. Would refilling it make any difference?
 
69ron said:
Is there something that can cause this that maybe I’m doing wrong with the meter?
Click to expand...

Probes really are supposed to be used in a "dip/clean/return to storage solution" manner. They aren't supposed to stay in an unknown solution for a long time. The storage solution is typically supposed to be at pH 3, I believe. If you were to leave a probe in a solution far from that for a long time, it would likely at least lose calibration.

(the above was true, at least, ten years ago. I haven't really used pH meters much since then).
 
I clean them and do all the normal maintenance they need. They are stored in proper storage solution designed specifically for them.

The most they're in a solution that I'm reading the pH of is maybe a few minutes and then they are returned back to their storage solution.

This problem has nothing to do with calibration. They are properly calibrated and go back to being properly calibrated after a vigorous shake.
 
69ron said:
I clean them and do all the normal maintenance they need. They are stored in proper storage solution designed specifically for them.

The most they're in a solution that I'm reading the pH of is maybe a few minutes and then they are returned back to their storage solution.

This problem has nothing to do with calibration. They are properly calibrated and go back to being properly calibrated after a vigorous shake.
Click to expand...

I can only say that they've been somewhat of a pain in many labs. Most people just accept that the probes have to get changed fairly regularly.

OK, one thought (don't hold me to this). Don't the probes actually have a tiny hole in them (or some sort of semi-permeable area)? Maybe you're getting some crystalization (or some other clog--minute particles of bark), and when you shake it the hole clears up. Maybe they all get better if you shake them; I wouldn't know because I've only ever seen people replace them immediately when they go whacky.
 
SWIM uses a cheapo hydroponics digital meter that he has had for about 4 years and it still gives good results, just needs recalibrating every now and again. Swim also found that lab meters were a bit erratic when he was at University so therefore reasons this is due to the tolerances of the lab equipment i.e a small scratch on the probe would send the meter way off.
 
Ya know, my $30 generic pH meter has been pretty damn accurate for over a year now.

Don't the probes actually have a tiny hole in them (or some sort of semi-permeable area)?
Click to expand...

Is that how it works??
I must have studied that little glass tip for over an hour one time, trying to figure out how pH meters read anything through the glass bulb!!

Do you know anything else about how they use a glass bulb to read pH levels?
Kind of interesting!

WS
 
Wikipedia has a quick and easy article about pH meters, and a link in that article to "glass electrodes," which explains how they work. Yeah, they are permeable in one area.

I've seen pH probes get KCL precipitated on them or around them--in their "storage solution." Seems to me if you got some gunk like that on the permeable area (usually a bit above the actual tip--on the side), then it wouldn't work--and vigorously shaking MIGHT temporarily cure the problem. That's total speculation, though.
 
Solute and respect to DMT-Nexus Community! This place and people have been a tremendous source of knowledge and inspiration for me in search for an “ultimate truth” we all seek. For past few years I was devoted lurker of this site. I am grateful for everything I found here but feel kind of guilty for not even showing up here once to say thanks or give something back.

Problems with pH meters are invariably the probe electrode end.
Click to expand...
“SWIMfriend” s remark is very true. A lot of careful maintenance is needed on electrode probe part of PH meter units. The PH meter itself does not need to be calibrated often. It is only done by labs maybe like once a year when they send the units back to manufacturer for recertification. For the type of experimentation we do it is not that critical at all and of course far from being economically feasible. The obviously easiest way to check Ph meter for at least a relevant accuracy is to plug in a calibrated, working electrode probe of right kind. That is why the best technique (when affordable-) is to have 2 channel PH meter with 2 probes connected which enables you to notice obvious deviations between the two in readings of the same sample. If there is no spare electrode available you can run a simple and generally reliable meter test. From Ph mode reading turn to MV mode. Disconnect the probe and short out the meter with shorting strap. It should read 0.0mv which is = pH 7.0. If it is out of range for more than -+2 the meter should be electronically calibrated by manufacturer. Too bad. If electrode is suspected to be faulty fallowing can be done. Try measure MV with pH buffer 7.0. The reading should be 0.0mv no more than +-20mv. Also with pH 4.0 or 7.0 it should read between 160-180mv. If off by more than +-12 of 177mv – too bad. The probe should be replaced or you can try reconditioning. Reconditioning can include such techniques as unblocking clogged junctions, checking for its crystallization and changing filling solution, cleaning glass membrane. There are tons of articles on how to on the net. One of the good sources is fishersci.com look up the section with technical documentation in pdf on electrode maintenance. OR coleparmer.com/techinfo/TechInfo_ByProduct.asp?ProdID=3527 (Product Maintenance section). In your case Ron, I would simply try to shake out the solution and refill it (which I bet you already tried). Accidentally scratched glass membrane would also contribute to your collection of dead probes. Avoid putting any kind of electric devices close to ph meter and especially electrode cable. Regular combination probes do not tolerate organic solutions very well – double junction electrodes or at least non-refillable (cheaper) are probably best for our kind of work. And unfortunately, yes there is always a place for a mystery with this kind of highly sensitive apparatus when you not operating out of state of the modern art laboratory.-) All the best everyone.
 
69ron said:
How can I fix this or do I just have to buy another one?

These are all very expensive Hanna meters by the way in the price range of $100-$500 that have developed this problem.

I've had this same problem with so many now, I'm so sick of it.
Click to expand...

It's generally accepted in the cannabis growing community that pH meters (and especially the probes themselves) are fidgety. While the meters most growers use is probably slightly less expensive, a bunch of them do splurge on the more expensive meters (including meters by Hanna). Complaints are frequent of having to change probes often and of meters simply going haywire and not taking accurate readings. I have found that storing my probe in some 4.01 or 7.01 calibration solution, and frequently rinsing it between readings with either of the solutions helps to keep it operational. I also have to calibrate it when it seems to be giving unexpected results. But, in general, I've found it's easier to use pH paper for my purposes.
 
I had my meter freak out on the second use. Turns our when measuring high PH (in my case 13.4) the probe starts to react at levels over 10. Second time I used it would only range from -5 - +2.0. Rinsed it out really good and shook it and the next day it worked 0.1 out of calibration. I think I am going to return it and get papers...
 
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