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neoalchemist74
06/21/2010, 06:10 PM
I'm looking for ideas on what would cause a ph probe to have an extremely short lifespan(two months or less) I.E. water chemistry, equipment interfereance, stray voltage, sealers, glues, anything anyone can think of.

loudell
06/21/2010, 06:29 PM
Depends on the cause of the failure.
Do you know why it failed?

bertoni
06/21/2010, 07:16 PM
Also, was it used as a probe or as a monitor, i.e., was in the tank continuously?

neoalchemist74
06/21/2010, 09:12 PM
Also, was it used as a probe or as a monitor, i.e., was in the tank continuously? continuous use via controller. I start to get incorrect readings with any probe after about two months. They calibrate up properly but run a full tenth of a point low. I'll replace the probe, readings are back to normal.Two months later same deal. Ive got about five probes here I might try cleaning one with some dilute hydroflouric acid and then soaking it in potassium chloride to try to renew it, but if that does"nt work I believe the gel must be contaminated

loudell
06/22/2010, 07:33 AM
I guess I'm confused but if you can calibrate the probe; it works.
If you feel it is reading low and you have calibrated it; the calibration is the final word unless your fluids are no good.
A small amount of drift over months is normal and is counteracted by recalibration.

Boomer
06/22/2010, 08:06 AM
Who's and what kind, model, of pH probes are they.

They calibrate up properly but run a full tenth of a point low


And how is that ? You ref it against a new probe ? And who's pH ref sol ? Many are off and not correct

Is this probe in a high flow area, which can "suck" the ref sol out. This causes a shift in the ionic strength to the probe, which seawater has allot of, giving error readings, as the probe becomes more sensitive to seawater.

loudell
06/22/2010, 08:09 AM
High flow will shorten the life marginally and will slightly accelerate the amount of drift. That is the drift that one would normally see after 3 months you may see after one month but I think this is a user issue. We'll see.

neoalchemist74
06/22/2010, 09:58 AM
I don't belive this is a user issue.(my fault, although I'll likely turn out to be wrong, happens often enough.) I am under the impression(sourced by a couple of article I've read) that certain water chemistry and other envronmental factors can cause probes to read false prematurely which is the reason for this thread.
As far as my situation goes. Through my own concern about accuracy of calibration solutions I've only been calibrating recently with freshly ordered one time use Milwaukee 7 and 10 packets. allmy pprobes are gel filled non refillable thebrands are pinpoint, Milwaukee, Digital aquatics and Hanna. this drift torwards the LOW only happens in one of my three systems. If I replace a probe, new probe, calibrate it with new solution it will show expected values but graduallly decline if compared to anther meter on another system after a couple of months it will be off. I ve tried alot of differant combos beetween calibrating probes with differant meters and differant systems with cositant results. A probe when run in my 75 gal sps sys. will run low after two months. I'll replace the probe and go through whole thing again.

Boomer
06/22/2010, 02:02 PM
You are still not saying where you put the probe and what the water flow is there compared to say the other tanks.

I've only been calibrating recently with freshly ordered one time use Milwaukee 7 and 10 packets.

That really means nothing, although their 10 is right on the nose.

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm

neoalchemist74
06/22/2010, 04:26 PM
Sorry spaced that. The probe is not in a high flow area in either system. The skimmer effluent creats a little turbulance near it but thats all.
Thanks for the link I'll check it out.

bertoni
06/22/2010, 04:45 PM
Interesting. Just to make things clear enough that I can understand them, after two months, the probe will calibrate properly with the solutions, but then read an incorrectly low pH when in a saltwater environment? You are checking that by running it in another tank against another pH monitor? So they're both measuring saltwater, both have been calibrated recently, and they don't agree? Have you tried calibrating both simultaneously with the same batch of solutions? That shouldn't really be necessary, but the situation is a bit strange.

I might try testing the probe with a borax solution:

http://web.archive.org/web/20021015005420/www.animalnetwork.com/fish2/aqfm/2000/feb/bio/default.asp

The most common problem that seems to cause pH measurement problems with meters, aside from calibration, would be electrical interference, although some might argue against that.

neoalchemist74
06/22/2010, 06:00 PM
Interesting. Just to make things clear enough that I can understand them, after two months, the probe will calibrate properly with the solutions, but then read an incorrectly low pH when in a saltwater environment? You are checking that by running it in another tank against another pH monitor? So they're both measuring saltwater, both have been calibrated recently, and they don't agree? Have you tried calibrating both simultaneously with the same batch of solutions? That shouldn't really be necessary, but the situation is a bit strange.

I might try testing the probe with a borax solution:

http://web.archive.org/web/20021015005420/www.animalnetwork.com/fish2/aqfm/2000/feb/bio/default.asp

The most common problem that seems to cause pH measurement problems with meters, aside from calibration, would be electrical interference, although some might argue against that. I'm going to try the borax solution as soon as I get a chance. Heres the procedure I went through last week.
a) noticed PH running a little low for 5:00 pm.
b) rinsed probe w/ ro/di and started the calibration sequence on my controller.
c)opened a new pouch (recently ordered) of 10 my controller does the curve solution first (4or 10). and placed the probe inthe packet and clipped both in my probe holder so the bottom 1/4th of the packet is submerged in my sump to equilize temp with temp comp. setting on.
d) rinse w/di and repeat w/7 solution.
e)lock in settings rinse probe in di return probe to tank PH is reading 8.20ish(low for 5:00 in my system).
f) repeat steps a through e same results.
g) I happen to have a brand new probe, Hanna brand,so I repeat the exact same steps with the new probe w/ the same batch of solution ( new packets) PH value when I return the new probe is 8.45,calcium reactor had been turning on later because of lower PH reading which allowed ph to rise alittle high the daily usual is around 8.4 at that time right now at 6:00 its reading 8.42.

loudell
06/22/2010, 06:09 PM
I'm still having a difficult time getting my arms around the problem or even if there is a problem.
A small amount of drift over the course of months can be common and this phenomenon is cured by recalibration.
Maybe this situation is not user error but user expectation....

bertoni
06/22/2010, 06:36 PM
Okay, so the new probe read about 8.45, and the old probe read about 8.2? And those measurements were right after both were calibrated with the same batch of pH packets? Both probes calibrated properly and read about 0.25 units apart? Sorry to be so long-winded, but that's a bit strange to me.

neoalchemist74
06/22/2010, 06:39 PM
I'm still having a difficult time getting my arms around the problem or even if there is a problem.
A small amount of drift over the course of months can be common and this phenomenon is cured by recalibration.
Maybe this situation is not user error but user expectation....

the probe I just replaced was new in april and a differance of 2 tenths of a point is a problem for me. It means my calcium reactor will not start injecting co2 until late in the day this severely limits the the usefulness of my reactor. Also I top off w/kalk which can on some really dry days send my PH higher than I'd like. Nothing too dangerous but if my probe is running low and starts the co2 injection later I can easily get up to 8.5. If the probe is still giving a low value, 8.5 may really be 8.65.

loudell
06/22/2010, 06:41 PM
Would more frequent recalibration (maybe every 2-3-4 weeks) until recalibration is no longer necessary solve the problem?

neoalchemist74
06/22/2010, 06:49 PM
Okay, so the new probe read about 8.45, and the old probe read about 8.2? And those measurements were right after both were calibrated with the same batch of pH packets? Both probes calibrated properly and read about 0.25 units apart? Sorry to be so long-winded, but that's a bit strange to me.

I agree. This has been since last fall. The exact scenario,separated by about two months each time.The reason I ask about water chemistry is that I read an article by Stephan Goemann where he states in a short blurb that certain water chemistry can be harmful to probes but he doesn't elaborate.

neoalchemist74
06/22/2010, 06:51 PM
Would more frequent recalibration (maybe every 2-3-4 weeks) until recalibration is no longer necessary solve the problem?

Maybe, but right now I'm out of solution. Next I'll probably try a borax calibration

loudell
06/22/2010, 06:55 PM
Really no difference between using a borax or 10.00 fluid for slope. You will need a 7.00 as well.
I would think that if you recalibrate every week or two at some point you would be attempting the recalibration and it will not be necessary...
Just my 2 cents.

neoalchemist74
06/22/2010, 07:16 PM
Really no difference between using a borax or 10.00 fluid for slope. You will need a 7.00 as well.
I would think that if you recalibrate every week or two at some point you would be attempting the recalibration and it will not be necessary...
Just my 2 cents.

I'll try. As a matter of fact I believe I may have already done that at some point successfully. I'm just trying to figure out why its nessicary. Of the 5 probes I have (minus the new one) I trust my oldest one the most because its always been in my nano, never in the display more than a day and its like 4 years old!

loudell
06/22/2010, 07:19 PM
4 years old may be a new continuous use record. What type of probe is it?

neoalchemist74
06/22/2010, 07:22 PM
4 years old may be a new continuous use record. What type of probe is it?

Pinpoint American Marine, still calibrates fast but it drifts a little.

loudell
06/22/2010, 07:27 PM
Look on the wire that comes out of the probe for a piece of gray/white tape. What does it say on it exactly?

neoalchemist74
06/22/2010, 07:51 PM
jj4
57325255-003b

loudell
06/22/2010, 07:58 PM
That probe was manufactured in October 2004 and was probably sold within 2-3 months of that date.
If you have been using that probe for 4+ years then you have the record for continuous use.
If you can calibrate it; it still works....

neoalchemist74
06/22/2010, 08:23 PM
I just calibrated it the other day and its showing a solid 8.4 in my nano.

loudell
06/22/2010, 08:31 PM
You should check the calibration with 2 accurate fluids to be sure that it is still holding calibration. The fact that it gives you a number you like from your nano tank doesn't mean it still works well....

neoalchemist74
06/22/2010, 08:33 PM
:celeb3:how do you know that is a record and is it a record for that brand probe or others as well?:beer:

neoalchemist74
06/22/2010, 08:36 PM
You should check the calibration with 2 accurate fluids to be sure that it is still holding calibration. The fact that it gives you a number you like from your nano tank doesn't mean it still works well....

like I said I just calibrated last week,used the last of my good solution. But I'll order some more, the best I can get and check it.

loudell
06/22/2010, 08:39 PM
I can't speak for other probes. I know that brand well; I own the company.
Regarding calibration, the probe could go out of calibration rather quickly if it is near the end of it's useful life. Check it and let me know.....

neoalchemist74
06/22/2010, 08:43 PM
I just checked it against some 6 mo. old General Hydroponics 4.01 and7.0 and for the 4 its reading 4.09 and for the 7 its reading 6.99.

loudell
06/22/2010, 08:49 PM
OK..good luck.

neoalchemist74
06/22/2010, 08:56 PM
loudell... obviosly your the best man to ask what is the absolute best way to clean these probes. I'm a scientific glass blower and have access to any and all glass cleaning and etching tools and solutions? Maybe nitric acid full strenght followed by alchohol.

loudell
06/22/2010, 08:59 PM
Generally speaking cleaning something is really a function of what is it dirty with? For a saltwater aquarium a little white vinegar will do a fine job.

Boomer
06/23/2010, 11:27 AM
Well Neo, it looks like Lou has you all fixed up :) But just some warnings. Stay away from nasty solutions like Nitric Acid. Hydrofluoric acid is a non-no. Some alcohols, like isopropyl or ethanol can destroy a probe by dehydrataion and convert the ionic silver into elemental silver if left in the solution over night.



Detailed cleaning procedures and what and what not to do. With Warnings

http://www.ph-meter.info/pH-electrode

neoalchemist74
06/23/2010, 12:48 PM
Well Neo, it looks like Lou has you all fixed up :) But just some warnings. Stay away from nasty solutions like Nitric Acid. Hydrofluoric acid is a non-no. Some alcohols, like isopropyl or ethanol can destroy a probe by dehydrataion and convert the ionic silver into elemental silver if left in the solution over night.



Detailed cleaning procedures and what and what not to do. With Warnings

http://www.ph-meter.info/pH-electrode

yeah, even HF fumes would be a disaster. nitric will not attack glass but will, if given enough time disolve plastics and ahcohols may have a small enough molecule to pass through depending on each individual probe and acetone would definately pass through.
I still haven't gotten any ideas as to why probes have such a short life span in my system. I believe either something is clogging them or something in my water is getting in and contaminating the gel.