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uber-stupid
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4,781 Posts
Discussion Starter #1
I have a pinpoint PH monitor and a pinpoint PH controller. One of my probes reads correctly when it is hooked up to either meter but one of my probes will only read between 6.5 and 7.2 PH no matter what the PH of the solution is. The one that is not reading correctly was on the controller on my calcium reactor. When I placed it in there it was working fine. It is only about 3 months old. I cleaned it with fresh water and a tooth brush a month ago and it was still working correctly. I cannot calibrate my meter with it either it just maxes out at 7.2 in the 10PH solution and the 20 mule team borax solution. However it will read the 7 solution correctly once I calibrated it to 7 for that solution but when I try to calibrate it to the 10 solution it makes it read 7.2 in the 10 solution and the 7 solution. I don't know what else to do with it.

Any help here would be appreaciated.
 

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The Muddy Mod
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7,007 Posts
Is there any warranty period on these things?
 

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uber-stupid
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4,781 Posts
Discussion Starter #3
I got this one from dr. fosters I think. I will have to look back on my paypal account and see .
 

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Registered
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37 Posts
Lemon Juice for 30 min, if that doesn't working dip into boiling water for 5-10 min. If both don't work I usally find that nothing else fixes them (Ie trash it).
 

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uber-stupid
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4,781 Posts
Discussion Starter #5
Just soak it in lemon juice for 30 mins? Any lemon Juice?
 

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Premium Member
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17,355 Posts
I do not recommend either lemon juice or boiling the probe as a fix for the issues with the probe. If cleaning the probe of biofilms with dilute chlorox, and then soaking it in white vinegar (so you dont get the organics as you would with either brown vinegar or lemon juice) to remove Ca deposits doesn't allow it to pass testing with borax solution, then either the glass tip of the probe has a crack/leak, or the KCl solution in the probe has leaked out through another seam to the extent that the electric potential cannot be established to make the pH meter read the pH. Boiiling will increase the interenal pressure of the probe, driving out more KCl solution, so this will actually make the issue worse.


The probes at the hobbyist level are not intended to be refilled as some top-end ($$$) probes are, so there is really nothing to do once you're sure that the meter itself is not at fault but to replace the probe. Try to test the meter by using a known good probe before discarding the probe in question. If allowed to dry completely out during storage, these probes will malfunction as well, so make sure to save the plastic tip the units come with for storage outside the aquarium water. Ideally you will want to use a solution of KCl to store the tip, but it is not ABSOLUTELY NECESSARY, although it WILL prolong the useful life of the probe.

see The Borax test here , and see THIS POST LINK to clean and calibrate your pH probe correctly . I do not recommend using a toothbrush to do vigorous cleaning on pH probes, as this may damage the selectivity of the probe tip to ions (it'll ruin it). Only use a toothbrush to very lightly remove any gross organic material, if at all. The tips are specially made to be very selective and allow for ionics to move across without losing all the KCl quickly. The meter works by creating a small electric gradient across the tip, and the pH is measured as a function of the electric current generated by this differential. This is why it is crutial to estabish both the center of the pH gradient (the 7.000 buffer) and the slope of the difference between the center and 3 pH units out either way (with either the 4.000 or the 10.000 buffer solution). The meter uses these values to determine what the pH values of a tested solution are once the calibration is complete and the probe is functioning correctly.


HTH
 

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uber-stupid
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4,781 Posts
Discussion Starter #8
Thats not what I wanted to hear Tom. I think it is junk. I will contact the place where I purchased it (either MRC or Dr. Fosters) to see about a replacment probe.
 
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