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Discussion Starter · #1 ·
Hello:

I bought a pinpoint PH moniter used and am trying to calibrate it. I cannot seem to get the numbers to 7 or 10 while calibrating the unit. I have the probe in the solution and am cranking the appropriate screw to adjust the display and no matter how far I turn the screw it will not reach PH 10 or 7 without adjusting the wrong screw. Does this meen that the probe is bad? Does anyone know where to buy good probes for these units for less than 50 bucks? Would home depo sell these probes?

Thanks for the help.

Jay
 

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I've got the REEF rash!
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You cal. to either 7 or 10 not both.and only a fish(aquarium) type of store would have them cataloge is your better bet on new probe.
 

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Tang Lover
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so are you saying that when you stick the probe in the 7.0 solution, you can't get it to read 7. and when you stick it in the 10.0 solution, you can't get it to read 10?

If so, I'd say you got a bad monitor. Take it back.
 

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Discussion Starter · #4 ·
Thats right skeety. When I put the probe in the 7.0 solution and attempt to calibrate the 7. screw I have to turn the screw many many times to get it near 7. Sometimes I can turn it 5 complete revolutions and the moniter will only move mabey from 9.5 to 9.0 for example. Then I will rince the probe in tap water and try to calibrate to the 10 solution the moniter may read 7.5 and I begin to turn the 10 screw and the moniter will move to mabey 8.8 then stop there no matter how many revolutions on the screw I adjust.

Does this sound like a bad moniter or a bad probe. I bought all this by trading a skimmer and cash for the probe, a Knopp C Calcium Reactor with co2 tank and regulator but had to buy a new pump for the reactor. He threw in the PH Moniter but said it does work but needs calibtared. He gave me the solution packages but the probe was not stored wet, it was dry and exposed.

What do you think? Can I run my Reactor without a moniter? Not a good idea probably but 50 bucks for a probe is a little expensive to. Mabey I should just buy a new moniter with probe.

Jay
 

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Im not sure...i wuold be more inclined to think probe.......either way....it is one or the other...............Do you iknow anyone else with a monitor?????

One way to figure it out is to try to calibrate it with someone elses monitor. Someone mentioned the other day that the probes can simply be refilled sometimes instead of replaced...........

i dont think that storing the probes dry damages them....it just throws the calibration off.............

If it DOES damage them.........ive got one being damaged as wwe speak.......:arg:
 

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Discussion Starter · #7 ·
I think so. It has a small glass ball at the end. Looks right.

I can bring it into the LFS and he said he will calibrate it for me for 5 bucks. Then I will know if its the probe.

Jay

Jay
 

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Jay357 said:
...When I put the probe in the 7.0 solution and attempt to calibrate the 7. screw I have to turn the screw many many times to get it near 7. Sometimes I can turn it 5 complete revolutions and the moniter will only move mabey from 9.5 to 9.0 for example. Then I will rinse the probe in tap water and try to calibrate to the 10 solution the monitor may read 7.5 and I begin to turn the 10 screw and the moniter will move to maybe 8.8 then stop there no matter how many revolutions on the screw I adjust.

Does this sound like a bad moniter or a bad probe? ...He gave me the solution packages but the probe was not stored wet, it was dry and exposed.

What do you think? Can I run my Reactor without a moniter? Not a good idea probably but 50 bucks for a probe is a little expensive, too. Maybe I should just buy a new moniter with probe...
hmmm... something is not right with this, Jay, I think you need to tell us exactly what you're doing when you attempt to calibrate, making sure tht you test the correct set point with the correct solution. When you put the probe into the calibrating buffer for the 7.000, it should initially read 7.xxx, NOT 10.XXX or anything close to 10. I've included a link to the correct process for calibration below.

Before doing anything else, buy some 20 mule team borax and use a pint of distilled or RO/DI water (473ml) and add a half teaspoon (1/2 level tsp.) of 20 Mule Team Borax to make a resultant pH standard solution with 2 gm of sodium metaborate per 473 ml or 4.3 grams of sodium metborate/litre. Mix well. Although using this method to make the standard will only result in an accuracy of about plus or minus 10% of the lab standard sodium metaborate pH calibration solution, there is such a weak dependence of pH on concentration of the solute buffer here that it is close enough for our purposes. To use this solution to check your probe, bring a freshly made batch of borax solution to aquarium temp and immerse the probe into the solution, allowing 5 minutes for final probe measurement. The meter should show a value of 9.19 + 0.02 pH units. For this particular set of conditions where the probe has been allowed to dry out, try soaking the probe tip in distilled water for a few days before testing. If your value with the meter is not within range, cleaning and recalibration of the probe are definitely indicated, if not the immediate replacement of the probe. If after cleaning and recalibrating the probe with known fresh good standards your meter/probe still cannot pass this test, then it is time to have the meter tested against a known good meter with probe combination, and failing this comparison, then replacing either the probe or the entire pH meter setup.

Sorry to be the bearer of bad news, but if the meter is not accurate, it will do more harm than good for your setup.

You CAN run the CO2 reactor without a meter, but maintaining adequate pH and avoiding excessive CO2 in the water will be difficult to do, and if CO2 gets too far out of line, then it can be toxic to your fishes and drive pH so low in the system that your corals will not be capable of skeletogenesis, and other calcifying organisms may not be capable of forming test, shells, etc. If you're going to use a CO2 reactor, it becomes very important to meter your CO2 correctly, and although it is not absolutely necessary to have a CONTROLLER, you will need at least a systemic pH monitor that you can rely on to adjust your bubble rates for appropriate CO2 metering.

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 so long as it stays wet with at least ASW, although it WILL prolong the useful life of the probe if you use KCl.

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. If allowed to completely dry out, you've pretty much lost the probe.


HTH you get up and running.
 

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Discussion Starter · #9 ·
Wow...Thanks Tom. Sounds like you know all about how these things work. I will check out the links you provided and start my probe soaking today, I have a RO/DI unit so I have good water to soak it in. I did not know about using Borax to make a standard PH solution for testing.

Jay
 

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Discussion Starter · #10 ·
Looking at the probe I can see liquid inside. Fluid appears to be somewhat cloudy or has some debris in it.

Jay
 

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Jay357 said:
Looking at the probe I can see liquid inside. Fluid appears to be somewhat cloudy or has some debris in it.

Jay
soak it for a few days in RO/DI, then test it. I have a meter that I dropped into the prop tank (don't ask... :rolleyes) that has a good probe, if yours is AFU'd, drop me a PM and maybe we can talk.
 

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Jay357 said:
He gave me the solution packages but the probe was not stored wet, it was dry and exposed.
Jay
Not good. Probe is probably ruined. Try Tom's advice first...and if that doesn't work, I'd recommend a new probe. But before you waste the money, maybe see if someone you know has a probe you can borrow just to make sure it's NOT the monitor itself.
 

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Just curious, have you tested the probe arfter re-hydrating the device?
 
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