PinPoint pH Probe won't calibrate ??

[ShirleyM]

Hello,

I have a PinPoint pH probe and replaced the probe about a year ago. It operates, but it won't calibrate. I can get the 7.0 solution to calibrate, then have to turn the screw really far to calibrate the 10.0 solution, then the 7.0 is way off, and so on. Usually turning the screw just a tiny bit makes a big difference, but I'm having to turn the screw really far to get a big difference (like 8.5 down to 7.0)

Is the probe bad, or the calibration unit? or the whole thing?

If so, what can I replace it with that won't wear out in a year?

Thanks so much,
Shirley

[rabeiler]

Silly question, but have you tried a fresh set of batteries? If you run it on AC, try running it on batteries.

Also, what type of calibration fluid are you using? The best kind is individually sealled packets that have expiration dates on them. Any of the bottles of fluids, etc tend to change PH as soon as they are opened. If you have had the fluid for a long time it might be the problem as well.

Couple of things to try. I have heard that Pinpoints are pretty good. I have not had any issues with mine yet.

Ross

[ShirleyM]

I'm using the individually sealed packets. I will try new batteries, but in the past it's always said Lo Bat or something like that on the screen.

Thanks,
I'll let you know...

[ldmk]

Another thought is to clean the probe ("bulb") itself with a soft bristle tooth brush. I've never had any problems with my Pinpoints (the one in my FWT is about two years old) and I agree that the problem may be with the calibration fluid.

Good luck.

K.M.

[inthesand]

be sure to use the packets from pinpoint and not Coralife's fluid.

[ShirleyM]

We are...and thanks, and I will do all the testing and battery changing tomorrow (Sunday) --- ran out of time today...
Thanks,

[Mr. Ono]

Your probe may have gone bad.

Is it in use constantly or just used for checking the pH now and then? If it is the later the probe may have dried out. If it is the prior then try cleaning the probe.

If you have fresh batteries and fresh solutions then it is the probe.

[tdwyatt]

If the probe is more than 18 months old, definitely replace it, at a year old iit is a bit on the short side, but possible. Depending on how old the main unit is, and where it was stored, the unit may need to be replaced. Try the battery replacements first, and try vacuumming out the unit just in case there is salt inside the unit. This still sounds like a probe issue to me, I think removing the mineral deposits and attempting to check the meter with borax would be needed before spending the $80 to $90 for a new meter. If you do buy a new one, use the old probe initially to check and see if this has been the problem. If the new meter with the old probe will calibrate, store the probe that came with the mew meter for use in a couple of years (keep the tip of the probe wet with the KCl storage solution provided)

The safest way to clean mineral deposits from your probe is to soak it in white vinegar for an hour or two, then rinse it in RO water and soak it for 10 more minutes in clean RO water and calibrate. It will help to remove the biofilm from it as well. To do this, put 1 tablespoonful of Chlorox (Sodium hypochlorite solution-household bleach) in a clean glass container and dilute it with 9 more tablespoonsful of RO water. Soak for 10 minutes, the rinse in clean RO water and soak for 10 more minutes. Recalibrate.

To recalibrate the Pinpoint meter and probe, use the little packets of standards, they are much more reliable when opened fresh and in date than the bottles of standards (which start to wander from the exact pH of the standard as soon as they are opened). Before opening the packets of standardizing solution, bring them to tank temp (throw the unopened packets in the sump for a bit, about 10 minutes). Get a ceramic mug for each standard to test, and put it in the sump as well. When ready to test, both the mug and the standards will be at tank temp. Open the 7.0 pH packet at the top only, put it (upright) in a water bath in the mug (this prevents temperature change induced variations), then put the probe into the standard solution and stir it gently. Set a timer for 10 minutes, then check the reading at the end of that period and adjust the reading to the standard's pH (7.00). Rinse the probe with fresh RO water, then shake any excess water off the probe and place it in the 10 or the 4 pH standard, and set the timer for 10 minutes. At the end of that time, adjust the reading on the meter to the pH of that solution, rinse in RO water, shake off any excess water, and retest the 7.0 standard again for 2 or 3 minutes. It should read to within 0.01 pH units of 7.00. If not, repeat the calibration process. If it passes the retest, rinse the probe and put it into service.

If this doesn't fix the problem, repost and I will make other suggestions. Hope this helps.

[ShirleyM]

Wow! Thank you Tom for such a detailed answer!

I never got to test it yesterday...will do so today.

I have always had it in the tank and I know not to let it dry out.

I've not used the tank water in the cup method...I always had placed the packets in a short glass (like a rocks glass) with the tip snipped off, and kept the fluid inside the packets. I rinsed with tap water and shook off inbetween, and I didn't leave it a full 10 minutes, but as soon as the numbers quit moving, I started adjusting.

I will clean it per your instructions, and follow through and let you know later on. It's less than 18 mos old...seems I got the new probe last summer or fall.

Thanks!

Shirley

[RWD]

Probe question here. Are ph probes totally submersible? Or will it damage the probe?
Bob

[ShirleyM]

Mine have always been totally submersed...I've had two over the past 4 yrs...
??

[N38MD]

I know Pinpoint PH probes are epoxy sealed and can be completely submirged.

Ron

[tdwyatt]

Yes on submersible, Interesting, I have two (don't ask why ) that are both at least 4 years old, never chnged the probe, and have been in continuous use with BATTERIES (that seem to last about 6 weeks in the meter) for the entire time. Both are withing plus or minus 0.02 units of each other, and although I clean and calibrate then about every 9 to 12 months (in the winter usually), I have never changed the probes (I think I bought one of them used from Bill Esposito WAY back). They are in a cryptic sump and really don't get any light whatsoever. I just bought a new one with an ac adapter from a friend in PA while they are on sale this month. I have planned to put it into service in the new display, I am thinking that I may leave the a/c converter in the box and continue to use batteries, this might just be the trick for these meters... (no spikes)

[ShirleyM]

My PinPoint pH probe is WORKING!!

Thank you for the instructions!

~ Shirley

[Casey]

Shirley what was it?