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View Full Version : Anyone have wildly fluctuation in pH occasionly?


aculross
10/03/2011, 10:53 AM
Every now and then I have some wild fluctionations in my pH - look at this data log from this AM

DateTime Temp pH Temp2 (not used)

06:00 10/03/2011 78.2 8.00 21.4
06:10 10/03/2011 78.2 7.99 21.7
06:20 10/03/2011 78.2 7.99 21.8
06:30 10/03/2011 78.2 7.99 21.4
06:40 10/03/2011 78.2 7.98 21.8
06:50 10/03/2011 78.2 7.98 21.5
07:00 10/03/2011 78.2 7.97 21.4
07:10 10/03/2011 78.2 7.97 21.4
07:20 10/03/2011 78.2 7.96 21.6
07:30 10/03/2011 78.2 7.95 21.5
07:40 10/03/2011 78.2 7.29 21.4
07:50 10/03/2011 78.2 7.30 21.6

Notice the pH between 7:30 and 7:40 - I'm not even sure if it is possible in reality for the pH to go down this much in 10 minutes. The probe is not new but in general give consistent readings except for these cases - Anyone have any ideas what may be going on?

RussM
10/03/2011, 11:12 AM
Does anything turn on at about 7:30? Strangeness like this is often related to interference or electrical leakage in the water.

Go into Configuration->Probe setup, select the unused temp probe, and just disable it.

aculross
10/03/2011, 11:20 AM
Nothing comes on/off at 7:30 - This is an ApexJr with a PM1 on it. I actually only use 2 of the outlets for fans and heaters at the moment - the other two are unused (but active actually - meaing they have code against them but nothing pluged into the outlets). Thanks for the tip on disabling the second temp probe. I did that.

Any other ideas?

aquamanic
10/03/2011, 12:40 PM
put the probe in a cup of tank water and monitor that for 24 hours. See if the spurious readings stop. If they do, then as Russ says you've got something leaking current in the tank.

You can try cleaning the probe. If the reference junction gets clogged it can cause funny voltage (i.e. pH) readings although normally they don't return to correct, they just get worse and worse.

Re-route the probe cable so it's laying on your floor, away from everything. Again, monitor for stability.

Mostly it's a process of elimination until you find the culprit.

aculross
10/03/2011, 01:05 PM
Is this a sign of a probe starting to go bad? Like I mentioned, it's not new.

aquamanic
10/03/2011, 02:12 PM
Could be. See my second point above. If it gets worse and worse then that's what it is. You can try soaking in vinegar for a couple of hours then gently brushing with a soft toothbrush. Then re-calibrate. That may help.

Thing is these probes, especially pH will wear out. The coatings on the glass membrane and the porus reference junction are just not built for more than a year or so of use. But it could be other things also which is why you have a couple of possibilities to eliminate.

aculross
10/03/2011, 05:38 PM
OK, thanks everyone. Went home and clean the probe off with a soft toothbrush. pH went up from 7.7 to 8.3 almost immediately. So next question, how often do you clean your pH probe?

aquamanic
10/03/2011, 06:10 PM
as often as it needs it :D

really, I think it varies by tank. Every couple of weeks?

Watch yours though. If the pH drops again quickly over the next few days then you probably have a aging probe and you'll need to think about replacing it.

schwaggs
10/03/2011, 09:51 PM
Are you running any float switches? I had similar problems with a defective float switch that was shorting the signal wires to tank water.

bamf25
10/03/2011, 10:19 PM
I had this on my apex lite. The ph probe was stuck at the highest for like 1 week then it suddenly started reading again. Since then it has worked perfect. On the plus side I have a free backup ph probe now.

aculross
10/04/2011, 10:20 AM
Thanks everyone - seems to be OK today - I do have a float switch but agree that the probe probably just needs replacing.