PH Probe calibration

techrach · #1 08/25/2006, 09:33 PM

I bought a PH probe a few weeks ago. I read the instructions and calibrated as said. I dose kalk and my PH test kit reads 8.2 - 8.3 range and my probe reads 7.9 - 8.0. how do you know the probe is correct. I tested my kalk at 2 TBSP per gal and the probe read 12.65. any help would be greatly appreciated.

roons · #2 08/25/2006, 09:57 PM

did you use the 7 and 10 pinpoint fluid?

PatMayo · #3 08/26/2006, 12:57 AM

You most likely have high use of alk. I do in my tank. YOu can see the specs in my sig. I dose saturated kalk 24/7 and can't keep up with alkalinity and calcium. I can't put it in the tank fast enough. I dose in addition to the kalk Randys 2 part formula each day. I dose about 90 ml per day of alk the calk.

I need to get a dosing pump that pumps more and then add some fans to the tank to promote evaporation.

If you calibrated the probe correctly then I would trust the probe not your test strips if that's what you are using.

My PH runs on the low side as well 7.8 to 8.1 even with dosing kalk 24/7.

You may need some fresher air in the house.

Regards,

Pat

bertoni · #4 08/26/2006, 02:00 AM

12.65 is pretty good for that type of meter, I think. The pH should be about 12.47, if my memory is correct. One test you could do is the aeration test in this article:

http://www.reefkeeping.com/issues/2004-09/rhf/index.php

If the pH rises after treatment, I'd definitely trust the probe.

NORTHBAY(707) · #5 08/26/2006, 06:37 AM

You need to use the 7 and 10 pin point fluids to set the probe, I keep forgetting thier High PH range meter. Not the low range which you would use 4 and 7 pin point fliuds.

Later.

techrach · #6 08/26/2006, 07:51 AM

I did use the 10 and 7 fluid. I dose Kalk 24/7 and I have a fan that runs with the lights. I will give the aeration test a try. thanks for all the suggestions.
I live in a new house and there could be a build up of CO2. I could run my skimmer air tube up to the attic do you think this would help?

roons · #7 08/26/2006, 08:03 AM

i have low ph most of the year due to co2................7.7- 8.0 , when house is open its normal................8.2-8.4................i have slow coral growth, thems the breaks..................i used to run my skimmer hose outside, but in winter , condensation woyuld build up inside the tube and make my skimmer overflow, took me months to figure this out, thought i had a bad skimmer.............and you wont see a big difference doing this as the tank will still have c02 buildup...........................i think maybe mine changed .02 doing this

MCary · #8 08/26/2006, 08:08 AM

To answer your question. The way you tell if any lab equipment is correct is by running controls. You need to run the pH probe on a sample of known concentration. You could for example run the probe using the standards as samples and see if they read 7 and 10, but its best to have a control near to the value you want to measure. Something 8 to 8.5 would be ideal.

Where to get controls? Maybe you can google and find a lab supply catalog.

Mike

roons · #9 08/26/2006, 08:12 AM

id believe the probe b4 the test kit, ive been using the same pinpoint ph probe and monitor for 2 years, once a month i calibrate using 7 and 10 fluids, if it calibrates , i move on...........

MCary · #10 08/26/2006, 08:15 AM

You should still run a control once a week. Calibration on all ISE's drift.

roons · #11 08/26/2006, 08:37 AM

so your saying , if i put the probe in 7 calibration fluid and it reads 7 it may still not be correct? what would the purpose of the fluid be then? i have a feeling your getting deeper into this than need be...............

MCary · #12 08/26/2006, 08:56 AM

What you have done in that case is run a control, just as I stated. You put the probe in 7 fluid and it reads 7 then your fine. Running controls is just checking the reading. Calibration is adjusting to a reading. Once a week, if you can, its a good idea to put your probe into a known solution. The 7 calibrator would be fine for this, a solution close to what you want to measure would be ideal. Check the reading. If it says 7, then your fine. If it says 7.6 then you need to recalibrate. Standard laboratory practice. A good idea for the non-lab person who does not have confidence in his equipment.

Mike

DgenR8 · #13 08/26/2006, 09:08 AM

I find that single use packets of calibration fluid are a better way to go than the small bottle that you could use over and over. Each time that little bottle is opened, I believe that the fluid value is compromised a little more.

roons · #14 08/26/2006, 09:39 AM

that is true, the orp fluid is good for about an hour