pH Calibration
- Thread starter EricJC
- Start date
EricJC
New member
While I probably know the answer to this:
pH prior to calibration ranging daily between 8.27 & 8.39
pH at time of calibration by two different chemical test kits reading 8.4
AC now reading pH of 7.63...have recalibrated several times, opened new bottles of 7 & 10 Coralife Calibration Solution.
Suggestions?
Thanks, E.
pH prior to calibration ranging daily between 8.27 & 8.39
pH at time of calibration by two different chemical test kits reading 8.4
AC now reading pH of 7.63...have recalibrated several times, opened new bottles of 7 & 10 Coralife Calibration Solution.
Suggestions?
Thanks, E.
Personally, I don't like bottles of calibration solution, as after their first use the CO2 in air will cause the values to change (especially the 10.0 solution). This probably isn't your problem, but I do recommend single use packets.
If this is a Pro unit are you putting the temperature and pH probes in the calibration solution? What number values are displayed on the bottom of the screen in each calibration solution? After calibration with the controller in the run display does it read 7 in the 7 cal sol. and 10 in the 10 cal sol.?
Curt
If this is a Pro unit are you putting the temperature and pH probes in the calibration solution? What number values are displayed on the bottom of the screen in each calibration solution? After calibration with the controller in the run display does it read 7 in the 7 cal sol. and 10 in the 10 cal sol.?
Curt
EricJC
New member
Curt,
Purchased and received your single dose packages of 7 and 10 calibration fluids. I've just re-calibrated the AC3Pro obtaining the following "settling" results: 7.0 fluid settled to 7.49, 10.0 fluid settled to 10.52. After calibration, the AC reads 7.0 in the 7 and 10.0 in the 10. After placing the probes (temp+pH) back in my sump, pH reads 8.0. Two separate chemical tests put the pH between 8.3 and 8.4...suggestions?
Thanks,
Eric
Purchased and received your single dose packages of 7 and 10 calibration fluids. I've just re-calibrated the AC3Pro obtaining the following "settling" results: 7.0 fluid settled to 7.49, 10.0 fluid settled to 10.52. After calibration, the AC reads 7.0 in the 7 and 10.0 in the 10. After placing the probes (temp+pH) back in my sump, pH reads 8.0. Two separate chemical tests put the pH between 8.3 and 8.4...suggestions?
Thanks,
Eric
I would certainly be a lot more confident in the value the AquaController reports rather than the color matching kits. It sounds like it is properly calibrated. What is the alkalinity of your tank? What is the high and low pH of your tank over 24 hours?
I don't know if this is the case with your tank or not, but the color matching test kits are very inaccurate, and some are purposely skewed to read values higher than reality. Many tanks have pHs that run about 8.0 to 8.1 (especially Ca reactor tanks), but the books say the pH should be about 8.3. So the manufacturers skewed the pH tests to read .2 or .3 units too high. That way the user gets the results he is looking for, and continues to buy pH cal test X. Even if the tests are accurate you can easily get .2 pH variation in the reading depending on what type of lights (Sun, florescent, etc) you take the reading with.
Curt
I don't know if this is the case with your tank or not, but the color matching test kits are very inaccurate, and some are purposely skewed to read values higher than reality. Many tanks have pHs that run about 8.0 to 8.1 (especially Ca reactor tanks), but the books say the pH should be about 8.3. So the manufacturers skewed the pH tests to read .2 or .3 units too high. That way the user gets the results he is looking for, and continues to buy pH cal test X. Even if the tests are accurate you can easily get .2 pH variation in the reading depending on what type of lights (Sun, florescent, etc) you take the reading with.
Curt
I'd possibly look for a different brand of calibration fluid. I tested some in this article, and some can be way off:
A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm
This article may also be useful:
Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm
A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm
This article may also be useful:
Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm
