PH PinPoint Calibration

[lpkirby]

Question for the PH PinPoint Owners.

I am Calibrating the PH Controller with a 4.0 and a 7.0. When I finish, I check it with a 10.01. I must not be doing it right or my probe is going bad. It shows my PH is now 7.8 and when I use aAquarium Systems Ph Tester it says I am at 8.0 Is that .2 a big deal. Also when calibrating how many times do you go back and forth with the Calib and the Slope adjustment? It seems that I am going back and forth..

Thanks for any help

[kingsland]

I believe they recommend using the 7.0 and 10.0 calibration fluids for saltwater. Measure the temperature of the cal fluids before beginning and use the temperature compensation charts on the cal package to get an accurate reading. I usually use three cups, one per cal fluid and a cup of tap water. Place the probe in the upper limit cal fluid and turn the screw until you get a measurement of 10.0. Rinse the probe in the cup of water and try to get as much water off as possible before placing it in the 7.0 fluid. Turn the screw until you get a measurement of 7.0. Rinse the probe and place in the 10.0 cal fluid and repeat the whole process until you can go back and forth between the 10.0 fluid and the 7.0 fluid and get repeatable readings. It takes a bit of patience. Also, the probe bulb will tend to accumulate tiny animals and corraline algae. This tends to effect the readings at least it seemed to on mine. Its easy to clean, just remove the probe from the monitor and soak it in a cup of vinegar.

[lpkirby]

Thank you, The problem I have is I got my Calibration Fluid from the LFS and it was the bottles only no paperwork... So how important is the temp adjustment?

[bertoni]

That model seems to be temperature-compensated, based on the web site. If both meters have been calibrated recently, and with 4 and 7 pH liquids, I'm not sure which would be likely to be more correct. 7.8 is low enough to warrant a little attention, in my opinion. Cleaning the probe and recalibrating might be a good idea, though.

[lpkirby]

Thanks, Jonathan

I am looking and I do have some Milwaukee 10.01 that has the temp on the side, the 7 does not... If I am reading this correctly it say that at 80 degrees F then I should calibrate to about 9.99. Well see

Thanks again

[kingsland]

I ordered extra calibration fluids and an ac adapter directly from American Marine (the manufacturer of the monitor). The teperature compensations listed on the packages are as follows:

Temp 7.00 Cal 10.00 Cal

50 7.06 10.167
59 7.036 10.107
68 7.016 10.051
77 7.00 10.00
86 6.988 9.965

There are two additional temperature listed at 95 and 104 degrees F. Let me know if you need those. Measure the temperature of the calibration fluids and set the PH monitor the setting closest to the temperature settings above. I use the cal liquids and the rinse water at room temperature (about 72 degrees). From the chart you can do the math and get close to what a midrange reading should be if you are between the listed temperatures. Hope this helps.

[Boomer]

King

I'm have problems with you calibration procedures. They are very wrong. You put the probe in the pH 7 and turn the calibration screw until the meter reads 7.00. Rinse in RO or RO/DI or distilled water and then put in the pH 10 solution for seawater and turn the slope screw until it says 10.01. You are now done

From PinPoint

IV CALIBRATING THE pH METER SUBSYSTEM
This is a two-point calibration instrument therefore TWO different calibrations must always be used. A pH 7.00 fluid must be used to set the CALIB and a pH 10.00 or 4.00 fluid is used to set the slope.

COMPLETE INSTRUCTIONS:
Before you begin the calibration, you should disconnect the pumps or valves that you are controlling, because the pH electrode will be put into solutions with a pH that is probably far outside the controller limits you have established.
Before you begin, make sure that you have the pH calibration fluids, and some room temperature tap water to rinse the electrode between calibration solutions. You must have a #7.00 calibration solution, and another solution with either be higher or lower pH (typically 4 or 10). If you are doing this for the first time, read through these instructions once to determine what is required before you begin.
Set the display mode switch (far right) to the central position (read). The pH LED (lower left) should be illuminated.
Remove the plastic cap protecting the end of the electrode if you are doing this for the first time. If the electrode has already been in service you should note the condition of the electrode and clean it if required.
Rinse the electrode with room temperature tap water taking cares to remove any accumulated salt. Rinsing the electrode prevents you from carrying over contaminating substances into the calibration solutions. Gently shake the electrode to remove any clinging drops of water.
Immerse the tip (bottom 1 inch) of the electrode into the pH 7 calibration fluid. It is important to use the pH 7 solution first. Be sure that the tip of the probe is fully immersed in the calibration fluid for a stable and reliable result.
Keeping the glass bulb immersed, gently swirl the ends if the electrode in the calibration fluid until the pH reading stabilizes. If the electrode is in good condition, the reading should stabilize in a few seconds. If the electrode does not easily stabilize; this may be a sign that the electrode is in need of cleaning or should soon be replaced.
Adjust the CALIB screw to bring the displayed pH to about 7.00
Remove the electrode from the pH 7.0 calibration solution and rinse it with room temperature tap water. Gently shake the electrode to remove clinging drops of water.
Immerse the end of the electrode into either the low or high calibration fluid. Usually pH 4 or pH 10 is the most common. Swirl the end of the electrode in the fluid until you obtain a stable reading, then adjust the SLOPE screw until the display shows the value of your calibration fluid (typically 4.00 or 10.00).
Again, rinse the electrode with room temperature tap water and shake of any clinging drops.
Re-immerse the electrode in the pH 7 calibration solution and now repeat steps 6-7-8 until the display shows 7.00 in the pH 7 fluid and 4.00 or 10.00 in the other calibration fluid that you have selected.
Rinse the electrode and return it to service in your system. Remember that the sensitive glass bulb of the electrode must not be allowed to dry out. Use the clear plastic cap filled with storage fluid or pH 4 calibration fluid when not in use.

The pH calibration process is now complete.

More things to look at.

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

[dave168]

lpkirby, I just asked the same question not too long ago at different forumand here is the thread

http://archive.reefcentral.com/forum...hreadid=878516

good luck

[lpkirby]

Cool Thanks Dave

[Boomer]

Dave

I took a look If your meter will not go up to 10 there is something wrong with the probe

[kingsland]

King,

The Pinpoint calibration fluids are ph 7.00 and 10.00 + or - .002 at 77 degrees (clearly stated on the front of the packages). The temperature compensation tables are on the back of the packages. If the temperature of the calibration fluids are say....66 degrees, the reading your monitor should be set to is 7.016 and 10.051. If you simply calibrate the monitor to 7.00 and 10.00 disregarding the temperature of the calibration liquids, you cannot get corresponding measurements with other testing methods. The only explanation, is that the monitor is incorrectly calibrated.

[bertoni]

That's not true for a temperature-compensating pH meter. My Oakton, for example, is temperature-compensating and the temperature of the calibration liquids is handled by the meter itself, with its internal thermometer. The PinPoint unit appears to be temperature-compensating, although that's not explicitly stated.

The probe might be dirty or damaged, or the 0.2 error might simply be the accuracy limits of the two test methods.

[Boomer]

Jon

The temp of the cal solution is not the issue for the meter but the error of the cal solution itself. Yes, the meter will compensate for what ever the solution temp is but the cal solution itself can't, obviously. The meter will be be a tab off if the cal solution is not at its stated temp on the package when calibrating. That has nothing to do with ATC. But, see below.

Kingland

You are right on the cal solution. However, you are over doing it. These meters people are using do not go to .002 pH units. And .01 pH unit offset means nothing for us. We only need to deal in .1 units. But yes it is nice to get them as accurate as possible His meter will not be that far off. We are talking about < .1 pH unit (.035) off across the temp range he is at based on the package. He is off .2 pH units. BUT maybe see below

My issue with you was this;


Rinse the probe in the cup of water and try to get as much water off as possible before placing it in the 7.0 fluid. Turn the screw until you get a measurement of 7.0. Rinse the probe and place in the 10.0 cal fluid and repeat the whole process until you can go back and forth between the 10.0 fluid and the 7.0 fluid and get repeatable readings

It sounded like you were talking about using just one screw, which made no sense as there are two, i.e, Cal and Slope. Some meters do have just on screw, really cheap ones. Maybe I just jumped the gun Also one does not need to go back and forth to many times you may never hit those cal. #'s



The only explanation, is that the monitor is incorrectly calibrated

And yes you still may be very correct here. Bad cal solution, he may have contaminated it, the probe is contaminated. Do not forget the accuracy of the meter itself. PinPoint is not telling you what it is and all other meters do. More than likely it is +/- .02 pH units, if not +/- .1 pH ( which I think it may be). They only state resolution of .01 and resolution is not accuracy. Just because a meter changes its numbes by .01 when you do something or put it in any solution does not me it is that accurate. And lets not forget those kits that also may be off a tad all could lead up to an offset of .2 pH units. And I might add he is using Aqaurium Systems test kit which is corrected fo the salt error in seawater and the meter is not.

Read Randy's article I posted above up 4 posts

[bertoni]

Okay, now I get it. So the temperature charts on the pH solutions are for the buffer error, not standard pH compensation.

[lpkirby]

Boomer, Hey it makes since now... Thanks

And Thanks everyone else too.

[DrBDC]

The original calibration solutions you mentioned were the bottle type from your LFS? Here is a great article regarding the amount of error on many calibration solutions and how far off they can make your readings:

http://reefkeeping.com/issues/2005-02/rhf/index.php

[Boomer]

If was you Kirby I would get new solutions from PinPoint.

[kingsland]

Boomer,

There is no doubt that I have a tendency to overdo everything I must have one of the cheap ones (although it seemed overpriced to me) as it has only one screw and no LED. The thing I found most annoying with the monitor, was the fact that I could not get consistent readings with other test methods until compensating for temperature. It also took multiple adjustments to get it to stabilize on the correct settings. Whether its right or wrong - who knows. Thanks for the links to the articles.

[Boomer]

King then if you have only one screw the I was correct

With 1 screw, you are sure now then put in the pH 7 solution. Turn screw till it reads say 7.00, if that is the cal solution you are using. You are done. This is called absolute calibration or 1 point calibration. Don't be going back and forth with one screw

I thought you had a PinPoint

What meter do you have exactly

[lpkirby]

Yeah Boomer I have the PinPoint with a cal and a slope. I will order the calbration fluid from pinpoint.

Thanks

[XsploveReefin]

I am going through the same thing just got a pinpoint PH COntroller