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pH probe calibration, question

Hi
I'm not that familiar with your Ph Controller.
But I'm sure that if you haven't re-calibrated your probe properly you will get discrepancies..with the readings.
If you take a probe out of the aquarium the Ph will rise on the monitor i think.

You should be calibrating the probe without returning it to the aquarium till the process has been completed.

The other scenario is that you cleaned the tip of the probe and it is recording a true reading.
Remember .02 swing should not cause major problems or cause algae.
hoggie
 
Thanks it was 0.2pH swing bit more than .02 :p

okay calibrated last night, tested in 7.01 + 4.01 solution, ph showed 7.01 and 4.01 so that was ok.
Now this morning I tested in only 7.01 water, it showed 7.06-7.07pH

I belive its gona bad?
 
hogan53 said:
Hi Rasmusm
Purchase new calibration fluid and get some distilled water...from the garage its cheaper.
hoggie

I dont belive its the water thats gone bad.
Cause if the calibration water isnt exactly 7.01 lets say its 7.05 infact, the probe should read 7.01 in it no matter what..
On the profillux controller you type in the 2 pH fluids you calibrate with, like calibration fluid 1 = 4.01 calibration fluid 2 = 7.01 then it says put your electrode in 4.01 10mins later it will do 3 beep's and the screens says put it into 7.01 and press enter, 10mins later beep and save the settings.

But offcause I will buy some new fluid and test
 
Hi all,
You should have 3 separate vessels for adding the pH calibration fluids.
1 for pH4
1 for pH7
1 for distilled water to clean each calibration.
That is the way to do it, rinse the probe off with the distilled H2O between each reading taken in tank or in the buffer.
On the profillux controller you type in the 2 pH fluids you calibrate with, like calibration fluid 1 = 4.01 calibration fluid 2 = 7.01 then it says put your electrode in 4.01 10mins later it will do 3 beep's and the screens says put it into 7.01 and press enter, 10mins later beep and save the settings.
That sounds fine as a calibration technique, I'd leave the probe in for 10 minutes before taking the reading. This is the method we recommend the students for our standard "Jenway 370" pH meters:
When you want to use the meter, you need to turn it on (probe in the de-ionized water) and wait for at least 5 minutes. Ideally you want to have the tank water, buffers and de-ionized all about the same temperature, even if the meter has temperature compensation. You dip the meter in the pH4 buffer, wait for at least a minute and adjust the meter to read pH4, you may find that you can store this reading as "cal. 1", you then need to sluice the probe in the de-ionized and then put it in the pH7 buffer, you will probably find that you won't get a reading of exactly pH7, you don't need to worry about this, as long as it is reasonably close (pH6.9 - pH7.1 range), this is due to the nature of the pH scale.
If the meter reads along way out at pH7 you need to go through the pH4 buffering again. Once you have readings of pH4 and pH7, you can test your tank water, the nearer the water is to pH7 the longer the meter will take to give a stable reading.

Around pH7 you will always get some movement, the difference between pH7.01 and pH7.05 is small in H+ ions, we are back to the log10 pH scale and this may just be a temperature difference. We have about 50 pH meters in the lab from £100 dip meters up to bench meters costing several thousand£, which are regularly serviced and calibrated before every use, and very few of them will read exactly the same around pH7, or read much different at pH5 etc.

I'm not sure what option you get with your pH controller, but the Hach "IQ" pH meters use an "ISFET" chip (rather than a glass membrane electrode) and are more robust (stainless steel or graphite probe) and requires far less maintenance than traditional pH probes. They are more expensive (about £250 upwards).

cheers Darrel
 
Rasmusm said:
hogan53 said:
Hi Rasmusm
Purchase new calibration fluid and get some distilled water...from the garage its cheaper.
hoggie

I dont belive its the water thats gone bad.
Cause if the calibration water isnt exactly 7.01 lets say its 7.05 infact, the probe should read 7.01 in it no matter what. :arrow:


Hi Ramusm
Your ph7 fluid has been contaminated by the Ph4 fluid that's why you need 3 separate vessels to calibrate the probe correctly.

Clean and rinse the probe with distilled water...discard this water.

Add distilled water to a clean vessel add the probe, when the reading is stable....transfer the probe to a clean vessel with the calibration ph7 fluid, when stable remove and briefly rinse in distilled water.

Do the same with ph4 fluid.......rinse briefly with distilled water after calibration.
Transfer the probe to the aquarium, you may have to wait for the probe to take a proper reading.
Throw away all the fluids you submerged the probe in.
For quick and accurate results the fluids should be between 20-25 Celsius as Darrel stated :thumbup:
Cheers
hoggie
 
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