Comparison of pH probes

[JulesH]

Hi,

I have an interesting issue with my pH probes. I have two probes in the sump of my 320 litre frag tank, one made by reef factory (probably better known in Europe/UK) and the second device by Neptune running in conjunction with my Apex.

Both are calibrated, the Apex probe with the 7 and 10 solutions, whilst the reef factory probe uses 4 and 7 solutions. I was hoping that Reef factory were going to change their calibration solutions to bracket sea water values, but that has not happened yet.

Here is the conundrum, the reef factory reads higher than the Apex probe by approximately 0.46 of a pH measurement. I have recorded and graphed a 24 hour period of both probes. I dose Kalk overnight, only 0.5 litre. I am trying to figure out which probe is giving me a more accurate representation of my tank's pH? As you can see both curves follow each other quite well.

Thanks for looking

Julian

 

[Bleigh]

You could purchase some reference standards on amazon and determine which one is most accurate from that. Another option is to look at the percentage error for both probes. You can add that to your plot and determine the overlapping portion to be most reflective of the "true" ph.

 

[JulesH]

Bleigh, thanks for your reply. I am going to buy some third party reference standards when I get home, ones that will cover the 4, 7 and 10 used by both probes. I shall look into the the instrument associated errors.

Julian

 

[Dburr1014]

Bleigh, thanks for your reply. I am going to buy some third party reference standards when I get home, ones that will cover the 4, 7 and 10 used by both probes. I shall look into the the instrument associated errors.

Julian

You can also make reference standards from house hold items.
Or just use the 7 and 10 and see if they read right, right now without re-calibrating.

 

[gbroadbridge]

Hi,

I have an interesting issue with my pH probes. I have two probes in the sump of my 320 litre frag tank, one made by reef factory (probably better known in Europe/UK) and the second device by Neptune running in conjunction with my Apex.

Both are calibrated, the Apex probe with the 7 and 10 solutions, whilst the reef factory probe uses 4 and 7 solutions. I was hoping that Reef factory were going to change their calibration solutions to bracket sea water values, but that has not happened yet.

Here is the conundrum, the reef factory reads higher than the Apex probe by approximately 0.46 of a pH measurement. I have recorded and graphed a 24 hour period of both probes. I dose Kalk overnight, only 0.5 litre. I am trying to figure out which probe is giving me a more accurate representation of my tank's pH? As you can see both curves follow each other quite well.

Thanks for looking

Julian

If you dissolve 3.8 g of household Borax in a litre of water you will have pretty close to pH 9.19 reference.

 

[JulesH]

Hi all,

I am back from my travels I have recalibrated both my pH probes with 4, 7 and 10 pH standards. Attached is another 24 hour comparison dataset of my two probes. As mentioned previously they both follow the pH trend pretty well. I have not been able to ascertain the accuracies of the two instruments, thus I am not able to weight the probes accordingly.

If you look at the graph I have included a median line. I was thinking of using the median as my actual pH level for my Kalk dosing.

Is this feasible?

Thanks for looking

Julian

 

[gbroadbridge]

Hi all,

I am back from my travels I have recalibrated both my pH probes with 4, 7 and 10 pH standards. Attached is another 24 hour comparison dataset of my two probes. As mentioned previously they both follow the pH trend pretty well. I have not been able to ascertain the accuracies of the two instruments, thus I am not able to weight the probes accordingly.

If you look at the graph I have included a median line. I was thinking of using the median as my actual pH level for my Kalk dosing.

Is this feasible?

Thanks for looking

Julian

I don't see that it matters.

Pick either.