PH monitor suggestions - continual use

Andrew Butler

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I agree with the reservations of others about continuous pH monitors. That's why I would be very hesitant about using one of these to control CO2 injection
I've made no mention that this has ever been my intention; merely to have a rough idea how the CO2 levels change over a 24 hour period and longer.
Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH?
I appreciate there's always margin for error and results also rely on 'ideal' conditions; Hanna do make a 'Millesimal Buffer Solution' which is accurate to ±0.002
so could possibly support the ±0.005 of the HI-11102 HALO device although I'm just guessing here.

I think if I need a device this would be more than accurate for my needs and is only to keep an eye on the CO2 levels and monitor them out of interest as much as anything else.
Thanks for your input though
 

dw1305

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Hi all,
Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH? Not that there's anything wrong with calibrating to two decimal places.
There is of course margin for error but this is just to try and answer your question here.
I've been thinking about this, and I may be wrong, but isn't there a more fundamental issue, which is that the decimal places on pH values can differ by several orders of magnitude, because pH is a -log^10 scale representation of the hydrogen ion activity?

I think that implies that the 3rd decimal place at pH4, is the same as the unit at pH7? You've gone through three orders of magnitude, from 10^-4 to 10^-7.

When-ever I think that I understand pH something else comes up that makes me think I don't at all.

This is a "weak acid / weak base" <"titration curve">. I think that is where we are when we add CO2, to 4dKH solution, and the bit we are interested in is somewhere around the equivalence point.

wawb.gif

cheers Darrel
 
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papa_c

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22 Jan 2013
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Must admit I'm enjoying reading the debate...however are we really concerned about measureong ph to the 1/1000th when we does EI based on teaspoon measurements!

Sledgehammer and walnut springs to mind
 

jaypeecee

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Bracknell
I've made no mention that this has ever been my intention; merely to have a rough idea how the CO2 levels change over a 24 hour period and longer.
Hi @Andrew Butler

Apologies. I am fully aware that you had no plans to use the pH monitor to actually control CO2 injection. I obviously implied otherwise. Have you had a chance to look at some of my suggestions?

JPC
 

Andrew Butler

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1 Feb 2016
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Location
Banbury, Oxfordshire
have no need for actually measuring pH to an accuracy of +/-0.001
Completely agree with you here, I guess just the more accurate a device is the less margin for error.
Have you had a chance to look at some of my suggestions?
I've had a very quick look but need to sit down next year and have a proper look through them, thanks though.
I do see the Hanna bluetooth version as something that could work for me; I just need to look into things a bit more as money soon starts getting out of hand and I could just use my handheld.
Very interested to look into options as I'm in no rush.
 
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