Portable Ph Metre?

[kennygater]

hi i have got myself a portable ph metre with temperature display because the test kits i was using didnt give a good enough reading. has anyone got one of these? the instructions are rubbish, it dosent explain what the buffer sollutions are and when i put the pen in the tank it doesnt stay at a number. can anyone help?

 

[bobf]

hi i have got myself a portable ph metre with temperature display because the test kits i was using didnt give a good enough reading. has anyone got one of these? the instructions are rubbish, it dosent explain what the buffer sollutions are and when i put the pen in the tank it doesnt stay at a number. can anyone help?

Hi Ken - don't know if you ever got this sorted, but I got one of these recently too.

I think we have the same kit as mine does temp and Ph and comes with a couple of bottles, though mine were of calibration fluid, not buffer.

To calibrate (assuming you have the calibration fluid - or else a liquid of a known Ph - sure the chemists on here can help on that!) what I did was pour the fuid in an egg cup as the neck of the bottle is too narrow, and hold the device in it to see the reading - the numbers do wander up and down a bit at first but settle within a '00th of a 'Ph' within a few seconds. the trick then is to adjust the thing to show the same (more or less) Ph as the known value. Mine has a tiny screw near the pocket clip on the reverse and comes with a tiny screwdriver too. The soloutions with mine are Ph 6.964 and 4.003 - the instructions say try both, but don't say which to believe - to the extent there was any difference I favoured the higher test soloution as the more important one. The readings are given to two decimal figures on the 'pen' and the test soloutions are quoted to three. That being said the pen is only quoted as being accurate to plus or minus one decimal figure anyway, so no point losing too much sleep over it!

I do use mine and I'm happy it serves a purpose - in practice I always wait 20-30 seconds for the reading to settle and then it only fluctuates by a couple of hundredths either way once it has settled down.

One final point - my instructions do say "...wash the electrode in distilled water and suck it with filter paper" - I'm still trying to figure that one out!

 

[kennygater]

thanks mate, that helps alot. i had give up on it.

 

[The-Wolf]

we have one of these at work (supplied by TMC)
bobf seems to have covered everything, I just wanted to add...
rather than buy more calibration fluid (when needed)
use pasturised milk at room temperature (IE 20c) as that has a pH of 6.7

 

[Underwurlde]

One final point - my instructions do say "...wash the electrode in distilled water and suck it with filter paper" - I'm still trying to figure that one out!

This is what happens when translating a descriptive language like Chinese into a phonetic one like English.

It means, wash the electrode in distilled water and dry it using kitchen towel. The "suck it with filter paper'" is referring to the absorbtion of the paper towel.



Andy

 

[bobf]

One final point - my instructions do say "...wash the electrode in distilled water and suck it with filter paper" - I'm still trying to figure that one out!

This is what happens when translating a descriptive language like Chinese into a phonetic one like English.

It means, wash the electrode in distilled water and dry it using kitchen towel. The "suck it with filter paper'" is referring to the absorbtion of the paper towel.



Andy

Thanks Andy, but "I'm still trying to figure that one out" was my attempt at humor!

Maybe that needs translating too?







I'll get my coat...

 

[BigIan]

i have the same "suck it and see" instructions, but unfortunateky mine didn`t come with any calibration fluid, but i will be off to get my self a bottle of pasturised milk tomorrow... yeay

 

[SkiFletch]

Just have to chime in here. Although I have no experience with AQUARIUM digital pH meters, I have significant experience in using similar products commercially available for science and industry. It has been my experience that all membrane or solenoid type digital pH meters are exceptionally accurate right after calibration. It has also been my experience that these meters have a tendency to drift away from cal easily, often, and do so in dramatic fashion. I personally would never use one in my system. While titration chemical reactions and other chemical means of measuring pH are more dime consuming and potentially less accurate, if done properly they are much more reliable IMO

 

[Underwurlde]

@bobf, now I'm laughin'

 

[bobf]

Just have to chime in here. Although I have no experience with AQUARIUM digital pH meters, I have significant experience in using similar products commercially available for science and industry. It has been my experience that all membrane or solenoid type digital pH meters are exceptionally accurate right after calibration. It has also been my experience that these meters have a tendency to drift away from cal easily, often, and do so in dramatic fashion. I personally would never use one in my system. While titration chemical reactions and other chemical means of measuring pH are more dime consuming and potentially less accurate, if done properly they are much more reliable IMO

I'm beginning to share your view Ski - mine does seem to need calibrating every time I use it, which means the exercise ends up taking longer that the 'colour chart' route does. Typically, mine seems to drift downwards by around 0.3 - 0.4. Looks like you gets what you pay for!

Thats another $17 donated to the HK economy for no good reason - still, the kids are made up with the stamps off the envelope!

 

[Donya]

Not all pH meters work calibrated to fluids with intermediate pH values...you can try it but make sure you have something to check it against before you use it to adjust your tank water. I tried similar tricks with my digital meter, which requires two values to calibrate, and my pH readings were way off in the higher range as a result. I mean way off as in sometimes showing me values over 10 and 11 when the fluid being tested was actually in the 8.0-8.5 range. I could only get accurate readings when I used fluids that were very close to the two endpoint readings for my meter (7 and 10).

 

[Underwurlde]

Yep, for a linear equation y = mx + c where m = (y1-y2) / (x1-x2).
The further apart the points x1y1 and x2y2 the more accuratly the linear equation will represent reality.


.....I'll get my coat.