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Yoshi

calibration of digital ph metre

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so, I got the 3 buffer solutions of PH 4.01 etc.

but my question is. WHAT WATER DO YOU USE WITH IT.

I have done a lot of searching and they all say "use your 4.01 solution"

I am getting frustrated as they do not say how to create it.

My water is around ph 7.8, and rain water is around 6.8ish, my understanding is that if i added the 4.01 solution to 7.8 tap water the "solution" wouldnt become 4.01 it would only reduced it a bit.

do i need to get deionized water or distilled water?

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They are standards to check/calibrate your meter... i.e. stick the meter in ph 4.0 solution and it should read four, if not adjust pot or similar to read four. Of course cleanliness and other calibration protocols should be followed.

What are you trying to do as your question is confusing?

Edited by plecosam
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um i think i am making this confusing :(

the "solution" is little packets of powder. like flavour sachets.

so i need to mix the powder of 4.01 with some 7ph water? which would be like distilled or deionized water?

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ok sweet thanks for the details.

it has 3 point auto calibration.

im guessing it uses the temperature gage to automatically determine what the PH should be as a solution of ph 4.01 @ 25 celsius is not the same at 20 celsius.

just was a bit confused with the information on the internet on how to MAKE a ph 4.01 solution. As I have the powder + town water (town water is 7.8ph) but now i will get the power + distilled / deionized water which should get me pretty close to the 4.01 (depending on temperature)

Edited by Yoshi
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If it is a powder, you can also use tap water to make your solutions. Buffers are designed to be able to buffer (sic!) small amounts of acids and bases in the water away to automatically arrive at the right pH. As long as you don't vastly overshoot the required volume of water or add strong acids or bases your buffer will turn out ok.

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It sounds a bit complicated with powders? Any advantage to getting a powder over a made up solution?

Just wondering as the ph 7 standard (solution) I have says to replace after 12 months from opening. Was going to not rush replacing but guess around Christmas would order some more.

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I read this in the hope I would gain some useful info.

As I recall my chemistry, a buffered solution of ph4, will read 4 at both 25C & 20C.

I don't know how to make, of if you can buy buffered solutions for various ph's.

I'd expect that calibration would best be done at ph7 which is closer to the typical ph in fish tank water.

By way of comparison I observe that in swimming pool ph testing it's difficult to distinguish with any accuracy results around the range 7.4 to 7.8.

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I read this in the hope I would gain some useful info. As I recall my chemistry' date=' a buffered solution of ph4, will read 4 at both 25C & 20C. I don't know how to make, of if you can buy buffered solutions for various ph's. I'd expect that calibration would best be done at ph7 which is closer to the typical ph in fish tank water. By way of comparison I observe that in swimming pool ph testing it's difficult to distinguish with any accuracy results around the range 7.4 to 7.8.[/quote']

I've been told a few times that just calibrating at 7 is ok. I imagine there would be some instrument drift towards upper and lower ph levels without calibration for these zones but uncertain how much.

Next order of ph calibration solution I might get a ph4 solution and just see what the error is.

I can't remember how much I paid for the calibration solution but remember thinking it was like the expense of another test kit. Almost worth it not to look at colour charts though.

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I buy the calibration fluid by the bottle instead of a powder both 4 & 7. I pour some in a new plastic shot glass and place my ph pen in that to calibrate, I then throw the used solution leaving heaps left for next time. I only calibrate if in doubt or 6 monthly. As for why there is a 4 and a 7, I have not seen the need, If I calibrate with 4 the 7 is spot on? Or maybe it was still good from last time who knows!

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