Looking for a ph water meter that doesnt need calibration

[JustAnotherFarang]

Hi guys

 

I want to buy a ph tester and can only find the cheap ones on Lazada which need constant calibration every month.  Ideally I want to buy something more expensive that rarely if ever needs calibration.  I did try a swimming pool tester but it seemed wildly inaccurate.  Can anyone point me in the right direction please

 

Cheers

JAF

[Time to grow]

I have an aquaponics system stocked with Tilapia. The pH is critical and I monitor it regularly. I tried a couple different models of the electronic handheld variety but the readings were suspicious on both of them. I ended up resorting back to the liquid drops which are quick and easy to administer. I don't have evidence to condemn the electronic versions but I have much more faith in the liquid drop method for determining pH. 

[BritManToo]

5 hours ago, JustAnotherFarang said:

want to buy a ph tester and can only find the cheap ones on Lazada which need constant calibration every month.  Ideally I want to buy something more expensive that rarely if ever needs calibration.

The cheap ones work well, no need for calibration PH of milk is 6.6.

Dip it in a glass of milk, note the difference between the reading it gives and 6.6 and you're good to go.

 

I've got one and it works a treat.

[JustAnotherFarang]

12 hours ago, BritManToo said:

The cheap ones work well, no need for calibration PH of milk is 6.6.

Dip it in a glass of milk, note the difference between the reading it gives and 6.6 and you're good to go.

 

I've got one and it works a treat.

Now that is incredibly useful information and something worth remembering in the short term as its the calibration that irks me.  I will give it a go in the short term

 

cheers

JAF

[carlyai]

Here's a test kit I have for aquaponic systems. Haven't used it yet as my aquaponics installation is, as usual, like the pipe work on beach road Pattaya; way behind schedule.

[cleopatra2]

52 minutes ago, JustAnotherFarang said:

Now that is incredibly useful information and something worth remembering in the short term as its the calibration that irks me.  I will give it a go in the short term

 

cheers

JAF

The use of one known ph substance would require any calibration drift to be linear. This is not usually the case . It is more common to be a curve and this is the reason that a minimum of 2 solutions are used .

 

If you do not wish to calibrate then either use litmus paper or the drop solution .

[JustAnotherFarang]

I have already bought the drops as recommended but I am slightly colour blind with shades of green and cant quite make my mind up unless someone else is there.  Its a fairly reliable system so maybe someone can point me in the right direction to say buy 100ml instead of the smaller 10 ml bottles.  Also bought some litmus paper which seems a relaible method I can use as well

 

JAF

Edited March 3, 2020 by JustAnotherFarang
more info

[Monomial]

There is no such thing as a pH meter that does not require calibration. Expensive pH meters, such as used in scientific labs, require calibration at 5 or more points, vs. the cheap ones that only require calibration at 2.

 

The reason is because the resistance of the electrode changes over time. As it ages and oxidizes, the subtle changes have a tiny effect on the resistance, and this can dramatically affect the current and voltage readings, which can require microvolt resolution to determine pH. The more accuracy you want, the more often you need to calibrate and the more points you need. High accuracy requires calibrating the non linearity of the electrodes. The more expensive the device, the more accuracy it will provide, and the more often you will need to calibrate.

 

So you are effectively asking for something that is impossible when saying you don't want to calibrate. If you really don't want to calibrate, just guess. That doesn't require any calibration at all.  Or, you can skip the calibration, and simply accept the decline in accuracy over time.

 

There are cheap, disposable pH pen meters that come from the factory precalibrated, but they aren't designed to provide accurate readings for more than a month. The electrode will quickly become worn, and then you throw them away.