Drop Vs Digital Ph Tester

[rsumner]

From day one in this hobby I have used the API pH tester that requires a 5ml vile of your tank water and 3 drops of their solution. You try to find the closest color that matches their chart and that's your pH. Over the weekend, I got a Hanna digital pH tester. I thought my pH has been 7.6 the whole time based upon my interpretation of the API drop-tester, but the ditital meter showed my tap was just under 7.0 and my tank was 6.5 (after being dosed with co2 all day).

I did the calibration and tests today on the tanks that I run at my office, but I'll do the same with my tanks at home (using a different API kit).

Tomorrow I plan on using the 7.0 calibration solution as a method to test the API kit.

Has anyone else experienced this drastic difference or am I simply horrible at telling the difference between blue and green?

 

[TwoHedWlf]

Have you calibrated the tester? I had a PH tester and eventually stopped using it because it was pretty inconsistent and never held its calibration.

 

[Natalya]

Watching the thread...I'm extremely curious as to the results of test calibration

 

[rsumner]

And this is the dropper and digital output side by side on one of my smaller low tech planted tanks at home. The good news is that the PH is similar at home as it is at my office (a few miles up the road).

While the colors start to become a little more apparent when you have a digital meter to tell you what it is, the digital meter is an absolute must have for me now. I’m very anal about my water testing. If someone would have told me how awesome these digital meters are, I would have bought one ages ago. I would probably have a lot more skin left on my thumb from the cracking the solution causes in the drop testers.

 

[rsumner]

One more note: the digital tester included 4 and 7 PH calibration solution, so I started by doing a 2-point calibration.

 

[Natalya]

hmmm...I would read that color test as 7.0...

 

[AvalancheDave]

pH is one of the parameters where electronic meters are vastly superior to colorimetric tests.

For most other parameters, electronic probes don't make sense unless you're doing at least several dozen tests per day.

If you're really into water testing, watch eBay for Hach DR/890s or DR/900s.

 

[rsumner]

Oh wow! Now, that's a tester that I need to get. The DR900 is definitely on my Christmas list.