ph Pens vs regent and dipstick testers

[Cosmo]

I've got 2 Hanna Ph pens, 1 about 10 years old that I replaced the electrode in yesterday, and one about a week old - I get very similar readings from both of them. But.. when I use a regent based test, or a little test strip it reads about 1/2 ph lower. I put one of those seachem ph alert disks in the tank an hour ago and it's reading way way low.

I'm tempted t believe the pens, especially since both were just calibrated.

Anyone have any contrary thougths on this?

[MD.David]

First off, great aviator picture! I have his older brother! Harlequin Great Dane.... Very nice!
And I have ph and TDS pens, I think they are far more accurate.

I've got 2 Hanna Ph pens, 1 about 10 years old that I replaced the electrode in yesterday, and one about a week old - I get very similar readings from both of them. But.. when I use a regent based test, or a little test strip it reads about 1/2 ph lower. I put one of those seachem ph alert disks in the tank an hour ago and it's reading way way low.

I'm tempted t believe the pens, especially since both were just calibrated.

Anyone have any contrary thougths on this?

[rickztahone]

First off, great aviator picture! I have his older brother! Harlequin Great Dane.... Very nice!
And I have ph and TDS pens, I think they are far more accurate.

+1, trust the pens

[Discus-n00b]

Agreed with the others, properly calibrated pens would be my go to source over the others. Especially if you have 2 pens reading nearly identical.

[DJW]

Sometimes it depends on the water you are testing. If you try to use a pH pen on straight RO water it can wander because the pens need some conductivity to function. If your TDS is above 15ppm or so it should work ok.

[yogi]

I would trust a reagent test that uses drops over all of them. The API ph test uses 3 drops in the test tube and I believe it's very accurate. I would not trust test strips.

[Discus-n00b]

I don't trust the liquids as much because the variables can change so easily. Drops not the same size each time, maybe you didn't fill it up to the line the same as last time (Lines on the vial may be off), not reading colors accurately, etc. I guess it works for a general idea but it's to general for my tastes. I guess it depends what you are really counting on it for general or specific readings.