Proper pH Reading

[mainshipfred]

Rich @rsportsman I noticed you have recently made a few posts concerning the Vinmetrica. I can get different pH readings depending on how I use the probe.

This has always puzzled me and several time I contacted tech support but maybe I never explained my issue properly.

This is typical but I can give you exact details from yesterday.

I placed the probe in the sample and got a reading eventually evening out to around 3.82. The I moved then probe back and forth in the sample and it kept dropping and finally bottomed out at 3.69. I stopped moving the probe and let it sit there for a few minutes in which time it went up to 3.72/3.73 and stayed there for at least 5 minutes.

So which is the correct reading or am I doing something wrong?

 

[BarrelMonkey]

Rich @rsportsman I noticed you have recently made a few posts concerning the Vinmetrica. I can get different pH readings depending on how I use the probe.

This has always puzzled me and several time I contacted tech support but maybe I never explained my issue properly.

This is typical but I can give you exact details from yesterday.

I placed the probe in the sample and got a reading eventually evening out to around 3.82. The I moved then probe back and forth in the sample and it kept dropping and finally bottomed out at 3.69. I stopped moving the probe and let it sit there for a few minutes in which time it went up to 3.72/3.73 and stayed there for at least 5 minutes.

So which is the correct reading or am I doing something wrong?

You should move the probe back and forth, or use a stirred vessel. Otherwise, you'll get a local depletion of ions in the solution surrrounding the probe, which can lead to the signal not fully reaching equilibrium or drifting as you describe.