pH Meter Suggestions

[rwyoung]

From memory:

At 20C, the ideal glass pH electrode would have, according to Herr Nernst, a slope of 58.2mV/pH and an intercept of 0mV at pH 7.

The ideal slope drops to something like 54mV/pH at 0C and increases to something near 64mV/pH at 50C AT 40C I'd guess it is around 62mV/pH.

What it all works out to is something like -0.2 mV/C to adjust the slope.

This all assumes a perfect probe which will never be the case. Your best bet for a meter without ATC, is to calibrate at or near the temperature of interest and if you can, using the charts that come with the buffer solutions, enter the corrected pH for the buffer temperature.

If you are using an IsFET or Iridium oxide probe, the idea is the same but the slope and intercepts are different.

 

[Photo Engineer]

Without checking the Nernst values, I would say I could agree.

OTOH, if you calibrate at 20C all the time, then the error is at least constant and reduces the complexity of the calibration process. You will therefore see all Kodak solution pH values reported at 20C regardless of the temperature at which they are used.

PE

 

[DarkroomExperimente]

Thanks

can't wait to get my new toy

 

[Mick Fagan]

My personal experience with these meters is; the best model is the one which will do what you require and is waterproof, as opposed to water resistant.

I have had pH meters which require the solution to be at 20C for correct measurements, but after having a meter with inbuilt temperature compensation, for times when I couldn't get the temperature down to 20C, I'm sold on the idea.

Sort of a bit like a pH meter auto-focus I suppose.

However I really think whatever you get, ensure it's waterproof, these little meters are so easy to slip into a solution.

Mick.