This is a short post to clarify something I had in my mind about single point calibration of pH sensors.
I have a (Hanna Instruments) GroLine (HI9814) pH/EC and a Halo (FC2022) pH sensor. I almost always use the GroLine sensor because it can simultaneously measure EC and I have its Quick Cal solutions to do single point combined calibration of pH and EC which is very convenient. Because the solutions I do measurements almost always have pH between 5-7, I was thinking single point calibration should work fine, but I did not know how accurate it would be as it reaches to pH 4 or 10.
So today I take out my Halo (FC2022) pH sensor and would like to clarify this. I did a three point (4.01, 7.01, 10.01) calibration of the Halo sensor and then measured the pH of these buffer solutions both with Halo and with GroLine sensor. To my surprise (maybe it is not surprising I dont know), GroLine sensor was within 0.1 of the pH value measured by the Halo sensor. So for my use, GroLine sensor is highly accurate even going to 4 and 10, using only a single point calibration.
Note: I only did single-point calibrations since I purchased the GroLine sensor, I have not done any two point calibration.
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