How much does pH measured with the SC-200 & SC-300 vary with temperature?

There is very little variance of the pH measurement of wine if you are operating within plus or minus 27 degrees F (+/- 15°C) of room temperature,  77° F. The table below will let you know what are typical readings from the pH meter using our reference solutions or other buffers at different temperatures. If you operate the pH meter close to room temperature,  77° F (approximately 25°C) , with the wine sample and the reference solutions also close to room temperature, you should have acceptably accurate measurements with a variance +/- 0.02 pH units.
 
If you are operating in outdoor conditions or in a cold cellar, the chart below should let you know how much variance is to be expected regarding pH buffers and our pH 4 and 7 reference solutions as well. Since most wines fall within a pH range 3.0 to 4.0, you can roughly approximate the variance in pH to be similar to a pH 3 buffer, a pH 3.49 check solution  (50 mM sodium diglycolate), and the pH 4.01 reference solution provided with the SC-200 and SC-300. Even a change in temperature of +/- 27°F from room temperature doesn’t change the pH more than +/- 0.03 pH units with the three solutions mentioned above, so unless you are operating below 50°F or above 104°F, the pH measurements accuracy due to temperature variation is very close to the error of the instrument (+/- 0.02 pH). For more information about temperature effects on pH calibration, see here.

 

PH Variation with Temperature

     
       
  Temperature °C Temperature °F pH
pH 3 buffer (phthalate) 0 32 2.91
  5 41 2.912
  10 50 2.918
  15 59 2.919
  20 68 2.924
  25 77 2.932
  30 86 2.936
  35 95 2.944
  40 104 2.953
  45 113 2.962
  50 122 2.973
  55 131 2.984
  60 140 2.998
pH 3.49 check solution 5 41 3.47
10 50 3.47
15 59 3.48
20 68 3.48
25 77 3.49
30 86 3.50
35 95 3.51
40 104 3.53
50 122 3.56
pH 4.01 reference solution 0 32 4.000
  5 41 3.998
  10 50 3.997
  15 59 3.998
  20 68 4.000
  25 77 4.005
  30 86 4.011
  35 95 4.018
  40 104 4.027
  45 113 4.038
  50 122 4.050
  55 131 4.084
  60 140 4.101
pH 7.00 reference solution  0 32 7.115
  5 41 7.083
  10 50 7.056
  15 59 7.032
  20 68 7.012
  25 77 6.994
  30 86 6.983
  35 95 6.975
  40 104 6.968
  45 113 6.97
  50 122 6.97
  55 131 6.97
  60 140 6.974

 

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