After calibrating the unit in both the 4.01 and 7.0 solutions in my house, I go out to test my 52 degree wine tank. Is that okay?
The SC-300 does not have temperature compensation (ATC), however the difference in a pH measurement between 52F and 70F for most solutions is pretty small, less than 0.05 pH units in most cases depending on what the solution is.
If you need to make measurements at 52F, for best accuracy we recommend calibrating with 4 and 7 solutions that are at that temperature. You can do this by storing your pH calibration solutions in the same room as your wine tanks.
You can check calibration at room temperature with a saturated solution of cream of tartar (potassium hydrogen tartrate, KHT for short). Add 1/8 tsp KHT to 20 mL distilled water, stir for 30 sec. pH is 3.55 at 70F. At lower temperatures the saturated KHT is not standardized, but will be between 3.50 and 3.60, so you can confidently check your calibration at 4 and 7 this way.
The ability to test pH with ATC may be an available feature in 2021. Keep an eye our for any announcements in our newsletters.
Additional Information:
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).
PH Variation with Temperature |
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| 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 | |