Originally Posted by astewart
For the PH/Temp meters I have seen some with a temperature range of 23 to 140 F (-5 to 60 C) sold at brewing supply sites. Are these of any use to a brewer? Won't I need something with at least ATC at or above 160F.
As has been noted you will want to take measurements at room temperature. There are several reasons for this:
1. Temperature cycling is stressful to the thin glass membrane which is the working part of your meter and will result in shortened electrode life.
2. Calibrating and measuring at the same or nearly the same temperature does not make much demand on the ATC system. This is good as while ATC does work at higher temperature its is a source of error unless the electrode is perfect. The smaller the temperature excursion the smaller this error.
3. True pH (i.e. the actual pH of the mash or wort) is dependent on temperature. The difference between a pH measured at protein rest temperature and a pH measured at sachharification temperature will largely be because of temperature difference. If the pH is measured at room temperature the real pH difference, if any can be observed even though neither measurement represents the true pH.
4. It is standard practice to take measurements at room temperature. In order to be able to compare pH values you obtain to those obtained by others you want to make your measurements the same way they do.