You probably know that temperature control is a key way for brewers to ensure consistent, quality beer from one batch to the next. Professionals enjoy the benefit of glycol-cooled, jacketed cylindroconical fermentation tanks, but we homebrewers typically improvise a temperature-regulated fermentation chamber or even an ice bath. Just measure the temperature of the beer and let a controller turn on the cold as needed.
Alas, as with human beings, there are multiple places at which one may take a beer’s temperature. Ideally you’d just sanitize the probe and drop it directly into the fermenting beer. In practice, however, this is probably a bad idea unless said probe is specifically rated for submersion in liquid. Here, then, are the two of the most common ways to measure temperature without voiding your controller’s warranty.
Within the Beer Itself via a Thermowell
This is the best place to measure because the beer in the middle of the fermentor can be much warmer than that near the wall, perhaps by as much as 10°F (5.6°C). Measuring your evolving beer at its warmest spot ensures that things stay nice and cool during the most active phase of fermentation.
