Home Brewing Digital Temperature Controller
It seems like often times home brewers place a ton of attention of the brewing process and not enough on the fermentation process. The truth is that both are critical to making a good beer. Brewing yeast is highly temperamental and is heavily impacted by temperature. If the temperature is too cold it begins to shut down, slowing replication and fermentation. If this happen at the wrong time in the fermentation process you will wind up with a sweet and under fermented beer and potentially bottle bombs. If your temp gets too high high you may flash ferment your beer ending up with a bunch of off flavors created by your yeast. What you want in a nice consistent temperature, specific to your lager or all yeast strain. A temperature that is consistent 24 hours a day, not fluctuating wildly day and night. For most ale yeast strains you are looking for a target temp of about 68 F. Depending on where you live, what time of the year it is and what type of equipment you have available will determine how you want to handle controlling your fermentation temperate. In any case, you are probably going to want to purchase a temperature controller such as the Ranco Digital Temperature Controller pictured above. I have used both Ranco and Johnson controllers and would recommend either; the Ranco just tends to be a little less expensive. In an ideal situation you would hook the temperature controller to a chest freezer or refrigerator to help insulate the beer from the elements.
If you are looking for a digital temperature controller for your home brewing fermentation, MoreBeer currently has the Ranco on sale for $83.95 and is Available Here