Temperature control is a process in which change of temperature of a space (and objects collectively there within) is measured or otherwise detected, and the passage of heat energy into or out of the space is adjusted to achieve a desired average temperature.
In the coffee making industry, the temperature control is particularly important because coffee extraction is affected directly by temperature. Low extraction temperatures will lead to under extraction, whereas high brewing temperatures will lead to over extraction.
The ideal water temperature is different for various coffee brewing methods. For some methods precise water temperature is critical, hence temperature control is important. As a general rule, the higher the temperature, the lower the margin of error needs to be. Cold brew doesn’t need an exact water temperature, as long as the water is at or below room temperature.
Temperature can be controlled directly in the coffee maker, or in the kettle. Some temperature control methods are PIDs, thermocouples, thermistors. The simplest method of controlling the water temperature for coffee extraction is a thermometer, or just an approximation. With approximation, we heat the water in a stove kettle, and then let it cool down for a predetermined time, until we approximate it will reach the desired temperature.