Refrigerator/Freezer thermometers measure temperatures from about 70 degrees down to well below zero. If your chiller does not have external temperature readout, you will need one of these items to make sure the cabinet temperature is within the desired range. The most common methods that refrigerator/freezer thermometers use to display temperature are either with a dial or rising liquid. Dial models use expanding and contracting coils of different metals that spin the needle one way or the other as the temperature changes. The original material used in liquid thermometers is mercury. However, do to the health risks inherent with mercury poisoning; most manufacturers now use a liquid alloy of various other metals. Regardless of what is in the tube, the liquid expands or contracts as the temperature changes causing the liquid to rise or fall in the tube and indicate the temperature.