The Beverage Air 402-223B Thermometer-Vertical is an instrument that determines the internal temperature through a sensing element that reacts to the variation of heat and transfers that data to the scale on the stem. The internal components respond to the change in temperature and move the indicator up and down the vertical scale to indicate the current conditions, and it is in an up... https://partsfe.com/thermometer-vertical-for-beverage-air-part-402-223b