Thermometer No. 1. Standard, 2-inch dial, glass-faced roasting thermometer with bimetallic sensing element sold in grocery and convenience stores. To use this correctly, the center of the bimetallic coil between the arrows must be centered in the middle of the food. This means, the tip must be inserted 1 1/4 inches past the center / coldest spot in the food.
Thermometer No. 2. Standard, 1-inch dial, bimetallic coil thermometer. Its sensing coil is constructed like that of the 2-inch roasting thermometer. To measure temperature, the tip needs to be inserted 1 1/4 inches past the center of the food so that the coil spans the center / coldest spot in the food.
Thermometer No. 3. Thermistor thermometer. The sensing unit is a 1/16-inch bead shown in the cone tip of the unit. It is held in place by epoxy. Two wires connect the bead to the electronics in the head of the unit. The unit is powered by a small battery (at least 1-year life) in the head of the unit. To measure food temperature, the tip is inserted to the center / coldest spot in the food.