They are available in a large variety of types: beads, disks, washers, rods, etc. Ther- mistors have a negative temperature coefficient. Their resistance decreases when the sensed air tem- perature increases. The resistance of a thermistor may drop from approximately 3800 to 3250 when the sensed air temperature increases from 68 to 77°F (20 to 25°C). Recently developed high-quality thermistors are accurate