are instruments used for determining the dew point
. They consist of a small heating element surrounded by a solution of lithium chloride
. As the LiCl absorbs moisture from the air, conduction across the heating element increases, current in it increases, and heat increases, evaporating moisture from the salt solution. At a certain temperature the amount of moisture absorbed by the salt solution equals the amount evaporated (equilibrium).
Inside the dewcell core a thermistor composite (or other temperature measurement device) changes resistance with the temperature created by the heating. A front end processor provides a reference voltage, measures the output of the network, and calculates the dewpoint.