One common application which requires a relative humidity and temperature sensor is a HVAC system thermostat control. It is based on environmental sensors and a microcontroller. The microcontroller acquires data from humidity and temperature sensors and controls the heating and cooling system. The collected data are then shown on a display that can be easily controlled by the microcontroller. Based on data from the humidity and temperature sensor, the heating and cooling system then maintains the environment at the customer-defined preferred conditions.
In a battery-powered HVAC system thermostat, one of the key parameters in the selection of components is the power consumption. The HDC302x, with 550 nA of current consumption (the average consumption over 1 s for RH and Temperature measurements), in conjunction with a MSP430, represents one way an engineer can obtain low power consumption and extend battery life. A system block diagram of a battery-powered thermostat is shown in Figure 9-1.