An electronic device analogous to a thermostat but which responds to relative humidity. Humidity sensors, or Humidistats are used in a number of devices including dehumidifiers, humidifiers, and microwave ovens. In humidifiers and dehumidifiers the Humidity sensor is used where constant relative humidity conditions need to be maintained such as a refrigerator, greenhouse, or climate controlled warehouse. When adjusting the controls in these applications the Humidity sensor would be what is being set. In microwaves they are used in conjunction with "smart cooking" 1-button features such as those for microwave popcorn.