Also found in: Dictionary, Medical, Wikipedia.


An instrument that measures and controls relative humidity. Also known as hydrostat.


A device for measuring and controlling relative humidity.

humidistat, hygrostat

A regulatory device, actuated by changes in humidity, used for the automatic control of relative humidity.
References in periodicals archive ?
Local thermostats and humidistats are assumed to schedule "unoccupied" status with appropriate relaxed temperature and humidity setpoints.
One solution is to place the humidistat in a location that's both easily accessible and provides an accurate reading of the patient's immediate environment.
The other systems also have a humidistat to control dehumidifiers or change system operation in response to the space-relative humidity level.
During the cooling season, even if the indoor air relative humidity is not mechanically controlled (there is not a humidistat that senses the indoor conditions and activates the system response), the air, which is a mixture of outdoor air and recirculated indoor air, is partly dehumidified while passing through the cooling coil of the fan coil.
Disconnect the wiring to the solenoid valve and humidistat and remove the old humidifier (Photo 1).
Its digital controls include an automatic humidistat and a built-in hygrometer.
Does your MC system only control temperature (no humidistat built into the system)?
Better models have adjustable fan speeds, a built-in humidistat and automatic shutoff.
This control method can be implemented by using a humidistat wherein a humidity sensor measures the RH in the controlled space and heating of the air is initiated by the controller when the RH goes above a pre-set value.
Automatic controls for water-level height and a solid-state humidistat ([+ or -] 2%) are factory installed.