Cleanroom research and manufacturing processes frequently need very accurate humidity control. This is often termed “close humidity control” and can be as consistent as ±1%RH. This means the humidity provided must not deviate more than 1% above or 1% below a set point.
To achieve this the humidifier or dehumidifier must be able to respond very rapidly to a control signal coming from a humidistat, and ought to be able to fully modulate its output. A unit that is only capable of on/off operation will not be able to provide such close control than a unit with multiple stages of operation or fully modulating 0-100% operation.
Sensor accuracy is also vital. If a humidity control system is capable of very close control, at ±2%RH, but the humidistat is only providing ±5%RH accuracy, the humidity level will not be aligned to the application’s requirement.
Consistent temperature management is also essential for close humidity control. Deviations in the incoming air temperature will affect the relative humidity of the supply air from the humidity control system.