Hygrostat AFS-G1

The Hygrostat AFS-G1 serves as a two-position controller to regulate relative humidity indoors or in air ducts. The moisture sensing element in the sensor comprises several strips of plastic fabric each with 90 fibres of 3 μm diameter. These plastic fibres undergo a special process to acquire hygroscopic properties, this means that they absorb and release moisture. The molecular structure of the fibres changes when they absorb water, giving rise to a measurable change in length.

The length of the plastic fibres is thus a measure of the relative humidity. The swelling effect, acting primarily in longitudinal direction, is transferred over a suitable lever system to a microswitch with an extremely small changeover movement. The measuring element reacts quickly and accurately to the change in humidity. The setpoint is set with the setpoint button so that the microswitch is actuated by the lever system when the humidity setpoint is reached.

The special treatment of the measuring element ensures that its hygroscopic properties remain stable, that is sensitivity is maintained until destroyed by external influence. Regeneration found in conventional instruments is not required, but is also not damaging. The harp-shaped measuring element is protected by a perforated probe tube and is open to the housing. The hygrostats are designed for unpressurized systems.