Hygrostats of the 907032 series use the hygroscopic properties of especially prepared plastic fibers to detect relative air humidity. Once prepared, the hair measuring element is capable of absorbing moisture. The changing length is the externally measurable effect that is transmitted to a microswitch with an extremely small changeover path via a lever system. The scale ranges over an area between 30 to 100 % RH.
Values set via the value rotary knob also act as an interference to the lever system in such a way that the microswitch is actuated when the set air humidity is reached. The changeover contact can be operated as N/C or N/O contact (humidification/dehumidification) depending on the application.
Hygrostats in duct version are available as the standard version with microswitch as well as with a double changeover contact. The switching point of the second microswitch is directly coupled to that of the first microswitch; however, it can be precisely set between 0 to 15 % rel. humidity (neutral zone) on the microswitch lever by means of a screwdriver after removing the case lid.
All indoor and duct versions are available with a covered setpoint adjuster (placed beneath the case lid). This can almost fully exclude unwanted adjustment of the switching point. In addition, the highly-developed case of the indoor version not only features a high level of elegance and robustness, it also enables simple mounting on the wall, smooth surfaces, and flush-mounted boxes.