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Hygro and Hygrothermal Transducer (Hygrometric) (907031)


For measuring relative air humidity and temperature

  • For indoor, air duct, and outdoor mounting
  • With resistance, current, or voltage outputs
  • Can be used continuously in areas of high humidity (up to 100 % RH) (duct version)
  • No voltage feed required for passive devices
  • In normal circulated air, the sensing element is largely maintenance free


For a wide range of applications in the following areas:

  • Climate measurement technology
  • Air technology
  • Humidification and dehumidification technology
  • Fruit and vegetables (storage)
  • Ripening chambers
  • Greenhouses


Humidity measuring probes of the 907031 series use the hygroscopic feature of especially prepared plastic fibers to define the relative air humidity. Once prepared, the installed humidity sensing element is capable of absorbing moisture. Length variation is the external measurable effect. Humidity-dependent length variation is detected with precision mechanics, transferred to a potentiometer, and output as a linear resistance output at the connection terminals.
The standard output is 100 to 138.5 Ω and corresponds to a Pt100 signal. This allows direct connection to standard devices from the measuring, control, and recording range for further processing of the measuring signal.
Further device versions with different resistance outputs, with standardized current and voltage output signals, and humidity measuring probes complemented by temperature recording round off the delivery range.

The humidity measuring probes are suitable for air conditioning applications as well as for humidity measurements in industrial fields. The high resistance of the sensing element to water is an advantageous feature allowing permanent use of the device in high humidity applications through to saturation. Moreover, in normal circulated air the sensing element is almost maintenance free. Dirt caused by dust-laden air can be cleaned by washing.
The working range of the sensing element is 30 to 100 % RH in permissible ambient temperatures from -40 to +80 °C. Device versions with a passive output offer a further advantage by not requiring a dedicated voltage supply for operation.