This product is no longer available and has been replaced by: EC150,CPEC306,CPEC300-Series,CPEC310,IRGASON. Some accessories, replacement parts, or services may still be available.
KH20 Krypton Hygrometer with Case
Services Available
Repair Yes
Calibration Yes
Free Support Yes


The KH20 is a highly sensitive hygrometer designed for measurement of rapid fluctuations in atmospheric water vapor, not absolute concentrations. It is typically used together with a CSAT3B in eddy-covariance systems. 

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Benefits and Features

  • Compatible with most Campbell Scientific data loggers
  • High frequency response suitable for eddy-covariance applications
  • Well-suited for long-term, unattended applications


KH20 with mounting equipment (sold separately)
KH20 with mounting equipment (sold separately)
KH20 with mounting equipment (sold separately)
KH20 mounted with the CSAT3B and FW3 (items sold separately)
KH20 mounted with the CSAT3B, FW3, temperature and relative humidity probe, and tripod (items sold separately)

Technical Description

The KH20 is typically used with a CSAT3B Sonic Anemometer in eddy-covariance systems for measuring water vapor flux. This highly sensitive hygrometer measures rapid fluctuations in atmospheric water vapor. It does not measure absolute concentrations. The KH20 is compatible with most of our data loggers.

Routine maintenance is required to keep source windows free of scale. You can use the water vapor absorption coefficient for scaled window from the data report if the window will be allowed to scale during measurements.


Range 1.7 to 19.5 g/m3 (nominal)
Type Ultraviolet krypton hygrometer
Input Voltage Range 10 V to 16 Vdc
Current Consumption 20 mA max (at 12 Vdc)
Power Consumption 0.24 W
Output Signal Range 0 to 5 Vdc
Cable Length 7.62 m (25 ft)
Mounting Pipe Length 50 cm (20 in.)
  • 29 x 23 x 3 cm (11.5 x 9 x 1.25 in.) for sensor head
  • 19 x 13 x 5 cm (7.5 x 5 x 2 in.) for electronics box
  • 29 x 18 x 6.5 cm (11.5 x 7 x 2.5 in.) for rain shield with mount
  • 64 x 38 x 18 cm (25 x 15 x 7 in.) for carrying case
Weight 6.8 kg (15 lb)


Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.


Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR216X (retired)
CR5000 (retired)
CR800 (retired)
CR850 (retired)
CR9000X (retired)

Additional Compatibility Information

Data Logger Considerations

The KH20 requires one single-ended analog input (signal is 0 to 5 Vdc), 12 V power, and ground.

Resources and Links

FAQs for

Number of FAQs related to KH20: 4

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  1. The sensors used in the eddy-covariance flux application, including the KH20, are not supported by SCWin.

  2. For a description, refer to the “Basic Measurement Theory” section in Appendix A of the KH20 Krypton Hygrometer Instruction Manual.

  3. The seal around the source/detector tubes is not user serviceable. If the seal has failed, return the KH20 to the factory for repair. Follow the steps listed on our Repair and Calibration page to request a return material authorization (RMA) number. 

  4. An open-path eddy-covariance program is available for purchase as pn 18442CRBasic Basic Eddy Covariance Program. This is the program without energy balance sensors. Also available is pn 18443, CRBasic Extended Eddy Covariance Program, with energy balance sensors. To order a custom configured program, contact the Micrometeorology Flux group for assistance.

Case Studies

California: Turbulence Study in Walnut Orchard
Understanding the exchanges of energy, water, and carbon dioxide between the atmosphere, land, and more
Korea: Flux Monitoring over a Rice Paddy
With instrumentation and help from Campbell Scientific, personnel from the Department of Atmospheric Sciences more

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