This product is no longer available and has been replaced by: CPEC310,CPEC300-Series,CPEC306,EC150,IRGASON.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

Detailed Description

The KH20 is typically used with a CSAT3 Sonic Anemometer in eddy-covariance systems. This highly sensitive hygrometer measures rapid fluctuations in atmospheric water vapour. It does not measure absolute concentrations. The KH20 is compatible with most of our dataloggers.

Routine maintenance is required to keep source windows free of scale. The KH20 can be used with the window scaled if scaled calibration is used.


Calibrated 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
21X (retired)
CR10 (retired) The CR10 requires a VDIV2:1 voltage divider.
CR1000 (retired)
CR10X (retired) The CR10X requires a VDIV2:1 voltage divider.
CR200X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR500 (retired)
CR5000 (retired)
CR9000 (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.


Frequently Asked Questions

Number of FAQs related to KH20: 4

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  1. 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 returned material authorization (RMA) number. 

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

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

  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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