Calibration - Campbell KH20 Product Manual

KH20 Krypton Hygrometer
1985 and Buck, 1976). The rate of scaling is a function of the atmospheric
humidity. In a high humidity environment, scaling can occur within a few
hours. That scaling attenuates the signal and can cause shifts in the calibration
curve. However, the scaling over a typical flux averaging period is small. Thus,
water vapor fluctuation measurements can still be made with the hygrometer.
To see if the source tube window has been scaled, get a clean, dry cotton swab
and slide it across the source tube window. The scale is not visible to the naked
eye, but if the window is scaled, you will feel a slight but noticeable resistance
while you slide the swab across the window. There will be little resistance if
the window is not scaled. If you determine the window is scaled, you can clean
it with a wet cotton swab.
Use distilled water and a clean cotton swab to clean the scaled window. After
cleaning the window, slide a clean, dry swab across the window to confirm the
scale has been removed.
NOTE You can use the water vapor absorption coefficient for scaled
window from the calibration sheet if the window will be allowed
to scale during measurements.
7.5

Calibration

For quality assurance of the measured data, Campbell Scientific recommends
the KH20 be recalibrated every two years. Calibrations require a returned
material authorization (RMA) and completion of the "Declaration of
Hazardous Material and Decontamination" form. Refer to the Assistance page
at the end of this manual for more information.
For more information on the calibration process, refer to Appendix A,
Calibrating KH20 .
(p. A-1)
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