Campbell KH20 Product Manual page 15

8
7.5
7
6.5
6
5.5
5
4.5
4
1.74 3.02 4.17 5.44 6.71 7.95 9.2
Vapor Density (g/m
FIGURE A-1. KH20 ln(mV) vs. Vapor Density
We can perform the linear regression on the plot to obtain the slope for the
relationship between the ln(mV) and the vapor density. The slope for the graph
is the coefficient, k x. TABLE
w
analysis. The slope is the product of the absorption coefficient of water vapor,
k , and the KH20 path length, x.
w
TABLE A-1. Linear Regression Results for KH20 ln(mV)
Y Intercept (ln(V
If we substitute these values, along with the measured lnV into equation A-3,
we can obtain the water vapor density, ρ
calibration twice for each KH20: once with the window cleaned, and again
with the window scaled. We then break up the vapor density range into dry and
wet ranges, and compute the k
range. If you know the vapor density range for your site, it is recommended
that you select the coefficient, k
or the wet range. If the vapor range for the site is unknown, or if the vapor
range is on the border line between the dry and the wet ranges, use the value
for the full range. TABLE
calibration certificate contains. The data shown in TABLE
actual KH20.
Appendix A. Calibrating KH20
10.47 11.69 12.9 14.22 15.46 16.78 18.04 19.25
3 )
A-1 shows the result of linear regression
vs. Vapor Density
Description
Slope (xk )
w
)
0
. Campbell Scientific performs the
w
values for each sub range, as well as for the full
w
, that is appropriate for your site, the dry range
w
A-2 shows the final calibration values the KH20
Values
–0.205
8.033
A-2 is from an
A-2