Campbell Scientific KH20 Krypton Hygrometer - Manual (Page 11)

KH20 Krypton Hygrometer
5.2 Example 1, CR3000 Program to Measure Water Vapor
Fluctuations
The following example program measures the KH20 at 10Hz, and stores the
average values into a data table called ‘stats’, as well as the raw data into a data
table called ‘ts_data’.
The KH20 cannot be used for measuring absolute water vapor
concentration. NOTE
'CR3000 Series Datalogger
'This datalogger program measures KH20 Krypton Hygrometer.
'The station operator must enter the constant and the calibration value for the KH20.
'Search for the text string "unique" to find the locations of these constants
'and enter the appropriate values found from the calibration sheet of the KH20.
'*** Unit Definitions ***
'Units Units
'ln_mV ln(mV) (natural log of the KH20 millivolts)
'mV
millivolts
‘rho_w g/m^3
'*** Wiring ***
'ANALOG INPUT
'1H KH20 signal+ (white)
'1L KH20 signal- (black)
'gnd KH20 shield (clear)
'EXTERNAL POWER SUPPLY
'POS KH20 power+ (red)
' datalogger POWER IN 12 (red)
'NEG KH20 power- (black)
' KH20 power shield (clear)
' datalogger POWER IN G (black)
PipeLineMode
'*** Constants ***
'Measurement Rate
'10 Hz
Const SCAN_INTERVAL = 100 '100 mSec
'Output period
Const OUTPUT_INTERVAL = 30 'Online flux data output interval in minutes.
Const x = 1
'Unique path length of the KH20 [cm].
Const kw = -0.150 'Unique water vapor absorption coefficient [m^3 / (g cm)].
Const xkw = x*kw 'Path length times water vapor absorption coefficient [m^3 / g].
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