Campbell KH20 User manual

KH20
Krypton Hygrometer
Revision:
05/2020
Copyright ©
2010 – 2020
Campbell Scientific, Inc.

i
Table of Contents
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1. Introduction................................................................ 1
2. Precautions................................................................ 1
3. Initial Inspection ........................................................ 1
3.1 Components .........................................................................................1
4. Overview .................................................................... 1
5. Specifications ............................................................ 2
5.1 Measurements ......................................................................................2
5.2 Electrical ..............................................................................................2
5.3 Physical ................................................................................................2
6. Installation ................................................................. 3
6.1 Siting ....................................................................................................3
6.2 Mounting..............................................................................................3
6.2.1 Parts and Tools Needed for Mounting ..........................................3
6.2.2 Mounting the KH20 Sensor ..........................................................3
6.2.3 Mounting the Electronics Box ......................................................4
6.3 Wiring ..................................................................................................6
6.4 Data Logger Programming...................................................................7
6.4.1 KH20 Calibration..........................................................................7
7. Maintenance and Calibration .................................... 7
7.1 Visual Inspection..................................................................................8
7.2 Testing the Source Tube.......................................................................8
7.3 Testing the Detector Tube....................................................................8
7.4 Managing the Scaling of KH20............................................................8
7.5 Calibration............................................................................................9
Appendices
A. Calibrating KH20.................................................... A-1
A.1Basic Measurement Theory............................................................. A-1
A.2 Calibration of KH20........................................................................ A-1
B. Example Program .................................................. B-1

Table of Contents
ii
C. EasyFlux®DL CR6KH20 ........................................ C-1
C.1 Introduction......................................................................................C-1
C.2 Precautions .......................................................................................C-2
C.3 Wiring ..............................................................................................C-2
C.3.1 Required Sensors ......................................................................C-3
C.3.2 Optional Sensors .......................................................................C-3
C.3.2.1 VOLT116 Module..........................................................C-3
C.3.2.2 Barometer .......................................................................C-4
C.3.2.3 Fine Wire Thermocouple................................................C-4
C.3.2.4 GPS Receiver .................................................................C-5
C.3.2.5 Radiation Measurements Option 1 .................................C-5
C.3.2.6 Radiation Measurements Option 2 .................................C-6
C.2.3.7 Precipitation Gage ..........................................................C-8
C.2.3.8 Soil Temperature ............................................................C-9
C.2.3.9 Soil Water Content .........................................................C-9
C.3.2.10 Soil Heat Flux Plates ....................................................C-10
C.4 Operation........................................................................................C-12
C.4.1 Set Constants in CRBasic Editor and Load Program ..............C-12
C.4.2 Enter Site-Specific Variables with Data Logger Keypad or
LoggerNet............................................................................C-14
C.4.3 Data Retrieval .........................................................................C-19
C.4.4 Output Tables..........................................................................C-19
C.4.5 Program Sequence of Measurement and Corrections .............C-36
C.5 References......................................................................................C-37
D. Equations and Algorithms of Water Vapor
Density and Water Flux in KH20 Eddy-
Covariance Systems ........................................... D-1
D.1 Fundamental Equation .................................................................... D-1
D.2 Working Equation ........................................................................... D-2
D.3 Eddy-Covariance Water Flux.......................................................... D-2
D.4 Frequency Response of KH20......................................................... D-3
D.5 References....................................................................................... D-4
Figures
6-1. Mounting KH20 to a tripod..................................................................4
6-2. Proper mounting position of the electronics box..................................5
6-3. Attaching cables to the electronics box................................................6
A-1. KH20 ln(mV) vs. Vapor Density .................................................... A-2
C-1. Example screen from CRBasic Editor showing user-defined
configuration constants...............................................................C-13
C-2. Custom keypad menu; arrows indicate submenus..........................C-14
Tables
6-1. Wire Color, Function, and Data Logger Connection............................6
6-2. KH20 Calibration Ranges ....................................................................7
A-1. Linear Regression Results for KH20 ln(mV) vs. Vapor Density .... A-2
A-2. Final Calibration Values for KH20 ................................................. A-3
C-1. Default Wiring for Required Sensors...............................................C-3
C-2. Default Wiring for CS106 Barometer ..............................................C-4
C-3. Default Wiring for Fine Wire Thermocouple...................................C-4

Table of Contents
iii
C-4. Default Wiring for GPS Receiver ....................................................C-5
C-5. Default Wiring for Radiation Measurement Option 1......................C-5
C-6. Default Wiring for Radiation Measurements Option 2 ....................C-6
C-7. A21REL-12 Wiring..........................................................................C-8
C-8. CNF4 Wiring....................................................................................C-8
C-9. Default Wiring for Precipitation Gage .............................................C-9
C-10. Default Wiring for Soil Thermocouple Probes ................................C-9
C-11. Default Wiring for Soil Water Content Probes ..............................C-10
C-12. Default Wiring for Non-Calibrating Soil Heat Flux Plates ............C-10
C-13. Default Wiring for Soil Heat Flux Plates (Self Calibrating) ..........C-11
C-14. Station Variables with Descriptions ...............................................C-15
C-15. microSD Flash Card Fill Times with 10Hz Measurement Rate .....C-19
C-16. Data Output Tables ........................................................................C-20
C-17. Data Fields in the Time_Series Data Output Table........................C-21
C-18. Data Fields in the Diagnostic Output Table ...................................C-22
C-19. Data Fields in the Monitor_CSAT3B Output Table.......................C-22
C-20. Data Fields in the Flux_AmeriFluxFormat Output Table ..............C-22
C-21. Data Fields in the Flux_CSFormat Data Output Table ..................C-25
C-22. Data Fields in the Flux_Notes Output Table..................................C-29
CRBasic Example
B-1. CR3000 Program to Measure Water Vapor Fluctuations.................B-1

1
KH20 Krypton Hygrometer
1. Introduction
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.
2. Precautions
•READ AND UNDERSTAND the Safety section at the back of this
manual.
•Although the KH20 is rugged, it should be handled as precision scientific
instrument.
3. Initial Inspection
•Upon receipt of the KH20, inspect the packaging and contents for damage.
File damage claims with the shipping company.
•The model number and cable length are printed on a label at the
connection end of the cable. Check this information against the shipping
documents to ensure the correct product and cable length are received (see
Section 3.1, Components (p. 1)).
3.1 Components
The KH20 sensor consist of a sensor head with 2 m (6 ft) cables and an
electronics box. The following are also shipped with the KH20:
•KH20CBL-L25 Power/Signal cable with 8 m (25 ft) length. If a
longer cable is desired, order a KH20CBL-L replacement cable and
specify the desired length after -L (for example KH20CBL-L50).
•1/2 Unit Desiccant Bag
•Rain Shield
•Horizontal Mounting Boom (51 cm 20 mm DN (20-inch 3/4 IPS)
threaded aluminum pipe)
•3/4 x 3/4 in. Nu-Rail Crossover Fitting
•4 mm (5/32 in) Allen Wrench
4. Overview
The KH20 is a krypton hygrometer for measuring water vapor fluctuations in
the air. The name KH20 (KH-twenty) was derived from KH2O (K-H2O), and
the sensor has been known with this name since 1985. It is typically used with

KH20 Krypton Hygrometer
2
the CSAT3B 3-D sonic anemometer for measuring latent heat flux (LE), using
eddy-covariance technique.
The KH20 sensor uses a krypton lamp that emits two absorption lines: major
line at 123.58 nm and minor line at 116.49 nm. Both lines are absorbed by
water vapor, and a small amount of the minor line is absorbed by oxygen. The
KH20 is not suitable for absolute water vapor concentration measurements due
to its signal offset drift.
The KH20 heads are sealed and will not suffer damage should they get wet. In
addition, the electronics box and the connectors are housed inside a rain shield
that protects them from moisture. The KH20 is suitable for long-term
continuous outdoor applications.
The KH20 sensor is comprised of two main parts: the sensor head and the
electronics box. The sensor head comes with cables that connect the sensor to
the electronics, a power/signal cable, and mounting hardware.
Discussion on the principles and theory of measurement is
included in Appendix A, Calibrating KH20 (p. A-1).
Features:
•High frequency response suitable for eddy-covariance applications
•Well-suited for long-term, unattended applications
•Compatible with Campbell Scientific CRBasic data loggers: CR6,
CR3000, CR1000X, CR800 Series, CR1000, CR5000, and
CR9000(X)
5. Specifications
5.1 Measurements
Calibration Range: 1.7 to 19.5 g/m3(nominal)
Frequency Response:100 Hz
Operating Temperature Range: –30 to 50 °C
5.2 Electrical
Supply Voltage: 10 V to 16 VDC
Current Consumption: 20 mA max at 12 VDC
Power Consumption: 0.24 Watts
Output Signal Range: 0 to 5 VDC
5.3 Physical
Dimensions
Sensor Head: 29 x 23 x 3 cm (11.5 x 9 x 1.25 in)
Electronics Box: 19 x 13 x 5 cm (7.5 x 5 x 2 in)
Rain Shield with Mount: 29 x 18 x 6.5 cm (11.5 x 7 x 2.5 in)
Mounting Pipe: 50 cm (20 in)
Carrying Case: 64 x 38 x 18 cm (25 x 15 x 7 in)
NOTE

KH20 Krypton Hygrometer
3
Weight
Sensor Head: 1.61 kg (3.55 lb)
Electronics Box: 0.6 kg (1.4 lb)
Rain Shield with Mount: 2.2 kg (4.75 lb)
Mounting Pipe with Nu-rail: 0.45 kg (1.0 lb)
Carrying Case: 4.3 kg (9.45 lb)
Shipping: 9.2 kg (20.15 lb)
6. Installation
6.1 Siting
When installing the KH20 sensor for latent heat flux measurement in an eddy-
covariance application, proper siting, sensor height, sensor orientation and
fetch are important.
6.2 Mounting
6.2.1 Parts and Tools Needed for Mounting
The following user-supplied hardware is required to mount the KH20 sensor:
1. Tripod (CM115 standard) or tower
2. Campbell Scientific crossarm (CM204 standard)
3. 3/4-inch IPS Aluminum Pipe, 12 inches long
4. 3/4-inch-by-1-inch Nu-Rail Crossover Fitting
5. Small Phillips and flat-head screwdrivers
6. 1/2-inch wrench
6.2.2 Mounting the KH20 Sensor
Mount the KH20 sensor head as follows:
1. Attach the 51 cm (20 in) mounting boom to the KH20.
2. Mount a crossarm to a tripod or tower.
3. Mount the 12-inch-long pipe to a crossarm via 1-inch-by-3/4-inch Nu-Rail
Crossover Fitting.
4. Mount the KH20 onto the 30 cm (12 in) pipe using a 3/4-inch-by-3/4-inch
Nu-Rail Crossover Fitting. Mount the KH20 such that the source tube, the
longer of the two tubes, is positioned on top, as shown in FIGURE 6-1.
Use cable ties to secure loose cables to the tripod or tower mast.

KH20 Krypton Hygrometer
4
FIGURE 6-1. Mounting KH20 to a tripod.
6.2.3 Mounting the Electronics Box
Mount the electronics box as follows:
1. Remove the front cover of the rain shield by loosening the two pan-head
screws on the bottom front of the rain shield, and then pushing the cover
all the way up, and sliding it out.
It will be difficult to mount the rain shield to a mast with the front
cover on, since the 1/2-inch nut holding the bottom U-bolt is
located inside the rain shield.
2. Before mounting the rain shield to a tripod, first mount the electronics box
inside the rain shield. Remove the four pan-head screws from the back
panel of the rain shield. Align the electronics box and use the four pan-
head screws to secure the electronics box onto the back panel. Make sure
the electronics box is pushed all the way up, and the screws are positioned
at the bottom of the mounting slot on the electronics box (see FIGURE
6-2). This will provide enough room to attach the connectors to the bottom
of the electronics box later.
NOTE

KH20 Krypton Hygrometer
5
FIGURE 6-2. Proper mounting position of the electronics box.
If the electronics box is not pushed all the way up during
mounting, you will not have enough room to attach the connectors
to the bottom of the electronics box, as the U-bolt for the rain
shield will block the position of the connectors.
3. Mount the rain shield onto the tripod or tower mast using the U-bolt
provided. Make sure that the distance between the KH20 sensor head and
the rain shield is within 5 feet so that the cables from the sensor head will
be within reach of the electronics box. Also make sure that the rain shield
is mounted vertically with an opening pointing downward so that the rain
will effectively run down the rain shield and not penetrate inside.
NOTE

KH20 Krypton Hygrometer
6
4. Connect the three cables to the bottom of the electronics box around the
U-bolt on the rain shield (see FIGURE 6-3). If there is not enough room
for the connectors around the U-bolt, make sure the electronics box is
mounted at a highest possible position (see step 2).
FIGURE 6-3. Attaching cables to the electronics box.
5. Place the front cover back on the rain shield and tighten the two pan-head
screws to secure it in place.
6. Gather any loose cables and tie them up, using cable ties, onto the tripod or
tower mast.
6.3 Wiring
TABLE 6-1. Wire Color, Function, and Data Logger Connection
Wire Wire Label Data Logger Connection Terminal
White Signal
U configured for differential input1,
DIFF H (differential high, analog-
voltage input)
Black (from
white/black set)
Signal
Reference
U configured for differential input1, 2,
DIFF L (differential low, analog-
voltage input) 2
Red Power 12V 12V
Black (from
red/black set)
Power
Ground G
Clear Shield
⏚
(analog ground)
1U terminals are automatically configured by the measurement instruction.
2Jumper to ⏚with a user-supplied wire.

KH20 Krypton Hygrometer
7
6.4 Data Logger Programming
The KH20 sensor outputs 0 to 5 VDC analog signal. These signals can be
measured using the VoltDiff instruction on the CRBasic data loggers.
Programming basics for CRBasic data loggers are in the following sections.
Complete program examples for select CRBasic data loggers can be found in
Appendix B, Example Program (p. B-1).
6.4.1 KH20 Calibration
Each KH20 is calibrated over a vapor range of approximately 2 to 19 g/m3. The
calibration is performed twice under the following two conditions: window
clean, and scaled. The water vapor absorption coefficient for three different
vapor ranges are calculated from the collected calibration data: full range, dry
range, and wet range. TABLE 6-2 shows a sample of the KH20 vapor ranges
over which three different water vapor absorption coefficients are calculated.
See Appendix A, Calibrating KH20 (p. A-1), for more information on KH20
calibration.
TABLE 6-2. KH20 Calibration Ranges
Ranges Vapor Density (g/m3)
Full Vapor Range 2 – 19
Dry Vapor Range 2 – 9.5
Wet Vapor Range 8.25 – 19
Before the water vapor absorption coefficient, kw, is entered into the data
logger program for the KH20, the following decisions must be made:
•Will the windows be allowed to scale?
•What vapor range is appropriate for the site?
Once the decision is made, the appropriate kwcan be chosen from the
calibrations sheet. The calibration sheet also contains the path length, x, for a
specific KH20. Using the water vapor absorption coefficient for either the dry
or the wet vapor range will produce more accurate measurements than using
that for the full range. If the vapor range of the site is unknown, or if the vapor
range is on the border line between the dry and the wet vapor ranges, the full
range should be used.
7. Maintenance and Calibration
The KH20 sensor is designed for continuous field application and requires little
maintenance. The tube ends for the KH20 have been sealed with silicone
elastomer using an injection-mold method. Therefore, the tubes are protected
from water damage, and the KH20 continues to make measurements under
rainy or wet conditions. If the water tends to pool up on the tube window and
blocks the signal, turn the sensor head at an angle so as to shed the water off
the tube window. The rain shield protects the electronics box and the
connectors from moisture.

KH20 Krypton Hygrometer
8
7.1 Visual Inspection
•Make sure the optical windows are clean.
•Inspect the cables and connectors for any damage or corrosion. If you see
a discoloration on the white co-axial cable, you may suspect that the cable
has water damage.
7.2 Testing the Source Tube
The source tube is the longer of the two tubes. Check to see if the source tube
is working properly by performing the following test.
First, make sure the UV light is emitted from the source tube. To do this, you
may look into the source tube (the longer of the two tubes), and you should see
a bright blue light emitted from it.
Avoid looking into the source tube for an extended period of time
when the KH20 is powered on to minimize the prolonged
exposure to the UV light.
If you see a faint or flickering blue light, perform the following test.
Check the current drain on the KH20
Typical current drain for the KH20 during normal operation should be
15 ~ 20 mA. The current drain of around 5 mA or less indicates the
problem on the source tube. Obtain an RMA from Campbell Scientific
and send the unit in for repair.
Check the voltage signal output from the KH20
If the voltage output reading is below 50 mV, you may have problems
with either the source tube or the detector tube (Section 7.3, Testing the
Detector Tube (p. 8)).
7.3 Testing the Detector Tube
If the source tube tests fine but the output from KH20 is still in question,
perform the following test. Prepare a piece of paper and insert it between the
source tube and the detector tube to completely block the optical path. You
should see an immediate decrease in the voltage reading, and it should go close
to zero. No noticeable change in the voltage output, when the optical path is
completely blocked, indicates a problem in the detector tube. If the decrease in
the voltage reading takes place but the reading remains below 50 mV, when the
paper is removed from the optical path, the source tube may be at fault. Obtain
an RMA from Campbell Scientific and send the unit in for repair.
7.4 Managing the Scaling of KH20
The KH20 cannot be used to measure an absolute concentration of water vapor,
because of scaling on the source tube windows caused by disassociation of
atmospheric continuants by the ultra violet photons (Campbell and Tanner,
NOTE

KH20 Krypton Hygrometer
9
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.
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).
NOTE

A-1
Appendix A. Calibrating KH20
A.1 Basic Measurement Theory
The KH20 uses an empirical relationship between the absorption of the light
and the material through which the light travels. This relationship is known as
the Beer’s law, the Beer-Lambert law, or the Lambert-Beer law. According to
the Beer’s law, the log of the transmissivity is anti-proportional to the product
of the absorption coefficient of the material, k, the distance the light travels, x,
and the density of the absorbing material, ρ. The KH20 sensor uses the UV
light emitted by the krypton lamp: major line at 123.58 nm and the minor line
at 116.49. As the light travels through the air, both the major line and the minor
line are absorbed by the water vapor present in the light path. This relationship
can be rewritten as follows, where kwis the absorption coefficient for water
vapor, xis the path length for the KH20 sensor, and ρwis the water vapor
density.
ww
xk
eT
ρ −
=
A-1
If we express the transmissivity, T, in terms of the light intensity before and
after passing through the material as measured by the KH20 sensor, Vand V0,
respectively, we obtain the following equation.
ww xk
e
V
V
ρ −
=
0
A-2
Taking the natural log of both sides, and solving for the density, ρw, yields the
following equation.
)ln(ln
1
0
VV
xkw
w−
−
=
ρ
A-3
If the path length, x, and the absorption coefficient for water, kware known, it
becomes possible to measure the water vapor density ρw, by measuring the
signal output, V, from KH20.
A.2 Calibration of KH20
The KH20 calibration process is to find the absorption coefficient of water
vapor, kw. To do this, we rewrite the equation A-3, and solve for ln(V).
0
lnln VxkV
ww
+−= ρ
A-4
It now becomes obvious from the equation A-4 that there is a linear
relationship between the natural log of the KH20 measurement output, lnV, and
the water vapor density, ρw. FIGURE A-1 shows the plot of the equation A-4
after we ran a KH20 over a full calibration vapor range.

Appendix A. Calibrating KH20
A-2
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, kwx. TABLE A-1 shows the result of linear regression
analysis. The slope is the product of the absorption coefficient of water vapor,
kw, and the KH20 path length, x.
TABLE A-1. Linear Regression Results for KH20 ln(mV)
vs. Vapor Density
Description Values
Slope (xkw) –0.205
Y Intercept (ln(V0) 8.033
If we substitute these values, along with the measured lnV into equation A-3,
we can obtain the water vapor density, ρw. Campbell Scientific performs the
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 kwvalues for each sub range, as well as for the full
range. If you know the vapor density range for your site, it is recommended
that you select the coefficient, kw, that is appropriate for your site, the dry range
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 A-2 shows the final calibration values the KH20
calibration certificate contains. The data shown in TABLE A-2 is from an
actual KH20.
4
4.5
5
5.5
6
6.5
7
7.5
8
1.74 3.02 4.17 5.44 6.71 7.95 9.2 10.47 11.69 12.9 14.22 15.46 16.78 18.04 19.25
KH2O Output (mV)
Vapor Density (g/m3)

Appendix A. Calibrating KH20
A-3
TABLE A-2. Final Calibration Values for KH20
Vapor Range
(g/m3)
Slope
(xkw)
Y Intercept
ln (V0)
Coefficient
(kw)
Full Range 1.74 ~ 19.25 -0.205 3087 -0.144
Dry Range 1.74 ~ 9.20 -0.216 3259 -0.151
Wet Range 7.95 ~ 19.25 -0.201 2899 -0.141

B-1
Appendix B. Example Program
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 does not monitor absolute water vapor concentration.
CRBasic Example B-1. CR3000 Program to Measure Water Vapor Fluctuations
'CR3000 Series Data Logger
'This data logger 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 Description
'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)
' data logger POWER IN 12 (red)
'NEG KH20 power- (black)
' KH20 power shield (clear)
' data logger 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].
'*** Variables ***
Public panel_temp
Public batt_volt
Public kh(2)
Public rho_w
Alias kh(1) = kh_mV
Alias kh (2) = ln_kh
Units panel_temp = deg_C
Units batt_volt = volts
Units kh_mV = mV
NOTE

Appendix B. Example Program
B-2
Units ln_kh = ln_mV
Units rho_w = g/m^3
'*** Data Output Tables ***
'Processed data
DataTable (stats,True,-1)
DataInterval (0,OUTPUT_INTERVAL,Min,10)
Minimum (1,batt_volt,FP2,False,False)
Average (1,panel_temp,FP2,False)
Average (2,kh(1),IEEE4,False)
EndTable
'Raw time-series data.
DataTable (ts_data,True,-1)
DataInterval (0,SCAN_INTERVAL,mSec,100)
Sample (1,kh_mV,IEEE4)
EndTable
'*** Program ***
BeginProg
Scan (SCAN_INTERVAL,mSec,3,0)
'data logger panel temperature.
PanelTemp (panel_temp,250)
'Measure battery voltage.
Battery (batt_volt)
'Measure KH20.
VoltDiff (kh_mV,1,mV5000,1,TRUE,200,250,1,0)
ln_kh = LOG(kh_mV)
rho_w = ln_kh/xkw
CallTable stats
CallTable ts_data
NextScan
EndProg

C-1
Appendix C. EasyFlux®DL CR6KH20
C.1 Introduction
EasyFlux®DL CR6KH20 is a CRBasic program that enables a CR6 data
logger, along with a KH20 and CSAT3B, to collect fully corrected fluxes of
latent heat (H2O), sensible heat, and momentum. The program processes the
EC data using commonly used corrections in the scientific literature. The
program can also calculate the ground surface heat flux and energy closure by
adding an optional suite of energy balance sensors. Because the energy balance
sensors require more analog terminals than the CR6 has, the program supports
the addition of a VOLT116 (or CDM-A116) analog terminal expansion
module.
Specifically, the program supports data collection and processing from the
following sensors.
REQUIRED SENSORS:
KH20 Krypton Hygrometer (qty 1)
CSAT3B Sonic Anemometer (qty 1)
Temperature/Relative Humidity (RH) Probe (qty 1). Supported Models:
oHMP155A
oEE181
OPTIONAL SENSORS:
CS106 Barometer (qty 0 to 1)
FW3 Fine Wire Thermocouple (qty 0 to 1)
GPS16X-HVS GPS Receiver (qty 0 to 1)
Radiation measurements
oOption 1
−NR-LITE2 Net Radiometer (qty 0 to 1)
−CS301 or CS320 Pyranometer (qty 0 to 1)
−CS310 Quantum Sensor (qty 0 to 1)
−SI-111 Infrared Radiometer (qty 0 to 1)
oOption 2
−SN500SS, or NR01, or CNR4 4-Way Radiometer
(qty 0 to 1; if using CNR4, the CNF4 Ventilation
and Heating Unit is also supported)
TE525MM Rain Gage (qty 0 to 1)
TCAV Soil Thermocouple Probe (qty 0 to 3)
Soil Water Content Reflectometer (qty 0 to 3)
oCS650
oCS655
Soil Heat Flux Plates
oOption 1: HFP01 plates (qty 0 to 3)
oOption 2: HFP01SC self-calibrating plates (qty 0 to 3)
It may be possible to customize the program for other sensors or
quantities in configurations not described here. Contact Campbell
Scientific for more information.
NOTE
EasyFlux is
a registered trademark of Campbell Scientific, Inc.

Appendix C. EasyFlux®DL CR6KH20
C-2
The VOLT116 and CDM-A116 are functionally the same,
however their OSes are not interchangeable. If updating an OS,
make sure it is for the correct model.
C.2 Precautions
EasyFlux DL CR6KH20 requires the CR6 to have operating system (OS)
version 09.02 or newer. If using a VOLT116, it must have OS v.01 or
newer, or if using a CDM-A116, it must have v.06 or newer.
The program applies the most common EC corrections to fluxes. However, the
user should determine the appropriateness of the corrections for their site.
Campbell Scientific always recommends saving time-series data in the event
reprocessing of raw data is warranted. Further, the user should determine
the quality and fitness of all data for publication, regardless of whether
said data were processed by EasyFlux DL CR6KH20 or another tool.
As EasyFlux DL CR6KH20 is not encrypted, users have the ability to view and
edit the code. However, Campbell Scientific does not guarantee the
function of an altered program.
C.3 Wiring
When wiring the sensors to the data logger or VOLT116, the default wiring
schemes, along with the number of instruments EasyFlux DL CRKH20
supports, should be followed if the standard version of the program is being
used. TABLE C-1 through TABLE C-13 present the wiring schemes.
A KH20 and CSAT3B are the only required sensors for the program. The
additional sensors described in the following tables are optional, although the
CS106 and FW3 are recommended. Many of the optional sensors are wired to a
VOLT116 (or CDM-A116) module, which effectively increases the CR6
analog terminals. If one or more of the optional sensors are not used, the data
logger or VOLT116 terminals assigned to those sensor wires should be left
unwired.
If the standard data logger program is modified, the wiring
presented in TABLE C-1 may no longer apply. In these cases,
refer directly to the program code to determine proper wiring.
If using an analog expansion module, all wiring and connections
are the same whether using a VOLT116 or a CDM-A116.
Therefore, throughout this appendix, the wiring terminals are only
listed for the VOLT116.
NOTE
NOTE
NOTE