Model HFP01SC Self-Calibrating
Soil Heat Flux Plate
Revision: 8/07
C o p y r i g h t © 2 0 0 2 - 2 0 0 7
C a m p b e l l S c i e n t i f i c , I n c .
Warranty and Assistance
The MODEL HFP01SC SELF-CALIBRATING SOIL HEAT FLUX
PLATE is warranted by CAMPBELL SCIENTIFIC, INC. to be free from
defects in materials and workmanship under normal use and service for twelve
(12) months from date of shipment unless specified otherwise. Batteries have
no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this
warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC,
INC.'s option) defective products. The customer shall assume all costs of
removing, reinstalling, and shipping defective products to CAMPBELL
SCIENTIFIC, INC. CAMPBELL SCIENTIFIC, INC. will return such
products by surface carrier prepaid. This warranty shall not apply to any
CAMPBELL SCIENTIFIC, INC. products which have been subjected to
modification, misuse, neglect, accidents of nature, or shipping damage. This
warranty is in lieu of all other warranties, expressed or implied, including
warranties of merchantability or fitness for a particular purpose. CAMPBELL
SCIENTIFIC, INC. is not liable for special, indirect, incidental, or
consequential damages.
Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone (435) 753-2342. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
HFP01SC Table of Contents
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1. General Description.....................................................1
2. Sensor Specifications .................................................1
3. Installation....................................................................2
4. Wiring............................................................................4
5. Example Programs ......................................................4
6. Soil Heat Flux and Storage .......................................24
7. Maintenance ...............................................................24
8. In-Situ Calibration Theory.........................................24
9. References .................................................................25
Figures
1. Placement of Heat Flux Plates ....................................................................2
2. HFP01SC Plate ...........................................................................................3
Tables
1. Datalogger Connections for a Single-Ended Measurement........................3
2. Datalogger Connections for a Differential Measurement ...........................4
3. Wiring for Example 1 .................................................................................5
4. Wiring for Example 2 .................................................................................9
5. Wiring for Example 3 ...............................................................................14
6A. Wiring for Example 4 ............................................................................17
6B. Wiring for Example 4 ............................................................................17
7. Hukseflux and Campbell Scientific Variable Names ...............................25
i
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Model HFP01SC
Self-Calibrating Soil Heat Flux Plate
1. General Description
The HFP01SC Soil Heat Flux plate consists of a thermopile and a film heater.
The thermopile measures temperature gradients across the plate. During the
in-situ field calibration, the film heater is used to generate a heat flux through
the plate. The amount of power used to generate the calibration heat flux is
measured by the datalogger. Each plate is individually calibrated, at the
factory, to output flux.
In order to measure soil heat flux at the surface, several HFP01SCs are used to
measure the soil heat flux at a depth of eight centimeters. A TCAV Averaging
Soil Thermocouple is used to measure the temporal change in temperature of
the soil layer above the HFP01SC. Finally, a CS616 Water Content
Reflectometer is used to measure the soil water content. The temporal change
in soil temperature and soil water content are used to compute the soil storage
term.
The -L option on the model HFP01SC Soil Heat Flux plate (HFP01SC-L)
indicates that the cable length is user specified. The HFP01SC-L has two
cables; the first cable is the signal output cable and the second is the heater
input cable. Two analog inputs are required to measure the HFP01SC-L This
manual refers to the sensor as the HFP01SC.
2. Specifications
Operating Temperature:
-30°C to +70°C
Storage Temperature:
-30°C to +70°C
Plate Thickness:
5 mm (0.2 in.)
Plate Diameter:
80 mm (3.15 in.)
Power Consumption
During Self Calibration:
1.3 W (108 mA @ 12 vdc)
Sensor:
thermopile and film heater
Measurement Range:
±100 W m-2
Signal Range (nominal):
±5 mV for the above range (sensor), 0 to 2 V
(while the film heater is powered)
Accuracy:
±3% of reading
Sensitivity (nominal):
67 µV W-1 m-2
Sensor Resistance (nominal): 2 Ω
Heater Resistance (nominal): 100 Ω
Current Sensing Resistor:
10Ω 1% 0.25 W
Thermal Conductivity:
0.8 W m-1 K-1
1
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
Up to 1
m
2.5 cm
2 cm
Ground
6 cm
Surface
8 cm
Partial emplacement of the HFP01SC and the TCAV
sensors is shown for illustration purposes. All sensors
must be completely inserted into the soil face before
the hole is backfilled.
FIGURE 1. Placement of Heat Flux Plates
3. Installation
The HFP01SC Soil Heat Flux plates, the TCAV Averaging Soil Temperature
probes, and the CS616 Water Content Reflectometer are installed as shown in
Figure 1.
The location of the heat flux plates and thermocouples should be chosen to be
representative of the area under study. If the ground cover is extremely varied,
it may be necessary to have additional sensors to provide a valid spatial
average of soil heat flux.
Use a small shovel to make a vertical slice in the soil. Excavate the soil to one
side of the slice. Keep this soil intact so that is can be replaced with minimal
disruption.
The sensors are installed in the undisturbed face of the hole. Measure the
sensor depths from the top of the hole. With a small knife, make a horizontal
cut eight centimeters below the surface into the undisturbed face of the hole.
Insert the heat flux plate into the horizontal cut.
NOTE
2
Install the HFP01SC in the soil such that the side with the text
“this side up” is facing the sky.
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
In order for the HFP01SC to make quality soil heat flux
measurements, the plate must be in full contact with the
soil.
CAUTION
Never run the sensors leads directly to the surface. Rather, bury the sensor
leads a short distance back from the hole to minimized thermal conduction on
the lead wire. Replace the excavated soil back into its original position after
all the sensors are installed.
Signal (White)
Signal Reference (Green)
Shield (Clear)
Heater Resistor Signal (Yellow)
SEFLU
UK
X
H
Heater Resistor Signal Reference (Purple)
Shield (Clear)
Power Reference (Black)
H
E
E
Power (Red)
AT
AT
FL U X PL
FIGURE 2. HFP01SC Plate
TABLE 1. Datalogger Connections for a Single-Ended Measurement
Description
Sensor Signal
Color
White
CR10X
Single-Ended Input
CR23X & CR5000
Single-Ended Input
Sensor Signal Reference
Green
AG
Shield
Clear
G
Heater Resistor Signal
Yellow
Single-Ended Input
Heater Resistor Signal
Reference
Shield
Purple
AG
Clear
G
Power
Red
SW12
SW12
Power Reference
Black
G
G
External Power Control
jumper wire
SW12-CTRL to
Control Port
External Power
Control Not Needed
Single-Ended Input
3
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
TABLE 2. Datalogger Connections for a Differential Measurement
Description
Sensor Signal
Color
White
CR10(X)
Differential Input (H)
CR23X & CR5000
Differential Input (H)
Sensor Signal Reference
Green
Differential Input (L)
Differential Input (L)
Shield
Clear
G
Heater Resistor Signal
Yellow
Differential Input (H)
Differential Input (H)
Heater Resistor Signal
Reference
Shield
Purple
Differential Input (L)
Differential Input (L)
Clear
G
Power
Red
SW12
SW12
Power Reference
Black
G
G
External Power Control
Jumper wire
SW12-CTRL to
Control Port
External Power
Control Not Needed
4. Wiring
Connections to Campbell Scientific dataloggers are given in Tables 1 and 2.
The output of the HFP01SC can be measured using a single-ended analog
measurement (Instruction 1 or VoltSE()), however, a differential analog
measurement (Instruction 2 or VoltDiff()) is recommended.
The wiring convention is that the white wire is positive with respect to the
green wire, when energy is flowing through the transducer from the side with
the text “this side up” to the other side.
NOTE
The switched 12 vdc port on the black CR10X wiring panel can
source enough current to calibrate five HFP01SC plates; the
CR23X and CR5000 switched 12 vdc port can be used to
calibrate four HFP01SC plates. If additional HFP01SC plates
are needed an external relay is required to power the additional
plates (see example 4).
For dataloggers without a SW12V output (CR7X, 21X and CR10), a relay
(A21REL-12) is required for the in-situ calibration (see Example 4).
5. Example Programs
The HFP01SC has a nominal calibration of 15 W m-2 mV-1. Each sensor is
accompanied by a calibration certificate. Each sensor also has a unique
calibration label on it. The label is located on the pigtail end of the sensor
leads.
4
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
TABLE 3. Wiring for Example 1
Description
Sensor Signal
Color
White
CR10(X)
1H
Sensor Signal Reference
Green
AG
Shield
Clear
G
Heater Resistor Signal
Yellow
1L
Heater Resistor Signal Reference
Purple
AG
Shield
Clear
G
Power
Red
SW12
Power Reference
Black
External Power Control
G
jumper wire SW12-CTRL to C8
Example 1. Sample CR10(X) Program Using a Single-Ended Measurement Instruction
;{CR10X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;Measure HFP01SC on smaller range.
;
1: Volt (SE) (P1)
1: 1
Reps
2: 22
7.5 mV 60 Hz Rejection Range
3: 1
SE Channel
4: 2
Loc [ shf_mV ]
5: 1
Mult
6: 0
Offset
;Measure HFP01SC on larger range.
;
2: Volt (SE) (P1)
1: 1
Reps
2: 23
25 mV 60 Hz Rejection Range
3: 1
SE Channel
4: 8
Loc [ shf_mV_a ]
5: 1
Mult
6: 0
Offset
;Load in the factory calibration.
;
3: If (X<=>F) (P89)
1: 3
X Loc [ cal
2: 1
=
3: 0
F
4: 30
Then Do
]
5
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
;Factory calibration in W/(m^2 mV) = 1000/sensitivity.
;
4: Z=F (P30)
1: 1
F
; <- Enter the unique calibration here
2: 0
Exponent of 10
3: 3
Z Loc [ cal
]
5: End (P95)
;Use data from the larger measurement range.
;
6: If (X<=>F) (P89)
1: 2
X Loc [ shf_mV ]
2: 4
<
3: -99990
F
4: 30
Then Do
7: Z=X (P31)
1: 8
2: 2
X Loc [ shf_mV_a ]
Z Loc [ shf_mV ]
8: End (P95)
;Apply custom calibration to the raw soil heat flux measurement.
;
9: Z=X*Y (P36)
1: 2
X Loc [ shf_mV ]
2: 3
Y Loc [ cal
]
3: 1
Z Loc [ shf
]
;Output data.
;
10: If time is (P92)
1: 0
Minutes (Seconds --) into a
2: 20
Interval (same units as above)
3: 10
Set Output Flag High (Flag 0)
11: Real Time (P77)
1: 0110
Day,Hour/Minute (midnight = 0000)
12: Resolution (P78)
1: 1
High Resolution
;Do not include the calibration data in the soil heat flux.
;
13: If Flag/Port (P91)
1: 18
Do if Flag 8 is High
2: 19
Set Intermed. Proc. Disable Flag High (Flag 9)
14: Average (P71)
1: 1
Reps
2: 1
Loc [ shf
15: Do (P86)
1: 29
6
]
Set Intermed. Proc. Disable Flag Low (Flag 9)
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
16: Sample (P70)
1: 1
Reps
2: 3
Loc [ cal
]
;Add other processing here.
;Call calibration routine.
;
17: Do (P86)
1: 8
Call Subroutine 8
*Table 2 Program
02: 0
Execution Interval (seconds)
*Table 3 Subroutines
;Calibration routine.
;
1: Beginning of Subroutine (P85)
1: 8
Subroutine 8
;Perform in-situ calibratation.
;
2: If time is (P92)
1: 1
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
3: Z=X (P31)
1: 2
2: 4
X Loc [ shf_mV ]
Z Loc [ mV_0
]
;Begin heating for calibration.
;
4: Do (P86)
1: 48
Set Port 8 High
;Used to filter data during and after calibration.
;
5: Do (P86)
1: 18
Set Flag 8 High
6: End (P95)
;End site calibration three minutes after calibration started.
;
7: If time is (P92)
1: 4
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
7
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
;Measure voltage across current shunt resistor (10 ohm 1% 0.25 W 50
;ppm/deg C) during calibration. This measurement is used to
;compute power.
;
8: Volt (SE) (P1)
1: 1
Reps
2: 25
2500 mV 60 Hz Rejection Range
3: 2
SE Channel
4: 7
Loc [ V_Rf
]
5: .001
Mult
6: 0
Offset
9: Z=X (P31)
1: 2
2: 5
X Loc [ shf_mV ]
Z Loc [ mV_180 ]
;Turn off the soil heat flux plate heater.
;
10: Do (P86)
1: 58
Set Port 8 Low
11: End (P95)
;Stop filtering data.
;
12: If time is (P92)
1: 39
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
13: Do (P86)
1: 28
Set Flag 8 Low
;Compute in-situ calibration.
;
14: Z=X (P31)
1: 2
X Loc [ shf_mV ]
2: 6
Z Loc [ mV_end ]
15: Z=X*Y (P36)
1: 7
X Loc [ V_Rf
]
2: 7
Y Loc [ V_Rf
]
3: 3
Z Loc [ cal
]
16: Z=X*F (P37)
1: 3
X Loc [ cal
2: 128.7
F
3: 3
Z Loc [ cal
]
]
17: Z=X+Y (P33)
1: 4
X Loc [ mV_0
]
2: 6
Y Loc [ mV_end ]
3: 9
Z Loc [ work
]
18: Z=X*F (P37)
1: 9
X Loc [ work
2: .5
F
3: 9
Z Loc [ work
8
]
]
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
19: Z=X-Y (P35)
1: 9
X Loc [ work
]
2: 5
Y Loc [ mV_180 ]
3: 9
Z Loc [ work
]
20: Z=ABS(X) (P43)
1: 9
X Loc [ work
2: 9
Z Loc [ work
]
]
21: Z=X/Y (P38)
1: 3
X Loc [ cal
]
2: 9
Y Loc [ work
]
3: 3
Z Loc [ cal
]
22: End (P95)
23: End (P95)
End Program
-Input Locations1 shf
2 shf_mV
3 cal
4 mV_0
5 mV_180
6 mV_end
7 V_Rf
8 shf_mV_a
9 work
TABLE 4. Wiring for Example 2
Description
Sensor Signal
Color
White
CR23X
9H
Sensor Signal Reference
Green
9L
Shield
Clear
Heater Resistor Signal
Yellow
10H
Heater Resistor Signal Reference
Purple
10L
Shield
Clear
Power
Red
SW12
Power Reference
Black
G
9
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
Example 2. Sample CR23X Program Using a Differential Measurement Instruction
;{CR23X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;Measure HFP01SC on smaller range.
;
1: Volt (Diff) (P2)
1: 1
Reps
2: 21
10 mV, 60 Hz Reject, Slow Range
3: 9
DIFF Channel
4: 2
Loc [ shf_mV ]
5: 1
Mult
6: 0
Offset
;Measure HFP01SC on larger range.
;
2: Volt (Diff) (P2)
1: 1
Reps
2: 25
5000 mV, 60 Hz Reject, Fast Range
3: 9
DIFF Channel
4: 8
Loc [ shf_mV_a ]
5: 1
Mult
6: 0
Offset
;Load in the factory calibration.
;
3: If (X<=>F) (P89)
1: 3
X Loc [ cal
2: 1
=
3: 0
F
4: 30
Then Do
]
;Factory calibration in W/(m^2 mV) = 1000/sensitivity.
;
4: Z=F (P30)
1: 1
F
; <- Enter the unique calibration here
2: 0
Exponent of 10
3: 3
Z Loc [ cal
]
5: End (P95)
;Use data from the larger measurement range.
;
6: If (X<=>F) (P89)
1: 2
X Loc [ shf_mV ]
2: 4
<
3: -99990
F
4: 30
Then Do
7: Z=X (P31)
1: 8
2: 2
8: End (P95)
10
X Loc [ shf_mV_a ]
Z Loc [ shf_mV ]
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
;Apply custom calibration to the raw soil heat flux measurement.
;
9: Z=X*Y (P36)
1: 2
X Loc [ shf_mV ]
2: 3
Y Loc [ cal
]
3: 1
Z Loc [ shf
]
;Output data.
;
10: If time is (P92)
1: 0
Minutes (Seconds --) into a
2: 20
Interval (same units as above)
3: 10
Set Output Flag High (Flag 0)
11: Real Time (P77)
1: 0110
Day,Hour/Minute (midnight = 0000)
12: Resolution (P78)
1: 1
High Resolution
;Do not include that calibration data in the soil heat flux.
;
13: If Flag/Port (P91)
1: 118
Do if Flag 18 is High
2: 19
Set Intermed. Proc. Disable Flag High (Flag 9)
14: Average (P71)
1: 1
Reps
2: 1
Loc [ shf
15: Do (P86)
1: 29
]
Set Intermed. Proc. Disable Flag Low (Flag 9)
16: Sample (P70)
1: 1
Reps
2: 3
Loc [ cal
]
;Add other processing here.
;Call calibration routine.
;
17: Do (P86)
1: 8
Call Subroutine 8
*Table 2 Program
02: 0
Execution Interval (seconds)
*Table 3 Subroutines
;Calibration routine.
;
1: Beginning of Subroutine (P85)
1: 8
Subroutine 8
;Perform in-situ calibratation.
;
11
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
2: If time is (P92)
1: 1
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
3: Z=X (P31)
1: 2
2: 4
X Loc [ shf_mV ]
Z Loc [ mV_0
]
;Begin heating for calibration.
;
4: Do (P86)
1: 49
Turn On Switched 12V
;Used to filter data during and after calibration.
;
5: Do (P86)
1: 118
Set Flag 18 High
6: End (P95)
;End site calibration three minutes after calibration started.
;
7: If time is (P92)
1: 4
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
;Measure voltage across current shunt resistor during calibration.
;This measurement is used to compute power.
;
8: Volt (Diff) (P2)
1: 1
Reps
2: 25
5000 mV, 60 Hz Reject, Fast Range
3: 10
DIFF Channel
4: 7
Loc [ V_Rf
]
5: .001
Mult
6: 0
Offset
9: Z=X (P31)
1: 2
2: 5
X Loc [ shf_mV ]
Z Loc [ mV_180 ]
;Turn off the soil heat flux plate heater.
;
10: Do (P86)
1: 59
Turn Off Switched 12V
11: End (P95)
;Stop filtering data.
;
12: If time is (P92)
1: 39
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
12
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
13: Do (P86)
1: 218
Set Flag 18 Low
;Compute in-situ clibration.
;
14: Z=X (P31)
1: 2
X Loc [ shf_mV ]
2: 6
Z Loc [ mV_end ]
15: Z=X*Y (P36)
1: 7
X Loc [ V_Rf
]
2: 7
Y Loc [ V_Rf
]
3: 3
Z Loc [ cal
]
16: Z=X*F (P37)
1: 3
X Loc [ cal
2: 128.7
F
3: 3
Z Loc [ cal
]
]
17: Z=X+Y (P33)
1: 4
X Loc [ mV_0
]
2: 6
Y Loc [ mV_end ]
3: 9
Z Loc [ work
]
18: Z=X*F (P37)
1: 9
X Loc [ work
2: .5
F
3: 9
Z Loc [ work
]
]
19: Z=X-Y (P35)
1: 9
X Loc [ work
]
2: 5
Y Loc [ mV_180 ]
3: 9
Z Loc [ work
]
20: Z=ABS(X) (P43)
1: 9
X Loc [ work
2: 9
Z Loc [ work
]
]
21: Z=X/Y (P38)
1: 3
X Loc [ cal
]
2: 9
Y Loc [ work
]
3: 3
Z Loc [ cal
]
22: End (P95)
23: End (P95)
End Program
-Input Locations1 shf
2 shf_mV
3 cal
4 mV_0
5 mV_180
6 mV_end
7 V_Rf
8 shf_mV_a
9 work
13
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
TABLE 5. Wiring for Example 3
14
Description
Sensor Signal #1
Color
White
CR5000
11H
Sensor Signal Reference #1
Green
11L
Shield #1
Clear
Sensor Signal #2
White
12H
Sensor Signal Reference #2
Green
12L
Shield #2
Clear
Sensor Signal #3
White
13H
Sensor Signal Reference #3
Green
13L
Shield #3
Clear
Sensor Signal #4
White
14H
Sensor Signal Reference #4
Green
14L
Shield #4
Clear
Heater Resistor Signal #1
Yellow
17H
Heater Resistor Signal Reference #1
Purple
17L
Shield #1
Clear
Power #1
Red
SW12
Power Reference #1
Black
G
Heater Resistor Signal #2
Yellow
18H
Heater Resistor Signal Reference #2
Purple
18L
Shield #2
Clear
Power #2
Red
SW12
Power Reference #2
Black
G
Heater Resistor Signal #3
Yellow
19H
Heater Resistor Signal Reference #3
Purple
19L
Shield #3
Clear
Power #3
Red
SW12
Power Reference #3
Black
G
Heater Resistor Signal #4
Yellow
20H
Heater Resistor Signal Reference #4
Purple
20L
Shield #4
Clear
Power #4
Red
SW12
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
Example 3. Sample CR5000 Program Using a Differential Measurement Instruction
'CR5000 Series Datalogger
Const OUTPUT_INTERVAL = 30
'Online mean output interval in minutes.
Const CAL_INTERVAL = 1440
'HFP01SC insitu calibration interval (minutes).
Const END_CAL = OUTPUT_INTERVAL-1 'End HFP01SC insitu calibration one minute before the next Output.
Const HFP01SC_CAL_1 = 15
'Unique multiplier for HFP01SC #1 (1000/sensitivity).
Const HFP01SC_CAL_2 = 15
'Unique multiplier for HFP01SC #2 (1000/sensitivity).
Const HFP01SC_CAL_3 = 15
'Unique multiplier for HFP01SC #3 (1000/sensitivity).
Const HFP01SC_CAL_4 = 15
'Unique multiplier for HFP01SC #4 (1000/sensitivity).
'*** Variables ***
Public shf(4)
Alias shf(1) = hfp01sc_1
Alias shf(2) = hfp01sc_2
Alias shf(3) = hfp01sc_3
Alias shf(4) = hfp01sc_4
Units shf = W/m^2
Public shf_cal(4)
Units shf_cal = W/(m^2 mV)
'HFP01SC calibration variables.
Dim shf_mV(4)
Dim shf_mV_run(4)
Dim shf_mV_0(4)
Dim shf_mV_180(4)
Dim shf_mV_end(4)
Dim V_Rf(4)
Dim V_Rf_run(4)
Dim V_Rf_180(4)
Dim shf_cal_on
Dim sw12_state
Dim j
'State of the switched 12Vdc port.
DataTable (mean,TRUE,100)
DataInterval (0,OUTPUT_INTERVAL,Min,10)
Average (4,hfp01sc_1,IEEE4,shf_cal_on)
Sample (4,shf_cal(1),IEEE4)
EndTable
Sub hfp01sc_cal
'Begin HFP01SC calibration on a fixed interval.
If ( IfTime (1,CAL_INTERVAL,Min) ) Then
shf_cal_on = TRUE
Move (shf_mV_0(1),4,shf_mV_run(1),4)
sw12_state = TRUE
EndIf
15
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
If ( IfTime (4,CAL_INTERVAL,Min) ) Then
Move (shf_mV_180(1),4,shf_mV_run(1),4)
Move (V_Rf_180(1),4,V_Rf_run(1),4)
sw12_state = FALSE
EndIf
If ( IfTime (END_CAL,CAL_INTERVAL,Min) ) Then
Move (shf_mV_end(1),4,shf_mV_run(1),4)
'Compute new HFP01SC calibration factors.
For j = 1 to 4
shf_cal(j) = (V_Rf_180(j)*V_Rf_180(j)*128.7)/ABS (((shf_mV_0(j)+shf_mV_end(j))/2)-shf_mV_180)
Next j
shf_cal_on = FALSE
EndIf
EndSub
BeginProg
'HFP01SC factory calibration in W/(m^2 mV) = 1000/sensitivity.
shf_cal(1) = HFP01SC_CAL_1
shf_cal(2) = HFP01SC_CAL_2
shf_cal(3) = HFP01SC_CAL_3
shf_cal(4) = HFP01SC_CAL_4
Scan (100,mSec,3,0)
'Measure the HFP01SC soil heat flux plates.
VoltDiff (shf_mV(1),4,mV50C,11,TRUE,200,250,1,0)
'Apply calibration to HFP01SC soil heat flux plates.
For j = 1 to 4
shf(j) = shf_mV(j)*shf_cal(j)
Next j
'Measure voltage across the heater (Rf_V).
VoltSe (V_Rf(1),4,mV5000,33,TRUE,200,250,0.001,0)
'Maintain a 100 sample running average.
AvgRun (shf_mV_run(1),4,shf_mV(1),100)
AvgRun (V_Rf_run(1),4,V_Rf(1),100)
CallTable (mean)
Call hfp01sc_cal
NextScan
EndProg
16
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
TABLE 6A. Wiring for Example 4
Description
Sensor Signal #1
Color
White
CR10X
1H
Sensor Signal #2
White
1L
Sensor Signal #3
White
2H
Sensor Signal #4
White
2L
Sensor Signal #5
White
3H
Sensor Signal #6
White
3L
All Signal References
Green
AG
All Shields
Clear
G
Heater Resistor Signal #1
Yellow
4H
Heater Resistor Signal #2
Yellow
4L
Heater Resistor Signal #3
Yellow
5H
Heater Resistor Signal #4
Yellow
5L
Heater Resistor Signal #5
Yellow
6H
A21REL-12
Heater Resistor Signal #6
Yellow
6L
All Heater Resistor Signal References
Purple
AG
All Shields
Clear
G
Sensor Power #1
Red
REL 1 NO
Sensor Power #2
Red
REL 1 NO
Sensor Power #3
Red
REL 2 NO
Sensor Power #4
Red
REL 2 NO
Sensor Power #5
Red
REL 3 NO
Sensor Power #6
Red
REL 3 NO
All Power Reference
Black
G
TABLE 6B. Wiring for Example 4
Description
Power
CR10X
12V
A21REL-12
+ 12V
Power Reference
G
GROUND
Control
C8
CTRL 1
Control
jumper from CTRL 2 to CTRL 1
Control
jumper from CTRL 3 to CTRL 2
Power
jumper from REL 1 COM to +12V
Power
jumper from REL 2 COM to REL 1 COM
Power
jumper for REL 3 COM to REL 2 COM
17
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
Example 4. Sample CR10X Program Using External Power and Relay
;{CR10X}
;
*Table 1 Program
01: 1
Execution Interval (seconds)
;Measure HFP01SC on smallest range.
;
1: Volt (SE) (P1)
1: 6
Reps
2: 22
7.5 mV 60 Hz Rejection Range
3: 1
SE Channel
4: 7
Loc [ shf_mV_1 ]
5: 1
Mult
6: 0
Offset
;Measure HFP01SC on larger range.
;
2: Volt (SE) (P1)
1: 6
Reps
2: 23
25 mV 60 Hz Rejection Range
3: 1
SE Channel
4: 44
Loc [ shf_mV_1a ]
5: 1
Mult
6: 0
Offset
;Load in the factory calibration.
;
3: If (X<=>F) (P89)
1: 13
X Loc [ cal_1
2: 1
=
3: 0
F
4: 30
Then Do
]
;Factory calibration in W/(m^2 mV) = 1000/sensitivity.
;
4: Z=F (P30)
1: 1
F
;<- Enter the unique calibration for plate 1 here.
2: 0
Exponent of 10
3: 13
Z Loc [ cal_1 ]
18
5: Z=F (P30)
1: 1
2: 0
3: 14
F
Exponent of 10
Z Loc [ cal_2 ]
;<- Enter the unique calibration for plate 2 here.
6: Z=F (P30)
1: 1
2: 0
3: 15
F
Exponent of 10
Z Loc [ cal_3 ]
;<- Enter the unique calibration for plate 3 here.
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
7: Z=F (P30)
1: 1
2: 0
3: 16
F
Exponent of 10
Z Loc [ cal_4 ]
;<- Enter the unique calibration for plate 4 here.
8: Z=F (P30)
1: 1
2: 0
3: 17
F
Exponent of 10
Z Loc [ cal_5 ]
;<- Enter the unique calibration for plate 5 here.
9: Z=F (P30)
1: 1
2: 0
3: 18
F
Exponent of 10
Z Loc [ cal_6 ]
;<- Enter the unique calibration for plate 6 here.
10: End (P95)
11: Beginning of Loop (P87)
1: 0
Delay
2: 6
Loop Count
;Use data from the larger measurement range.
;
12: If (X<=>F) (P89)
1: 7 -X Loc [ shf_mV_1 ]
2: 4
<
3: -99990
F
4: 30
Then Do
13: Z=X (P31)
1: 44 -2: 7 --
X Loc [ shf_mV_1a ]
Z Loc [ shf_mV_1 ]
14: End (P95)
;Apply custom calibration to raw soil heat flux measurement.
;
15: Z=X*Y (P36)
1: 7 -X Loc [ shf_mV_1 ]
2: 13 -Y Loc [ cal_1 ]
3: 1 -Z Loc [ shf_1 ]
16: End (P95)
;Output data.
;
17: If time is (P92)
1: 0
Minutes (Seconds --) into a
2: 20
Interval (same units as above)
3: 10
Set Output Flag High (Flag 0)
18: Real Time (P77)^25251
1: 0110
Day,Hour/Minute (midnight = 0000)
19
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
19: Resolution (P78)
1: 1
High Resolution
;Do not include that calibration data in the soil heat flux.
;
20: If Flag/Port (P91)
1: 18
Do if Flag 8 is High
2: 19
Set Intermed. Proc. Disable Flag High (Flag 9)
21: Average (P71)^21989
1: 6
Reps
2: 1
Loc [ shf_1
22: Do (P86)
1: 29
]
Set Intermed. Proc. Disable Flag Low (Flag 9)
23: Sample (P70)^21779
1: 6
Reps
2: 13
Loc [ cal_1
]
;Add other processing here.
;Call calibration routine.
;
24: Do (P86)
1: 8
Call Subroutine 8
*Table 2 Program
02: 0
Execution Interval (seconds)
*Table 3 Subroutines
;Calibration routine.
;
1: Beginning of Subroutine (P85)
1: 8
Subroutine 8
;Perform in-situ calibratation.
;
2: If time is (P92)
1: 1
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
3: Beginning of Loop (P87)
1: 0
Delay
2: 6
Loop Count
4: Z=X (P31)
1: 7 -2: 19 -5: End (P95)
20
X Loc [ shf_mV_1 ]
Z Loc [ mV_0_1 ]
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
;Begin heating for calibration.
;
6: Do (P86)
1: 48
Set Port 8 High
;Used to filter data during and after calibration.
;
7: Do (P86)
1: 18
Set Flag 8 High
8: End (P95)
;End site calibration three minutes after calibration started.
;
9: If time is (P92)
1: 4
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
;Measure voltage across current shunt resistor during calibration.
;This measurement is used to compute power.
;
10: Volt (SE) (P1)
1: 6
Reps
2: 25
2500 mV 60 Hz Rejection Range
3:
SE Channel
4: 37
Loc [ V_Rf_1 ]
5: .001
Mult
6: 0
Offset
11: Beginning of Loop (P87)
1: 0
Delay
2: 6
Loop Count
12: Z=X (P31)
1: 7 -2: 25 --
X Loc [ shf_mV_1 ]
Z Loc [ mV_180_1 ]
13: End (P95)
;Turn off the soil heat flux plate heaters.
;
14: Do (P86)
1: 58
Set Port 8 Low
15: End (P95)
;Compute in-situ calibration.
;
16: If time is (P92)
1: 39
Minutes (Seconds --) into a
2: 180
Interval (same units as above)
3: 30
Then Do
21
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
17: Do (P86)
1: 28
Set Flag 8 Low
18: Beginning of Loop (P87)
1: 0
Delay
2: 6
Loop Count
19: Z=X (P31)
1: 7 -2: 31 --
X Loc [ shf_mV_1 ]
Z Loc [ mV_end_1 ]
20: Z=X*Y (P36)
1: 37 -X Loc [ V_Rf_1 ]
2: 37 -Y Loc [ V_Rf_1 ]
3: 13 -Z Loc [ cal_1 ]
21: Z=X*F (P37)
1: 13 -X Loc [ cal_1
2: 128.7
F
3: 13 -Z Loc [ cal_1
]
]
22: Z=X+Y (P33)
1: 19 -X Loc [ mV_0_1 ]
2: 31 -Y Loc [ mV_end_1 ]
3: 43
Z Loc [ work
]
23: Z=X*F (P37)
1: 43
X Loc [ work
2: .5
F
3: 43
Z Loc [ work
]
]
24: Z=X-Y (P35)
1: 43
X Loc [ work
]
2: 25 -Y Loc [ mV_180_1 ]
3: 43
Z Loc [ work
]
25: Z=ABS(X) (P43)
1: 43
X Loc [ work
2: 43
Z Loc [ work
]
]
26: Z=X/Y (P38)
1: 13 -X Loc [ cal_1
2: 43
Y Loc [ work
3: 13 -Z Loc [ cal_1
]
]
]
27: End (P95)
28: End (P95)
29: End (P95)
End Program
22
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
-Input Locations1 shf_1 1 1 1
2 shf_2 0 0 0
3 shf_3 0 0 0
4 shf_4 0 0 0
5 shf_5 0 0 0
6 shf_6 0 0 0
7 shf_mV_1 1 5 2
8 shf_mV_2 1 0 1
9 shf_mV_3 1 0 1
10 shf_mV_4 1 0 1
11 shf_mV_5 1 0 1
12 shf_mV_6 1 0 1
13 cal_1 5 5 3
14 cal_2 9 0 1
15 cal_3 9 0 1
16 cal_4 9 0 1
17 cal_5 9 0 1
18 cal_6 9 0 1
19 mV_0_1 9 1 1
20 mV_0_2 1 0 0
21 mV_0_3 0 0 0
22 mV_0_4 0 0 0
23 mV_0_5 0 0 0
24 mV_0_6 0 0 0
25 mV_180_1 1 1 1
26 mV_180_2 0 0 0
27 mV_180_3 0 0 0
28 mV_180_4 0 0 0
29 mV_180_5 0 0 0
30 mV_180_6 0 0 0
31 mV_end_1 1 1 1
32 mV_end_2 0 0 0
33 mV_end_3 0 0 0
34 mV_end_4 0 0 0
35 mV_end_5 0 0 0
36 mV_end_6 0 0 0
37 V_Rf_1 5 2 1
38 V_Rf_2 9 0 1
39 V_Rf_3 9 0 1
40 V_Rf_4 9 0 1
41 V_Rf_5 9 0 1
42 V_Rf_6 17 0 1
43 work
144
44 shf_mV_1a 5 1 1
45 shf_mV_2a 9 0 1
46 shf_mV_3a 9 0 1
47 shf_mV_4a 9 0 1
48 shf_mV_5a 9 0 1
49 shf_mV_6a 17 0 1
23
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
6. Soil Heat Flux and Storage
The soil heat flux at the surface is calculated by adding the measured flux at a
fixed depth, d, to the energy stored in the layer above the heat flux plates. The
specific heat of the soil and the change in soil temperature, ∆Ts, over the
output interval, t, are required to calculate the stored energy.
The heat capacity of the soil is calculated by adding the specific heat of the dry
soil to that of the soil water. The values used for specific heat of dry soil and
water are on a mass basis. The heat capacity of the moist is given by:
C s = ρ b (C d + θ m C w ) = ρ b C d + θ v ρ w C w
θm =
ρw
θv
ρb
(1)
(2)
where CS is the heat capacity of moist soil, ρb is bulk density, ρw is the density
of water, Cd is the heat capacity of a dry mineral soil, θm is soil water content
on a mass basis, θv is soil water content on a volume basis, and Cw is the heat
capacity of water.
This calculation requires site specific inputs for bulk density, mass basis soil
water content or volume basis soil water content, and the specific heat of the
dry soil. Bulk density and mass basis soil water content can be found by
sampling (Klute, 1986). The volumetric soil water content is measured by the
CS616 water content reflectometer. A value of 840 J kg-1 K-1 for the heat
capacity of dry soil is a reasonable value for most mineral soils (Hanks and
Ashcroft, 1980).
The storage term is then given by Eq. (3) and the soil heat flux at the surface is
given by Eq. (4).
S=
∆Ts C s d
t
Gsfc = G8cm + S
(3)
(4)
7. Maintenance
The HFP01SC requires minimal maintenance. Check the sensor leads monthly
for rodent damage.
8. In-Situ Calibration Theory
For detailed information on the theory of the in-situ calibration, see the Theory
section of the Hukseflux manual or visit the application section of the
Hukseflux web site at
http://www.hukseflux.com/heat%20flux/applic&spec.pdf.
Equation 6 in the Hukseflux manual is used to compute a new calibration every
three hours. The heater is on for a total of 180 seconds. Table 7 lists the
24
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
variables used in the Hukseflux manual and those in the example datalogger
programs.
TABLE 7. Hukseflux and Campbell Scientific
Variable Names
Description
Hukseflux
Campbell
Scientific
shf
Soil Heat Flux
Output of Sensor in mV
ϕ
Vsen
1/Sensitivity
1/Esen2
cal
Output of Sensor during
calibration at t=0 seconds
Output of Sensor during
calibration at t=180 seconds
Output of Sensor after
calibration and just before
output
Voltage Across fixed
10 Ω resistor
V (0)
mV_0
V (180)
mV_180
V (360)
mV_end
Vcur
V_Rf
shf_mV
9. References
Hanks, R. J., and G. L. Ashcroft, 1980: Applied Soil Physics: Soil Water and
Temperature Application. Springer-Verlag, 159 pp.
Klute, A., 1986: Method of Soil Analysis. No. 9, Part 1, Sections 13 and 21,
American Society of Agronomy, Inc., Soil Science Society of America,
Inc.
25
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
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26
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