Campbell Scientific HFP01SC User Manual
INSTRUCTION MANUAL
Model HFP01SC Self-Calibrating
Copyright © 2002- 2014
Soil Heat Flux Plate
Revision: 3/14
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Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
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1. Introduction ................................................................. 1
2. Cautionary Statements ............................................... 1
3. Initial Inspection ......................................................... 1
4. Overview ...................................................................... 1
5. Specifications ............................................................. 2
6. Installation ................................................................... 3
6.1 Placement in Soil.................................................................................. 3
6.2 Wiring .................................................................................................. 6
6.3 Programming ........................................................................................ 6
Example 1. Sample CR3000 Program Using a Differential
6.3.1
Measurement Instruction ........................................................... 6
6.3.2 Example 2. Sample CR10(X) Program Using a Single-Ended
Measurement Instruction ........................................................... 9
6.3.3 Example 3. Sample CR23X Program Using a Differential
Measurement Instruction ......................................................... 13
6.3.4 Example 4. Sample CR10X Program Using External Power
and Relay ................................................................................. 17
6.4 Soil Heat Flux and Storage ................................................................. 22
6.5 In-Situ Calibration Theory ................................................................. 23
7. Maintenance .............................................................. 24
8. References ................................................................ 24
Figures
6-1. Placement of heat flux plates ............................................................... 3
6-2. HFP01SC plate ..................................................................................... 4
Tables
6-1. Datalogger Connections for a Single-Ended Measurement ................. 5
6-2. Datalogger Connections for a Differential Measurement ..................... 5
6-3. Wiring for Example 1 ........................................................................... 6
6-4. Wiring for Example 2 ........................................................................... 9
6-5. Wiring for Example 3 ......................................................................... 13
6-6. Sensor Wiring for Example 4 ............................................................. 17
6-7. Datalogger-to-A21REL-12 Wiring for Example 4 ............................. 17
6-8. Hukseflux and Campbell Scientific Variable Names ......................... 24
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Table of Contents
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Model HFP01SC
Self-Calibrating Soil Heat Flux Plate
1. Introduction
The HFP01SC Self-Calibrating Heat Flux Sensor measures soil heat flux,
typically for energy-balance or Bowen-ratio flux systems. It is intended for
applications requiring the highest possible degree of measurement accuracy.
At least two sensors are required for each site to provide spatial averaging.
Sites with heterogeneous media may require additional sensors.
Before installing the HFP01SC, please study
• Section 2, Cautionary Statements
• Section 3, Initial Inspection
The installation procedure is provided in Section 6, Installation.
2. Cautionary Statements
• Care should be taken when opening the shipping package to not damage or
cut the cable jacket. If damage to the cable is suspected, consult with a
Campbell Scientific applications engineer.
• Although the HFP01SC is rugged, it should be handled as a precision
scientific instrument.
3. Initial Inspection
• Upon receipt of the HFP01SC, 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.
• The HFP01SC is shipped with a calibration sheet and an instruction
manual or a ResourceDVD.
4. Overview
The HFP01SC Soil Heat Flux plate consists of a thermopile and a film heater.
The thermopile measures temperature gradients across the plate. During the insitu 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.
1
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
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 CS650, CS655, or 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.
The sensor’s cable can terminate in:
• Pigtails that connect directly to a Campbell Scientific datalogger
(option –PT).
• Connector that attaches to a prewired enclosure (option –PW). Refer
to www.campbellsci.com/prewired-enclosures for more information.
5. Specifications
Features:
• Corrects for errors due to differences in thermal conductivity between
the sensor and the surrounding medium, temperature variations, and
slight sensor instabilities
• Compatible with most of our dataloggers
• Uses Van den Bos-Hoeksema self-calibration method to provide
high-degree of measurement accuracy
Compatibility
Dataloggers: CR800 series
CR1000
CR3000
CR5000
CR9000(X)
CR7X
CR10(X)
CR23X
21X
Operating Temperature: –30° to +70°C
Storage Temperature: –30° to +70°C
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Plate Thickness: 5 mm (0.2 in)
Plate Diameter: 80 mm (3.15 in)
Average Power Consumption: 0.02 to 0.04 W
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
Partial emplacement of the HFP01SC and the TCAV
Sensor: Thermopile and film heater
Heater Voltage Input: 9 to 15 Vdc
Heater Voltage Output: 0 to 2 Vdc
Expected Accuracy: ±3% of reading
6. Installation
6.1 Placement in Soil
Sensitivity (nominal): 50 µV W
Sensor Resistance (nominal): 2 Ω
Heater Resistance (nominal): 100 Ω
Duration of Calibration: ±3 min. @ 1.5 W; typically done every 3 to
6 hours
Weight without Cable: 200 g (7.05 oz)
The HFP01SC soil heat flux plates, the TCAV averaging soil temperature
probes, and the CS616, Water Content Reflectometer, are installed as shown in
FIGURE 6-1.
–1 m–2
sensors is shown for illustration purposes. All sensors
must be completely inserted into the soil face before
the hole is backfilled.
FIGURE 6-1. Placement of heat flux plates
3
Model HFP01SC Self-Calibrating Soil Heat Flux Plate
NOTE
CAUTION
Signal (White)
Signal Reference (Green)
Shield (Clear)
Heater Resis
Heater Resistor Signal Reference (Purple)
Shield (Clear)
Power (Red)
Power Reference (Black)
The location of the heat flux plates and thermocouples should represent the
area of 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 to ensure replacement 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.
Install the HFP01SC in the soil such that the side with the text
“this side up” is facing the sky.
In order for the HFP01SC to make quality soil heat flux
measurements, the plate must be in full contact with the soil.
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 into its original position after all the
sensors are installed.
tor Signal (Yellow)
4
FIGURE 6-2. HFP01SC plate
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