Soil Heat Flux Plates—Hukseflux HFP01 and HFP01SC

Hukseflux HFP01 soil heat flux plates measure heat exchange across the plane of the plate and provide analog data to the Sutron 9210B datalogger. Here we provide basic installation and operation guidelines for using the HFP01 in LI-COR eddy covariance systems running Biomet_100 and Biomet_101. For complete operating instructions refer to the manufacturer's instructions at: http://www.hukseflux.com/products/heatFlux/hfp01.html

HFP01 Specifications:
Nominal Sensitivity 50 μV/W/m2
Typical Range: -100 to 300 W/m2
Nominal Resistance: 2 ohms
Temperature Range: -30 to + 70 °C
Sensor Thermal Resistance: <6.25 x 10-3 km2/W
Measurement Range: ±2000 W/m2
Expected Accuracy: Within -5% to +15% in most soils
Power Consumption (HFP01): 0 W

Installing the Heat Flux Plates

  1. Siting Heat Flux Plates.
  2. In a typical installation, three or more heat flux plates are needed in order to ensure good representation of the site.
    • Place each heat flux plate in a shallow pit in soil that is representative of the site.
    • More sensors may be needed if the soil is highly variable.
    • Heat flux plates and soil moisture sensors and temperature sensors can be placed in the same excavation.
  4. Soil heat flux plates should be installed in the vicinity of the eddy covariance tower.
  5. Install Heat Flux Plates
  6. Excavate a small hole with a smooth, undisturbed side. Keep the excavated soil as an intact block if possible. Make a horizontal slit in the smooth side of the excavation 5 cm below the soil surface.
  7. Bury soil heat flux plates at a depth of about 5 cm.
  8. Insert soil heat flux plates into the slot.
  9. With the red side facing up toward the sky, gently insert the heat flux plate in the slit until it is completely covered by soil. Be sure the plate is in full contact with the soil and that there are no air pockets around it. Bury a length of the sensor leads to prevent thermal conduction through the wires. Fill the hole with the excavated soil.
  1. Wire HFP01 Heat Flux Plates to the Datalogger.
  2. HFP01 heat flux plates are supported by programs Biomet_100 and Biomet_101. For custom datalogger programs, use the HeatFlux block and configure it as described in Soil Heat Flux Plates (Hukseflux HFP01).
  3. Route cables through an opening in the bottom of the enclosure.Note: Route the sensor cable(s) through an opening in the enclosure prior to installing the leads in the terminal strip.
  5.   AIO1 Terminal
    Desc. Color Plate 1 Plate 2 Plate 3
    Shield Black 1 (AGND) 4 (AGND) 8 (AGND)
    Signal White 2 (CH1) 5 (CH3) 9 (CH5)
    Ref. Green 3 (CH2) 6 (CH4) 10 (CH6)
  6. Enter the Calibration Data.
  7. Each soil heat flux plate has a unique calibration constant that is provided by Hukseflux. It is printed on the sensor's cable label and given on a calibration sheet provided with the sensor.
  8. The calibration factor (sensitivity) for each sensor, which is in units of μV/W m-2, should be entered directly into the datalogger software.
  9. Click the Data tab, select the soil heat flux plate (e.g., SOILHF1), then click Change.
  11. Enter the sensitivity from the cable label and click OK. In this example, the sensitivity is 60.7 μV/W m-2. Repeat this for the remaining soil heat flux plates.

Retrieving Data

If the system is configured to log biomet data in .ghg files for processing in EddyPro software or the SmartFlux System, data are stored on the removable USB storage device. Refer to the Biomet Instruction Manual for details.

Maintenance

  • Check the devices regularly by observing the data they provide.
  • Periodically check the wire leads for rodent damage.
  • Recalibrate the sensors every two years according to the manufacturer's instructions.