HFP01

The HFP01, manufactured by Hukseflux, measures soil heat flux, typically for energy-balance or Bowen-ratio flux systems. It outputs a voltage signal that is proportional to the heat flux of the surrounding medium. At least two sensors are required for each site to provide spatial averaging. Sites with heterogeneous media may require additional sensors.

The HFP01 uses a thermopile to measure temperature gradients across its plate. Operating in a completely passive way, it generates a small output voltage that is proportional to this differential temperature. Assuming that the heat flux is steady, that the thermal conductivity of the body is constant, and that the sensor has negligible influence on the thermal flow pattern, the signal of the HFP01 is directly proportional to the local heat flux.

The HFP01’s output is in millivolts. To convert this measured voltage to heat flux, it must be divided by the plate’s calibration constant. A unique calibration constant is supplied with each sensor.

Note: In an energy-balance installation, all sensors must be completely inserted into the soil face before the hole is backfilled.